An herb is a plant or plant part used for its scent, flavor, or therapeutic properties. Herbal medicines are one type of dietary supplement. They are sold as tablets, capsules, powders, teas, extracts, and fresh or dried plants. People use herbal medicines to try to maintain or improve their health.

Many people believe that products labeled "natural" are always safe and good for them. This is not necessarily true. Herbal medicines do not have to go through the testing that drugs do. Some herbs, such as comfrey and ephedra, can cause serious harm. Some herbs can interact with prescription or over-the-counter medicines.

If you are thinking about using an herbal medicine, first get information on it from reliable sources. Make sure to tell your health care provider about any herbal medicines you are taking.

Federal law defines dietary supplements as products that: 

• You take by mouth (such as a tablet, capsule, powder, or liquid). 
• Are made to supplement the diet.
• Have one or more dietary ingredients, including vitamins, minerals, herbs or other botanicals, amino acids, enzymes, tissues from organs or glands, or extracts of these. 
• Are labeled as being dietary supplements.

Herbal supplements—sometimes called botanicals—are a type of dietary supplement containing one or more herbs. 

The amount of scientific evidence on dietary supplements varies widely—there is a lot of information on some and very little on others. If you’re considering using a dietary supplement, it’s important to keep the following in mind: 

• Supplements you buy from stores or online may differ in important ways from products tested in research studies. 
• Dietary supplements may interact with your medications or pose risks if you have certain medical problems or are going to have surgery. 
• Many dietary supplements haven’t been tested in pregnant women, nursing mothers, or children. 
• What’s listed on the label of a dietary supplement may not be what’s in the product. For example, some products marketed for weight loss, sexual enhancement, or bodybuilding have been found to contain prescription drugs not allowed in dietary supplements or other ingredients not listed on the label, and some of these ingredients may be unsafe. 
• Rules for manufacturing and distributing dietary supplements are less strict than those for prescription or over-the-counter drugs. Although the U.S. Food and Drug Administration (FDA) requires that companies submit safety data about any new ingredient not sold in the United States in a dietary supplement before 1994, the FDA is not authorized to review dietary supplements for safety and effectiveness before they are marketed.
• In 2023, the FDA launched the Dietary Supplement Ingredient Directory, a webpage where the public can look up ingredients used in products marketed as dietary supplements and find what the FDA has said about that ingredient, as well as whether the agency has taken any action with regard to the ingredient.

Common Names: acai, acai berry, açaí

Latin Names: Euterpe oleracea, Euterpe badiocarpa

Background

• The acai palm tree, native to tropical Central and South America, produces a deep purple fruit. The acai fruit has long been an important food source for indigenous peoples of the Amazon region.
• Acai products have become popular in the United States, where they have been promoted for weight-loss and anti-aging purposes.
• The Federal Trade Commission has taken action against companies that marketed acai weight-loss products in allegedly deceptive ways.
• Acai fruit pulp has been used experimentally as an oral contrast agent for magnetic resonance imaging (MRI) of the digestive tract.

How Much Do We Know?

• Very little research has been done in people on the health effects of acai products.

What Have We Learned?

• There’s no definitive scientific evidence based on studies in people to support the use of acai for any health-related purpose.
• No independent studies have been published in peer-reviewed journals that substantiate claims that acai alone promotes rapid weight loss. Researchers who investigated the safety profile of an acai-fortified juice in rats observed that there were no body weight changes in animals given the juice compared with animals that didn’t receive it.
• A preliminary study suggested that eating acai fruit pulp might reduce blood sugar and cholesterol levels in overweight people.
• Laboratory studies have focused on acai’s potential antioxidant properties, and a juice blend with acai as the main ingredient has been shown to have an antioxidant effect in people. (Antioxidants are substances that may protect cells against certain types of damage.)

What Do We Know About Safety?

• Acai pulp appears to be safe when consumed in the amounts commonly used in foods; however, drinking unprocessed acai juice has been linked to an illness called American trypanosomiasis (also known as Chagas disease).
• Consuming acai might affect MRI test results. If you use acai products and are scheduled for an MRI, check with your health care provider.
• Little is known about whether it’s safe to use acai during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health-talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: aloe

Latin Names: Aloe vera, Aloe africana, Aloe arborescens, Aloe barbadensis

Background

• Aloe is a cactus-like plant that grows in hot, dry climates. It is cultivated in subtropical regions around the world, including the southern border areas of Texas, New Mexico, Arizona, and California.
• Historically, aloe has been used for skin conditions and was thought to improve baldness and promote wound healing.
• Aloe is used topically (applied to the skin) and orally. Topical use of aloe is promoted for acne, lichen planus (a very itchy rash on the skin or in the mouth), oral submucous fibrosis, burning mouth syndrome, burns, and radiation-induced skin toxicity. Oral use of aloe is promoted for weight loss, diabetes, hepatitis, and inflammatory bowel disease (a group of conditions caused by gut inflammation that includes Crohn’s disease and ulcerative colitis).
• In 2002, the U.S. Food and Drug Administration issued a ruling that required manufacturers to remove aloe from over-the-counter laxative products because of a lack of safety data.

How Much Do We Know?

• A number of studies have investigated the usefulness of aloe as a dietary supplement or a topical product for health purposes in people.

What Have We Learned?

• Clinical research suggests that topical application of an aloe-based gel twice daily (along with medical soap and tretinoin gel) may improve acne.
• Clinical research suggests topical application of aloe gel may speed burn healing. There also is evidence that treatment with aloe vera may reduce pain from burns.
• Research suggests topical use of aloe also may help people with herpes simplex, lichen planus, or psoriasis.
• Three trials (with a total of 236 adult participants) have evaluated the use of oral doses of aloe vera for symptoms of irritable bowel syndrome. Results from one trial showed a benefit; the other two trials showed no benefit of aloe vera over placebo.
• In a small European study, 44 adults with ulcerative colitis were randomly assigned to receive aloe vera gel or a placebo twice daily for a month. Almost half of the people treated with aloe vera responded to the treatment whereas 14 percent of those treated with placebo responded.
• Aloe vera has been studied in clinical (human) trials for diabetic foot ulcers and dental plaque, but there’s not enough scientific evidence to show whether aloe vera is helpful for these conditions. A 2009 review article examined data from a mix of laboratory, animal, and clinical trials and concluded that more research is necessary to explore aloe’s clinical effectiveness for a number of different skin conditions.

What Do We Know About Safety?

• Topical use of aloe gel is generally well tolerated. However, there have been occasional reports of burning, itching, and eczema with topical use of aloe gel. Oral use of aloe latex can cause abdominal pain and cramps. Oral consumption of aloe leaf extracts (for as little as 3 weeks and as long as 5 years) has been related to cases of acute hepatitis.
• Animal studies have noted an association between aloe vera leaf extract taken orally and gastrointestinal cancer in rats and mice; however, concerns were expressed about the differences in the product used in that study and those commonly used by consumers. Thus, more research is needed to assess the relevance to human health.
• Overuse of aloe latex may increase the risk of adverse effects from the drug digoxin, used for some heart problems.
• Aloe—both in gel and latex form—when taken by mouth may be unsafe during pregnancy and while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: ashwagandha, Indian ginseng

Latin Names: Withania somnifera

Background

• Ashwagandha is an evergreen shrub found in parts of India, Africa, and the Middle East. It contains several bioactive compounds, including a group of substances known as withanolides. Withanolides have been associated with anti-inflammatory and antioxidant effects.
• Ashwagandha has been in use as a medicinal plant for thousands of years, especially in traditional Ayurvedic medicine.
• Currently, ashwagandha supplements are often promoted for stress and anxiety, sleep, male infertility, and athletic performance. These supplements typically contain ashwagandha root, leaf, or root/leaf extracts.
• Ashwagandha has also been promoted for COVID-19, but there is not sufficient high-quality evidence to support its use.

How Much Do We Know?

• Many clinical trials (studies in people) have looked at the use of ashwagandha for a variety of health conditions. However, many of the studies have had small sample sizes and have used a variety of ashwagandha preparations.

What Have We Learned?

• Research shows that some ashwagandha preparations may be effective for insomnia and stress. However, evidence is unclear about its effects on anxiety.
• There is some limited evidence that suggests that taking ashwagandha for 2 to 4 months may increase testosterone levels and sperm quality.
• There isn’t enough evidence to determine if ashwagandha is helpful for any other health conditions, such as asthma, athletic performance, cognitive function, diabetes, menopause, and female infertility.
• There is not enough high-quality evidence suggesting that ashwagandha is helpful in treating COVID-19.

What Do We Know About Safety?

• Ashwagandha may be safe when taken in the short term (up to 3 months). There is not enough information to allow conclusions about its long-term safety to be reached.
• In some individuals, ashwagandha preparations may cause drowsiness, stomach upset, diarrhea, and vomiting.
• Although it is rare, there have been a number of cases that link liver injury to ashwagandha supplements.
• Ashwagandha should be avoided during pregnancy and should not be used while breastfeeding.
• Ashwagandha is not recommended for people who are about to have surgery, or for those who have autoimmune or thyroid disorders.
• There is evidence that ashwagandha might interact with some medications, including those for diabetes and high blood pressure, medicines that decrease the immune system response (immunosuppressants), sedatives, anti-seizure medications (anticonvulsants), and thyroid hormone medications.
• Because ashwagandha may increase testosterone levels, people with hormone-sensitive prostate cancer should avoid its use. 

Keep In Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.
• Federal Regulation of Herbal Products
  • Depending on what’s in them, how they’re intended to be used, and how they’re administered (orally or topically), herbal products are regulated in a variety of ways. Many herbal products intended for oral use are marketed as dietary supplements. The rules for making and distributing dietary supplements are less strict than those for drugs.
  • Unlike drugs, dietary supplements are not approved by the U.S. Food and Drug Administration (FDA) before they are sold to the public. When public health concerns arise about the safety of a dietary supplement or an ingredient including an herb, the FDA can take action to protect the public. Manufacturers and distributors of supplements are responsible for evaluating the safety and labeling of their products before marketing to ensure that they meet all regulatory requirements. 

Common Names: Asian ginseng, Chinese ginseng, Korean ginseng, red ginseng, white ginseng

Latin Names: Panax ginseng

Background

• Asian ginseng is native to the Far East, including China, Korea, and far-eastern Siberia. It has been used for health-related purposes in traditional Chinese medicine for thousands of years.
• Asian ginseng is one of several types of ginseng. The terms red ginseng and white ginseng refer to Asian ginseng roots prepared in two different ways.
• The part of the plant most frequently used for health purposes is the root.
• Asian ginseng taken orally is promoted for increasing resistance to environmental stress and as a general tonic to improve well-being. Asian ginseng is also promoted as a dietary supplement for a variety of other reasons—to improve physical stamina, concentration, and memory; stimulate immune function; slow the aging process; and relieve various other health problems, such as respiratory and cardiovascular disorders, depression, anxiety, and menopausal hot flashes. Topical use (applied to the skin) of Asian ginseng as part of a multi-ingredient preparation is promoted for premature ejaculation.
• Asian ginseng contains many substances; those thought to be most important are called ginsenosides (or panaxosides).

How Much Do We Know?

• Many of the published randomized controlled trials on Asian ginseng may not be high-quality studies. Therefore, our understanding of Asian ginseng’s health effects is limited.

What Have We Learned?

• Results from a 2013 review of 65 randomized controlled trials suggest that Asian ginseng may help improve glucose metabolism and lower blood sugar. However, the scientists who published the review noted some issues with the studies they examined: that many were not high quality and that ginseng preparations were diverse.

What Do We Know About Safety?

• Short-term oral use (up to 6 months) of Asian ginseng in recommended amounts appears to be safe for most people. However, questions have been raised about its long-term safety, and some experts recommend against its use by infants, children, and women who are pregnant or breastfeeding.
• When used short-term as part of a specific multi-ingredient topical skin application, Asian ginseng is likely safe. Safety after prolonged repetitive topical use has not been determined.
• Insomnia (trouble sleeping) is the herb’s most common side effect. Others include menstrual problems, breast pain, increased heart rate, high or low blood pressure, headache, loss of appetite, and digestive problems.
• Some evidence suggests that Asian ginseng might affect blood sugar. If you have diabetes, consult your health care provider before using Asian ginseng.
• There are uncertainties about whether ginseng might interact with certain medications, such as calcium channel blockers and other high blood pressure medications, as well as statin medications and some antidepressants. Studies on the effect of Asian ginseng on the anticoagulant (blood thinner) warfarin (Coumadin) have had mixed results. If you’re taking medication, consult your health care provider before using Asian ginseng.
• Asian ginseng may be unsafe when taken orally during pregnancy. One of the chemicals in it has been found to cause birth defects in animals. Little is known about whether it’s safe to use Asian ginseng while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: astragale, astragale à feuilles de réglisse, beg kei, milk vetch

Latin Names: Astragalus membranaceus

Background

• Astragalus has been used for centuries in traditional Chinese medicine in combination with other herbs.
• Its root is used for health care purposes.
• Commonly combined with other herbs, astragalus has been promoted as a dietary supplement for many conditions, including upper respiratory infections, allergic rhinitis (hay fever), asthma, chronic fatigue syndrome, and chronic kidney disease, among others. It’s also promoted to strengthen and regulate the immune system. Topical use (application to the skin) of astragalus is promoted for improving blood flow and speeding wound healing.

How Much Do We Know?

• There are no high-quality studies in people of astragalus for any health condition.

What Have We Learned?

• Patients with nephrotic syndrome (health problems related to kidney damage) are susceptible to infections. A 2013 research review found that taking astragalus may be associated with a lower risk of upper respiratory tract infections in children with nephrotic syndrome than prednisone treatment alone. However, the review concluded the studies were of low quality.
• An astragalus-based herbal formula didn’t extend the lives of people with advanced lung cancer, a small 2009 trial reported. The study (with 24 people) was supported in part by the National Center for Complementary and Integrative Health (NCCIH).

What Do We Know About Safety?

• Astragalus may be safe when used orally and appropriately. (Doses up to 60 grams daily for up to 4 months have been used without reported adverse effects.) Some possible side effects with oral use include rash, itching, nasal symptoms, or stomach discomfort, but these are uncommon.
• Astragalus may interact with medications that suppress the immune system.
• Some astragalus species, usually not found in dietary supplements, can be toxic to livestock. Several species that grow in the United States contain the neurotoxin swainsonine and have caused “locoweed” poisoning in animals. Other species contain potentially toxic levels of selenium. Too much selenium can lead to diarrhea, irritability, nausea, skin rashes, and nervous system problems.
• Little is known about whether it’s safe to use astragalus during pregnancy or while breastfeeding. Some research in animals suggests that astragalus can be toxic to the mother and fetus.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: bilberry, European blueberry, whortleberry, huckleberry

Latin Names: Vaccinium myrtillus

Background

• The bilberry bush is native to northern areas of Europe and Asia, the northern United States, and Canada. Its dark berries resemble blueberries.
• Its name is derived from the Danish word bollebar, which means “dark berry.”
• Bilberry has been used for medicinal purposes since the Middle Ages. The berries and leaves are the parts of the plant that are used. Historically, bilberry has been used for a variety of conditions, including diarrhea, inflammation of the mouth, urinary problems, and diabetes. It’s also been used traditionally to prevent scurvy, due to its high vitamin C content. During World War II, British pilots ate bilberry jam, thinking it would improve their night vision.
• Today, bilberry is promoted as a dietary supplement for night vision, cataracts, varicose veins, and other conditions such as atherosclerosis (in which plaque builds up in arteries).

How Much Do We Know?

• We have very few high-quality clinical trials (studies in people) of bilberry supplements.

What Have We Learned?

• There’s little scientific evidence to support the use of bilberry for many health conditions.
• A few recent studies have suggested possible beneficial effects of bilberry. However, these studies involved small numbers of people. More research would be needed to confirm these findings.
  • Results from a small clinical study (24 people) suggest that consuming bilberries may reduce gum inflammation and bleeding.
  • Data from a Japanese study with 88 office workers suggest that a bilberry extract helped with eye fatigue.
  • Data from a small study with 21 people suggest that consuming bilberry juice for 5 days before and 2 days after a half-marathon may lead to small to moderate transient increases in muscle soreness and inflammation in recreationally trained runners.
• The berries have a high concentration of polyphenols called anthocyanins, which some studies suggest may have health benefits.

What Do We Know About Safety?

• Bilberry fruit is considered safe when consumed in amounts typically found in foods, or as an extract for 6 months to a year.
• Bilberry leaves may be unsafe when taken orally (by mouth) in high doses or for long periods of time.
• Little is known about whether it’s safe to use bilberry during pregnancy or while breastfeeding. (Consuming amounts typically found in foods is considered safe.)
• Bilberry may interact with a cancer drug called erlotinib (Tarceval), antidiabetes drugs, or medications that slow blood clotting. If you’re taking medicine, talk with your health care provider before taking bilberry supplements.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: bitter orange, Seville orange, sour orange, zhi shi

Latin Names: Citrus aurantium

Background

• Native to eastern Africa, the Arabian Peninsula, Syria, and Southeast Asia, bitter orange now is grown throughout the Mediterranean region and elsewhere, including California and Florida.
• Bitter orange has been used in traditional Chinese medicine for indigestion, nausea, and constipation.
• Today, various bitter orange products are promoted for heartburn, nasal congestion, weight loss, appetite stimulation or suppression, and athletic performance. Bitter orange is also applied to the skin for pain, bruises, fungal infections, and bedsores. Bitter orange is used in cooking and for adding flavor to beer and spirits.
• The fruit of bitter orange contains p-synephrine and other naturally occurring chemicals. p-Synephrine is structurally similar to ephedrine, the main component in the herb ephedra, but p-synephrine has different pharmacologic properties (how the component acts). The U.S. Food and Drug Administration banned the use of ephedra in dietary supplements because it raises blood pressure and is linked to heart attack and stroke. Bitter orange is commonly used as a substitute for ephedra in dietary supplements.
• The National Collegiate Athletic Association (NCAA) has placed “synephrine (bitter orange)” on its current list of banned drugs, listing it as a stimulant.

How Much Do We Know?

• A small number of studies have investigated the usefulness of bitter orange for health purposes in people.

What Have We Learned?

• Applying bitter orange oil to the skin may help with ringworm, jock itch, and athlete’s foot infections.
• There’s not enough scientific evidence to show whether bitter orange is helpful for other health purposes, such as weight loss, anxiety, and premenstrual syndrome.

What Do We Know About Safety?

• Bitter orange is likely safe when used orally in amounts commonly found in foods.
• There is one case report of a woman having a faster-than-normal heart rate at rest after taking a dietary supplement that contained only bitter orange. There are other case reports of healthy people experiencing fainting, angina, heart attack, and stroke after taking bitter orange as part of multicomponent products. However, because these products contained multiple ingredients, it is difficult to know the role that bitter orange played.
• Evidence regarding the effects of bitter orange (alone or combined with other substances, such as caffeine and green tea) on the heart and cardiovascular system is inconclusive. Some studies showed that bitter orange raised blood pressure and heart rate, but other studies showed that bitter orange didn’t have this effect at commonly used doses.
• Some sources list bitter orange as a stimulant whereas other sources say that it’s not a stimulant at commonly used doses.
• Little is known about whether it’s safe to use bitter orange during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: black cohosh, black snakeroot, macrotys, bugbane, bugwort, rattleroot, rattleweed

Latin Names: Actaea racemosa, Cimicifuga racemosa

Background

• Black cohosh, a member of the buttercup family, grows in North America. Native Americans traditionally used black cohosh for a variety of ailments and introduced it to European colonists.
• Currently, black cohosh is promoted as a dietary supplement for hot flashes and other menopausal symptoms. It’s also been promoted for other conditions, including menstrual cramps and premenstrual syndrome, and to induce labor.
• The part of the black cohosh plant used in herbal preparations is the root or rhizome (underground stem).

How Much Do We Know?

• Black cohosh has been studied for menopause symptoms in people. Most of the older studies were not of the highest quality. More recent studies have been of higher quality, but they have differed in the formulation, plant species, or dose used, so it’s difficult to know the herb’s effects with any certainty. Black cohosh has not been studied as much for conditions other than menopause.

What Have We Learned?

• Research suggests that certain black cohosh extracts and some combination products containing black cohosh may reduce some menopause symptoms. Most of the research has been on a single extract called Remifemin. Research on other black cohosh products has had inconsistent results. Guidelines released in 2015 indicate that there is a lack of consistent evidence for any benefit from black cohosh for menopause symptoms. But a 2017 review of recent research suggests that black cohosh extracts approved for treatment in Europe seem to decrease menopause symptoms.
• The research is inconsistent on whether black cohosh helps to reduce hot flashes that are related to breast cancer treatment. People with breast cancer should avoid using black cohosh before talking with their health care provider.
• There aren’t enough reliable data to show whether black cohosh is effective for other uses.

What Do We Know About Safety?

• In clinical trials, people have taken black cohosh for as long as 12 months with no serious harmful effects.
• Black cohosh can cause some mild side effects, such as stomach upset, cramping, headache, rash, a feeling of heaviness, vaginal spotting or bleeding, and weight gain.
• Some commercial black cohosh products have been found to contain the wrong herb or to contain mixtures of black cohosh and other herbs that are not listed on the label.
• Cases of liver damage—some very serious—have been reported in people taking commercial black cohosh products. These problems are rare, and it is uncertain whether black cohosh was responsible for them. Nevertheless, people with liver disorders should consult a health care provider before taking black cohosh products, and anyone who develops symptoms of liver trouble, such as abdominal swelling, dark urine, or jaundice, while taking black cohosh should stop using it and consult a health care provider.
• The risk of interactions between black cohosh and medicines appears to be small. Preliminary animal research supported by NCCIH and other laboratory research suggested that black cohosh might affect statin medicines, which are used to reduce blood cholesterol levels.
• It’s not clear if black cohosh is safe for women who have had hormone-sensitive conditions such as breast cancer.
• Little is known about whether it’s safe to use black cohosh during pregnancy or while breastfeeding.
• Black cohosh should not be confused with blue cohosh (Caulophyllum thalictroides), which has different effects and may not be safe. Black cohosh has sometimes been used with blue cohosh to stimulate labor, but this use was linked to severe adverse effects in at least one newborn.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: bromelain, pineapple enzyme, pineapple extract

Latin Names: (pineapple plant) Ananas comosus

Background

• Bromelain is a group of enzymes found in the fruit and stem of the pineapple plant. Pineapple is native to the Americas but is now grown throughout the world in tropical and subtropical regions. Historically, natives of Central and South America used pineapple for a variety of ailments, such as digestive disorders.
• Bromelain is promoted as a dietary supplement for reducing pain and swelling, especially of the nose and sinuses, gums, and other body parts after surgery or injury. It is also promoted for osteoarthritis, cancer, digestive problems, and muscle soreness. Topical bromelain is promoted for burns.

How Much Do We Know?

• There have been several studies on the use of bromelain for nasal swelling and inflammation and for removing dead skin from burns. Little research has been done on other uses of bromelain.

What Have We Learned?

• There is not enough high-quality research to say whether bromelain should be recommended for sinusitis.
• Preliminary research has shown that bromelain helps to remove dead and damaged skin from burns in children and adults. Whether bromelain treatment is better than standard treatment for scarring over the long term still needs to be examined.
• There are conflicting research results on whether bromelain, alone or in combination with other ingredients, is helpful for osteoarthritis or for muscle soreness and injury after exercise.
• There are also conflicting research results on whether bromelain is helpful for pain, swelling, and jaw range of motion after wisdom tooth surgery.
• There is not enough research to determine if bromelain is effective for the other conditions for which it has been used, including digestive problems.

What Do We Know About Safety?

• Few side effects of bromelain have been reported in studies. The most commonly reported side effects have been stomach upset and diarrhea.
• Allergic reactions may occur in individuals who are sensitive or allergic to pineapples or who have other allergies.
• Little is known about whether it’s safe to use bromelain during pregnancy or while breastfeeding.
• Bromelain may interact with some medicines, such as the antibiotic amoxicillin. If you take medicines, talk to your health care provider before taking bromelain.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: butterbur, petasites, purple butterbur

Latin Names: Petasites hybridus (also known as Petasites officinalis or Tussilago hybrida)

Background

• Butterbur is a shrub that grows in Europe and parts of Asia and North America. The name, butterbur, is attributed to the traditional use of its large leaves to wrap butter in warm weather.
• In the Middle Ages butterbur was used for plague and fever, and in the 17th century it was used to treat cough, asthma, and skin wounds. More recently, it has been promoted as a dietary supplement for urinary tract symptoms, stomach upset, headaches including migraines, allergic rhinitis (hay fever), and other conditions.

How Much Do We Know?

• There have been a few studies of butterbur for migraines and allergic rhinitis (hay fever) in people, so we have some knowledge of its effects on these two conditions.

What Have We Learned?

• Butterbur appears to help reduce the frequency of migraines in adults and children. In 2012, the American Academy of Neurology recommended its use for preventing migraines. However, the Academy stopped recommending it in 2015 because of serious concerns about possible liver toxicity.
• Some studies of butterbur root or leaf extracts suggest that they may be helpful for symptoms of hay fever (allergic rhinitis), but the data are not convincing.
• One study suggested that a combination product containing butterbur might improve anxiety and depression in people with somatoform disorders. (Somatoform disorders are characterized by physical complaints for which no physiological explanation is found and for which psychological factors are likely involved.)
• Butterbur has not been proven helpful for allergic skin reactions, chronic obstructive bronchitis, insomnia, upset stomach, urinary tract symptoms, asthma, and other conditions.

What Do We Know About Safety?

• Some butterbur products contain chemicals called pyrrolizidine alkaloids (PAs). PAs can damage the liver, lungs, and blood circulation, and possibly cause cancer. Only butterbur products that have been processed to remove PAs and are labeled or certified as PA-free should be considered for use.
• Some countries have withdrawn butterbur products from the market because of concerns about liver toxicity.
• Some experts recommend that butterbur not be used for treating migraine because of its safety concerns.
• Not enough is known about whether it’s safe to apply butterbur products to the skin.
• Several studies, including a few studies of children and adolescents, have reported that PA-free butterbur products seem to be safe when taken by mouth in recommended doses for up to 16 weeks. However, some products claiming to be PA-free may not in fact be. For example, Petadolex is marketed as a PA-free butterbur product, but it has been associated with liver damage in some people, suggesting that it may have had PAs. Also, the safety of longer-term use of butterbur has not been established.
• Butterbur products with PAs should not be used during pregnancy or while breastfeeding because they may cause birth defects or liver damage. Little is known about whether it’s safe to use PA-free butterbur during pregnancy or while breastfeeding.
• PA-free butterbur is generally well tolerated but can cause side effects such as belching, headache, itchy eyes, diarrhea, breathing difficulties, fatigue, upset stomach, and drowsiness.
• Butterbur may cause allergic reactions in people who are sensitive to plants such as ragweed, chrysanthemums, marigolds, and daisies.
• If you’re planning to use butterbur or to give it to your child, tell your (or the child’s) health care provider. Health care providers may consider liver function monitoring for people using butterbur.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: cat’s claw, uña de gato

Latin Names: Uncaria tomentosa, Uncaria guianensis

Background

• Cat’s claw is a woody vine that grows wild in the Amazon rainforest and other tropical areas of Central and South America. Its thorns resemble a cat’s claws.
• The two most common species are U. tomentosa and U. guianensis. Most commercial preparations of cat’s claw contain U. tomentosa.
• Use of cat’s claw dates back 2,000 years. Indigenous people of South and Central America used it to ward off disease.
• Today, cat’s claw is promoted as a dietary supplement for a variety of health conditions, including viral infections (such as herpes, human papilloma virus, and HIV), Alzheimer’s disease, cancer, arthritis, diverticulitis, peptic ulcers, colitis, gastritis, hemorrhoids, parasites, and leaky bowel syndrome.

How Much Do We Know?

• There have been very few high-quality clinical trials (studies done in people) of cat’s claw.

What Have We Learned?

• There’s no conclusive scientific evidence based on studies in people that supports using cat’s claw for any health purpose.

What Do We Know About Safety?

• Cat’s claw appears to be safe when used orally for short periods of time. However, it can cause headache, dizziness, and vomiting in some people.
• Cat’s claw might make the immune system more active, which could increase symptoms of autoimmune diseases. If you have an autoimmune disease, consult your health care provider before using cat’s claw.
• Little is known about whether it’s safe to use cat’s claw during pregnancy or while breastfeeding.
• Cat’s claw may interact with some medications, including some HIV drugs called protease inhibitors. If you take medication, talk with your health care provider before using cat’s claw.
• Cat’s claw may lower blood pressure and slow blood clotting. Talk to your health care provider if either of these effects might be a concern for you.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: chamomile, German chamomile

Latin Names: Matricaria recutita, Chamomilla recutita

Background

• There are two types of chamomile: German chamomile and Roman chamomile. This fact sheet focuses on German chamomile.
• Chamomile was described in ancient medical writings and was an important medicinal herb in ancient Egypt, Greece, and Rome.
• Today, chamomile is promoted for sleeplessness, anxiety, and gastrointestinal conditions such as upset stomach, gas, and diarrhea. It is also used topically for skin conditions and for mouth sores resulting from cancer treatment.

How Much Do We Know?

• Not much is known about the health effects of chamomile because there are few studies on chamomile in people for individual conditions. Also, some studies look at products made of chamomile plus other herbs, so it is difficult to know chamomile’s role from those studies.

What Have We Learned?

• Some preliminary studies suggest that a chamomile dietary supplement might be helpful for generalized anxiety disorder.
• Some research has found that products containing certain combinations of herbs that include chamomile may be of benefit for upset stomach, for diarrhea in children, and for infants with colic. But chamomile alone has not been shown to be helpful for these conditions.
• There’s very little information on chamomile’s effect on insomnia. A 2019 review of six small studies included only one study on insomnia. That one study found that chamomile had no benefit for insomnia. The same 2019 review looked at five studies on chamomile’s effect in non-insomnia populations. The review concluded that chamomile might help improve the individual component of sleep quality over a 4-week period in people without insomnia.

What Do We Know About Safety?

• Chamomile is likely safe when used in amounts commonly found in teas. It might be safe when used orally for medicinal purposes over the short term. The long-term safety of using chamomile on the skin for medicinal purposes is unknown.
• Side effects are uncommon and may include nausea, dizziness, and allergic reactions. Rare cases of anaphylaxis (a life-threatening allergic reaction) have occurred in people who consumed or came into contact with chamomile products.
• People are more likely to experience allergic reactions to chamomile if they’re allergic to related plants such as ragweed, chrysanthemums, marigolds, or daisies.
• Interactions between chamomile and cyclosporine (a drug used to prevent rejection of organ transplants) and warfarin (a blood thinner) have been reported, and there are theoretical reasons to suspect that chamomile might interact with other drugs as well. Talk to your health care provider before taking chamomile if you’re taking any type of medicine.
• Little is known about whether it’s safe to use chamomile during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: chasteberry, chaste tree, vitex, monk's pepper

Latin Names: Vitex agnus-castus

Background

• The chasteberry plant, also called chaste tree, is native to the Mediterranean region and Asia.
• The name “chasteberry” may reflect the traditional belief that the plant promoted chastity. Monks in the Middle Ages reportedly used it to decrease sexual desire. In the past, chasteberry extracts were used to treat a variety of gynecological disorders and skin conditions.
• Today, chasteberry is promoted as a dietary supplement for symptoms of premenstrual syndrome, breast pain associated with the menstrual cycle, infertility, and other conditions.

How Much Do We Know?

• There’s not a lot of strong research on the effectiveness of chasteberry for any condition. We do have some clear safety information on the herb.

What Have We Learned?

• Preliminary studies suggest that chasteberry might be helpful for symptoms of premenstrual syndrome and for breast pain related to the menstrual cycle, but the evidence is not conclusive.
• Researchers have studied chasteberry for infertility in women, but there isn’t enough reliable evidence to know if it helps.

What Do We Know About Safety?

• When used in limited amounts, chasteberry appears to be generally well tolerated. Side effects are generally mild, and may include nausea, headache, gastrointestinal disturbances, or itching.
• Taking chasteberry during pregnancy or while breastfeeding may not be safe.
• It may not be safe for women with hormone-sensitive conditions, such as breast, uterine, or ovarian cancer, to take this herb. It’s possible that chasteberry might interact with some medicines, such as birth control pills, drugs used to treat Parkinson’s disease, and drugs used to treat psychosis. If you’re taking medicine, talk with your health care provider before using chasteberry.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: cinnamon, cinnamon bark, Ceylon cinnamon, cassia cinnamon

Latin Names: Cinnamomum verum (also known as Cinnamomum zeylanicum), Cinnamomum aromaticum (also known as Cinnamomum cassia)

Background

• There are many types of cinnamon. Ceylon cinnamon (Cinnamomum verum), grown primarily in Sri Lanka, is known as “true” cinnamon. Cassia cinnamon (Cinnamomum aromaticum), grown in southeastern Asia, is the most common type sold in North America.
• Used as a spice for thousands of years, cinnamon comes from the bark of various species of cinnamon trees. The leaves, flowers, fruits, and roots of cinnamon trees have also been used in cooking and for medicinal purposes. There are differences in the chemical composition of cinnamon products produced from different species or parts of cinnamon trees.
• Cinnamon has a long history of use in traditional medicine in various parts of the world, including China, India, and Persia (Iran).
• Today, cinnamon is promoted as a dietary supplement for diabetes or for irritable bowel syndrome or other gastrointestinal problems, as well as other conditions. Cassia cinnamon is promoted for topical use (application to the skin) as an insect repellent.

How Much Do We Know?

• There have been many studies of cinnamon, especially for diabetes. However, the results of the studies are difficult to interpret because it’s often unclear what type of cinnamon and what part of the plant were used.

What Have We Learned?

• Studies done in people don’t clearly support using cinnamon for any health condition.
• A 2019 review of 18 studies of cinnamon supplementation in people with diabetes suggested that cinnamon could reduce blood sugar but didn’t have a significant effect on hemoglobin A1C, which reflects blood sugar levels over a longer period of time. However, it’s unclear whether these findings are meaningful because 10 of the studies didn’t identify the type of cinnamon used, and 8 of the studies were judged to be of low quality for other reasons.
• It’s uncertain whether cinnamon is helpful for weight loss or for controlling blood levels of cholesterol and related lipids. There’s not enough evidence to show whether cinnamon is helpful for irritable bowel syndrome.
• It’s unclear whether cassia cinnamon is effective as an insect repellent.

What Do We Know About Safety?

• Cinnamon supplements appear to be safe when consumed in the amounts commonly used in foods as a spice or flavoring agent. Use in larger amounts or for long periods of time is sometimes associated with side effects, most commonly gastrointestinal problems or allergic reactions.
• Cassia cinnamon contains a chemical called coumarin, which can be harmful to the liver. Some cassia cinnamon products contain high levels of this substance. In most cases, consuming cassia cinnamon doesn’t provide enough coumarin to cause significant problems. However, prolonged use of cassia cinnamon could be an issue for sensitive people, such as those with liver disease.
• Little is known about whether it’s safe to use cassia cinnamon during pregnancy or while breastfeeding. Ceylon cinnamon may be unsafe for use during pregnancy if consumed in amounts greater than those commonly found in foods. Little is known about whether it’s safe to use Ceylon cinnamon during breastfeeding in amounts greater than those commonly found in foods.
• Cinnamon should not be used in place of conventional medical care or to delay seeking care if you have health problems. This is particularly true if you have diabetes.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: cranberry, American cranberry, bearberry

Latin Names: Vaccinium macrocarpon (also known as Oxycoccus macrocarpos), Vaccinium oxycoccos

Background

• Cranberry is an evergreen shrub that grows in wet habitats in the Northeastern and North Central parts of the United States.
• Historically, cranberry fruits or leaves were used for bladder, stomach, and liver disorders, as well as diabetes, wounds, and other conditions.
• Today, cranberry is most commonly promoted for urinary tract infections (UTIs).

How Much Do We Know?

• There have been many studies in people of cranberry for UTIs, but there’s little research on cranberry for other conditions.

What Have We Learned?

• ​​​​In general, studies in people who are at increased risk for UTIs or those who have had recurrent UTIs show that cranberry products decrease the risk of UTIs by about one-third. However, there’s still some uncertainty about the effectiveness of cranberry because some of the research has not been of high quality. Also, studies in certain populations at increased risk of UTIs, such as elderly people in long-term care and pregnant women, have had inconsistent results, and studies in other high-risk populations, such as women undergoing gynecological surgeries or people with multiple sclerosis, have not found cranberry to be beneficial.
• In 2020, the U.S. Food and Drug Administration announced that it would permit manufacturers to claim on product labels that there is “limited” evidence that daily consumption of specified amounts of cranberry dietary supplements may reduce the risk of recurrent UTI in healthy women who have had a UTI. A similar claim may be made for cranberry juice beverages, but the evidence must be described as “limited and inconsistent.”
• Cranberry hasn’t been shown to be effective as a treatment for an existing UTI.
• NCCIH-supported research is looking at the effects of polyphenols from cranberry and other fruits and vegetables on the gut microbiome, to see whether these effects may play a role in the association between consumption of these foods and reduced risk of chronic diseases.

What Do We Know About Safety?

• Cranberry products are generally thought to be safe. However, if consumed in very large amounts, they can cause stomach upset and diarrhea, particularly in young children.
• Little is known about whether it’s safe to use cranberry for health purposes during pregnancy or while breastfeeding.
• There is conflicting evidence about whether cranberry interacts with the anticoagulant (blood thinner) warfarin.
• People who think they have a UTI should see a health care provider for diagnosis and treatment. Don’t use cranberry products in place of proven treatment for a UTI.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: dandelion, lion’s tooth, blowball

Latin Names: Taraxacum officinale

Background

• Dandelion is native to Europe but found throughout temperate regions in the Northern Hemisphere. The leaves, flowers, and root of the plant have traditionally been used in Mexican and other North American medicine.
• Today, dandelion is promoted as a “tonic,” as a diuretic, and for a variety of conditions, including infections and digestive symptoms. As a food, dandelion is used as a salad green and in soups, wine, and teas. The roasted root is used as a coffee substitute.

How Much Do We Know?

• We know very little about dandelion’s health effects. There’s little scientific evidence on this herb.

What Have We Learned?

• There’s no compelling scientific evidence supporting the use of dandelion for any health condition.

What Do We Know About Safety?

• The use of dandelion in the amounts commonly found in food is generally considered safe. Less is known about the safety of taking it in larger amounts. Some people are allergic to dandelion; allergic reactions may be more likely in people who are allergic to related plants such as ragweed, chrysanthemums, marigolds, and daisies.
• Little is known about whether it’s safe to use dandelion in amounts greater than those in foods during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: echinacea, purple coneflower, coneflower, American coneflower

Latin Names: Echinacea purpurea, Echinacea angustifolia, Echinacea pallida

Background

• There are nine known species of echinacea, all of which are native to North America. They were used by Native Americans of the Great Plains region as traditional medicines.
• Echinacea is promoted as a dietary supplement for the common cold and other infections, based on the idea that it might stimulate the immune system to more effectively fight infection. Echinacea preparations have been promoted for topical use (application to the skin) for wounds and skin problems.
• Several species of echinacea, most commonly Echinacea purpurea or Echinacea angustifolia, may be included in dietary supplements.

How Much Do We Know?

• Many studies have been done on echinacea for the common cold and other upper respiratory tract infections. Much less research has been done on the use of echinacea for other health purposes.

What Have We Learned?

• Taking echinacea might slightly reduce your chances of catching a cold. Echinacea has not been shown to shorten the length of a cold.
• There isn’t enough evidence to show whether echinacea is helpful for other health conditions.
• Recent NCCIH-sponsored research suggests that the effect of echinacea on immune cells may depend on the types and amounts of bacteria within the echinacea plants and that the composition of the soil in which the plants are grown can affect this bacterial community. However, these findings come from laboratory studies of isolated cells, not studies in people.

What Do We Know About Safety?

• For most adults, short-term oral (by mouth) use of echinacea is probably safe; the safety of long-term use is uncertain.
• Although some preliminary research has been done on the use of echinacea during pregnancy, the safety of using echinacea during pregnancy or while breastfeeding remains uncertain.
• The most common side effects of echinacea are digestive tract symptoms, such as nausea or stomach pain.
• Some people have allergic reactions to echinacea, which may be severe. Some children participating in a clinical trial of echinacea developed rashes, which may have been caused by an allergic reaction.
• Current evidence indicates that the risk of interactions between echinacea supplements and most medications is low.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: European elder, black elder, elderberry, elder flower, sambucus

Latin Names: Sambucus nigra

Background

• Elderberry is the dark purple berry of the European or black elder tree, which grows in the warmer parts of Europe, North America, Asia, and Northern Africa.
• Elderberry has been used in folk medicine to treat colds and flu.
• Elderberry is promoted as a dietary supplement for colds, flu, and other conditions. It has also been promoted for COVID-19 (the disease caused by the new coronavirus), but there is no good evidence to support its use.

How Much Do We Know?

• A small number of studies in people have evaluated elderberry for flu and other upper respiratory infections. Little research has been done on other uses of elderberry.

What Have We Learned?

• Some preliminary research suggests that elderberry may relieve symptoms of flu or other upper respiratory infections.
• No published research studies have evaluated the use of elderberry for COVID-19. The U.S. Food and Drug Administration and Federal Trade Commission have taken action against companies that marketed products with unsubstantiated claims of effectiveness for COVID-19.
• There’s not enough information to show whether elderberry is helpful for any other health purposes.

What Do We Know About Safety?

• Raw unripe elderberries and other parts of the elder tree, such as the leaves and stem, contain toxic substances (e.g., sambunigrin) that can cause nausea, vomiting, and diarrhea; cooking eliminates this toxin. Large quantities of the toxin may cause serious illness.
• Little is known about whether it’s safe to use elderberry during pregnancy or while breastfeeding.

Keep in Mind

• Don’t rely on elderberry or other dietary supplements for prevention or treatment of COVID-19. They have not been shown to be effective.
• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: ephedra, Chinese ephedra, ma huang

Latin Names: Ephedra sinica

Background

• Ephedra is a low evergreen shrub with small scaly leaves. It has a long history of medicinal use in China and India to treat colds, fever, headaches, coughing, wheezing, and other conditions.
• The U.S. Food and Drug Administration (FDA) banned the sale of dietary supplements containing ephedrine alkaloids (stimulant compounds found in Ephedra sinica and some other plants) in the United States in 2004. Prior to the ban, ephedra was an ingredient in some dietary supplements promoted for weight loss, increased energy, and enhanced athletic performance.

How Much Do We Know?

• Almost no new research on ephedra has been performed in the years since its use in dietary supplements was banned in the United States. Prior to the ban, substantial research had been done on ephedra’s short-term effects on weight loss and its harmful effects.

What Have We Learned?

• Prior to the ban, research showed that dietary supplements containing ephedra/ephedrine (usually in combination with caffeine) had modest short-term effects on weight loss. However, this benefit was considered insufficient to outweigh the serious risks of these supplements. No studies had assessed long-term effects on weight. The evidence regarding athletic performance was insufficient to allow any conclusions to be reached.

What Do We Know About Safety?

• The FDA banned dietary supplements containing ephedrine alkaloids because of their serious safety risks. The supplements were associated with cases of heart attack, seizure, stroke, and sudden death. People with a history of cardiovascular disease, those taking high doses of ephedra, and those taking it in combination with other stimulants such as caffeine would be expected to be at increased risk, but some of the severe events occurred in people with no preexisting medical problems, people taking relatively low doses of ephedra, or people taking ephedra alone.
• Taking ephedra may also cause anxiety, dizziness, dry mouth, headache, irritability, nausea, personality changes, insomnia, and other symptoms.
• Because of ephedra’s serious risks, it is considered unsafe for use during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: European mistletoe

Latin Names: Viscum album

Background

• European mistletoe is a parasitic plant that grows on several types of common trees such as apple, oak, pine, and elm. European mistletoe is different from American mistletoe, the type of mistletoe that grows in the United States and is used as a holiday decoration.
• European mistletoe has been used for centuries in traditional medicine for a variety of conditions, including seizures, headaches, and menopause symptoms. Today, European mistletoe is promoted as a treatment for cancer.
• In Europe, European mistletoe extracts that are given by injection are sold as prescription drugs. European mistletoe may also be taken orally (by mouth) as a dietary supplement. The U.S. Food and Drug Administration has not approved the use of European mistletoe as a treatment for cancer or any other medical condition.

How Much Do We Know?

• Although European mistletoe has been studied for cancer, its effects are not well understood because much of the research has been of poor quality.

What Have We Learned?

• There have been clinical trials of European mistletoe for cancer, mostly in Europe. Although some trials indicated that European mistletoe improved survival or quality of life, almost all of the trials had major weaknesses that raise doubts about their findings. These weaknesses have included small numbers of patients, lack of information about the patients, lack of information about the dose of European mistletoe, and problems with the design of the studies.
• The National Center for Complementary and Integrative Health (NCCIH) and the National Cancer Institute performed a preliminary trial to evaluate the safety of injected European mistletoe extract in combination with a cancer drug in patients with advanced cancer. It showed that patients could tolerate the herb/drug combination.
• European mistletoe is not a proven cancer treatment. It should not be used as a treatment for cancer outside of clinical trials.

What Do We Know About Safety?

• European mistletoe berries and leaves can cause serious harmful effects when taken orally (by mouth).
• European mistletoe is probably unsafe for use during pregnancy. Little is known about whether it’s safe for use while breastfeeding.
• Injected European mistletoe extract may cause soreness and inflammation at the injection site, headache, fever, and chills. A few severe allergic reactions have been reported.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: evening primrose oil, EPO

Latin Names: Oenothera biennis

Background

• Evening primrose is a plant native to North and South America that also grows throughout Europe and parts of Asia. It has yellow flowers that open at sunset and close during the day. The oil from evening primrose seeds contains omega-6 fatty acids, including gamma-linolenic acid (GLA).
• Native Americans made poultices from the evening primrose plant for bruises and wounds and used its stem and leaf juices as topical remedies for skin inflammations. The leaves were taken orally for gastrointestinal complaints and sore throats. In the 17th century, evening primrose oil became a popular folk remedy in Europe, where it was known as “King’s cure-all.”
• Today, evening primrose oil dietary supplements are promoted for atopic dermatitis (a type of eczema), rheumatoid arthritis, premenstrual syndrome (PMS), breast pain, menopause symptoms, and other conditions. Evening primrose oil may also be included in products that are applied to the skin.

How Much Do We Know?

• Many studies in people have evaluated evening primrose oil for atopic dermatitis or breast pain. Smaller numbers of studies have evaluated it for other health conditions.

What Have We Learned?

• There’s not enough evidence to support the use of evening primrose oil for any health condition.
• Evening primrose oil, taken orally (by mouth), has not been shown to be helpful for relieving symptoms of atopic dermatitis.
• Studies of evening primrose oil for breast pain have not found it to be more effective than a placebo (an inactive substance).
• There’s insufficient evidence to show whether evening primrose oil is helpful for other conditions, such as PMS and menopause symptoms.

What Do We Know About Safety?

• Evening primrose oil is probably safe for most adults. Less is known about its safety for children.
• Evening primrose oil may be safe for use during pregnancy and while breastfeeding, but the evidence is not conclusive.
• Evening primrose oil is generally well tolerated. The most common side effects are temporary gastrointestinal symptoms such as abdominal pain, fullness, or nausea.
• Evening primrose oil may increase the effects of the HIV medicine lopinavir. As with all dietary supplements, talk with your health care provider before taking evening primrose oil if you are taking any kind of medicine.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: fenugreek

Latin Names: Trigonella foenum-graecum

Background

• Fenugreek is a clover-like herb native to the Mediterranean region, southern Europe, and western Asia. Its seeds, which smell and taste like maple syrup, have been used in cooking and as medicine. Fenugreek is used as an ingredient in spice blends and a flavoring agent in foods, beverages, and tobacco. Fenugreek extracts are also used in soaps and cosmetics.
• In North Africa, Asia, and southern Europe, fenugreek was traditionally used for diabetes and to increase milk supply in women who were breastfeeding.
• Today, fenugreek is promoted as a dietary supplement for diabetes, menstrual cramps, and other conditions and to stimulate milk production during breastfeeding.

How Much Do We Know?

• We have little high-quality evidence about the effects of fenugreek on health conditions, but we do have a fair amount of information on its potential harmful effects.

What Have We Learned?

• A small number of studies have suggested that fenugreek may help lower blood sugar levels in people with diabetes or prediabetes, but most of these studies were not of high quality.
• It’s uncertain whether fenugreek can increase milk supply in breastfeeding women; studies have had mixed results.
• The evidence on fenugreek for other health conditions is too limited for any conclusions to be reached.
• Research partly funded by NCCIH is examining the effects of fenugreek on the function of adipose (fat) tissue and the composition of the gut microbiota (the microorganisms that live in the digestive tract) in mice.

What Do We Know About Safety?

• Fenugreek is believed to be safe in the amounts commonly found in foods. Its safety in larger doses is uncertain. It should not be used by children as a supplement. Potential side effects of fenugreek include diarrhea, nausea, and other digestive tract symptoms and rarely, dizziness and headaches. Large doses may cause a harmful drop in blood sugar. Fenugreek can cause allergic reactions in some people. Cases of liver toxicity have been reported in people taking fenugreek alone or in combination with other herbs.
• Fenugreek is not safe for use during pregnancy in amounts greater than those found in food; its use has been linked to increased risks of birth defects in both animals and people. Little is known about whether it’s safe to use fenugreek in amounts greater than those found in food while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: feverfew, bachelor’s buttons, featherfew

Latin Names: Tanacetum parthenium, Chrysanthemum parthenium, Matricaria parthenium

Background

• Feverfew is native to parts of western Asia and the Balkans, but it now grows throughout the world.
• Feverfew is promoted for fevers, headaches, and arthritis; topically (applied to the skin), it’s promoted for toothache and as an antiseptic and insecticide. Feverfew has been called “medieval aspirin” or “aspirin of the 18th century.”

How Much Do We Know?

• Some clinical studies have looked into feverfew’s use as a remedy for migraine headache. There’s little or no evidence about feverfew for any other health conditions.

What Have We Learned?

• Some research suggests that feverfew may help prevent migraine headaches, but results have been mixed. Some research suggests it may reduce migraine headache frequency, as well as some symptoms, such as pain, nausea/vomiting, and light sensitivity.
• There’s not enough evidence to know if feverfew is helpful for other conditions.

What Do We Know About Safety?

• No serious side effects have been reported from feverfew use. Side effects can include nausea, digestive problems, and bloating; if the fresh leaves are chewed, sores and irritation of the mouth may occur.
• People who are sensitive to ragweed and related plants may experience allergic reactions to feverfew.
• Do not take feverfew while pregnant because it may affect uterine contractions. Little is known about whether it’s safe to use feverfew while breastfeeding.
• Using feverfew topically may cause skin irritation.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: flaxseed, flax, linseed

Latin Names: Linum usitatissimum

Background

• Flaxseed has had a variety of health and industrial uses. Hippocrates wrote about flaxseed being a laxative; North American pioneers made flaxseed dressings for cuts and burns. Fiber from the plant is made into linen, and oil from its seeds is used in paints, among other products.
• Today, flaxseed and flaxseed oil are promoted for a variety of disorders that include stomach and intestinal complaints, such as constipation, diarrhea, and irritable bowel syndrome (IBS). Flaxseed and flaxseed oil are also promoted for heart and blood vessel disorders (for example, high levels of blood fats such as cholesterol and triglycerides), as well as diabetes and other conditions.

How Much Do We Know?

• A number of studies in people have investigated the health effects of flaxseed and flaxseed oil, particularly how flaxseed may affect heart and blood vessel diseases, type 2 diabetes, and menopausal symptoms.

What Have We Learned?

• Flaxseed contains fiber, which may relieve constipation. However, there’s little research on the effectiveness of flaxseed for this condition.
• Authors of a 2019 review article suggest that flaxseed may be helpful for some people diagnosed with heart and blood vessel diseases. (It is not known whether flaxseed oil might have a similar effect.)
• Research suggests that flaxseed may help with blood sugar levels in some people with type 2 diabetes. (It is not known whether flaxseed oil might have a similar effect.)
• Studies have had conflicting results on whether flaxseed helps with symptoms of menopause.
• NCCIH is funding preliminary research on the potential role of flaxseed in inflammation and its effects on the gut microbiome.

What Do We Know About Safety?

• Don’t eat raw or unripe flaxseeds, which may contain potentially toxic compounds.
• Flaxseed and flaxseed oil supplements seem to be well tolerated in limited amounts. Few side effects have been reported.
• Flaxseed may be unsafe during pregnancy as it may have mild hormonal effects, but there is no reliable research on flaxseed’s effects on pregnancy outcomes. Some research suggests that flaxseed oil taken in the second or third trimester of pregnancy may increase the chance of premature births. Little is known about whether it’s safe to use flaxseed while breastfeeding.
• Flaxseed, like any fiber supplement, should be taken with plenty of water, as it could worsen constipation or, in rare cases, cause an intestinal blockage. Both flaxseed and flaxseed oil can cause diarrhea.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: garlic

Latin Names: Allium sativum

Background

• Garlic is the edible bulb from a plant in the lily family. It was traditionally used for health purposes by people in many parts of the world, including the Egyptians, Greeks, Romans, Chinese, and Japanese.
• Currently, garlic is most commonly promoted as a dietary supplement for conditions related to the heart and blood vessels, including high blood cholesterol and high blood pressure.
• Fresh garlic, garlic powder, and garlic oil are used to flavor foods. Garlic may be used topically (applied to the skin).

How Much Do We Know?

• A great deal of research has been done on garlic, especially on garlic’s effect on high blood lipid levels (hyperlipidemia) and high blood pressure (hypertension).

What Have We Learned?

• While there’s conflicting evidence, the most reliable results suggest that taking garlic supplements may reduce total cholesterol and low-density lipoprotein (LDL) cholesterol levels in people with high levels of these blood lipids. If it does, the effect is small, and it may take more than 8 weeks before noting any improvement. Taking garlic doesn’t appear to improve high-density lipoprotein (HDL) levels or triglycerides (another blood lipid).
• Garlic supplements may be helpful for high blood pressure, but the evidence is limited.
• The most reliable research has found that intake of garlic as a food or supplement is not associated with a reduced risk of developing gastric cancer. However, epidemiologic studies suggest a link between higher intakes of vegetables in the garlic family (which includes onions, shallots, chives, and leeks as well as garlic) and lower risks of certain cancers, particularly gastrointestinal cancers.
• There’s not enough evidence to show whether garlic is helpful for the common cold.

What Do We Know About Safety?

• Garlic is probably safe for most people in the amounts usually eaten in foods.
• Little is known about whether it’s safe to use garlic supplements or apply garlic to the skin during pregnancy or while breastfeeding.
• Side effects include breath and body odor, heartburn, and upset stomach. These side effects can be more noticeable with raw garlic. Some people have allergic reactions to garlic.
• Taking garlic supplements may increase the risk of bleeding. If you take an anticoagulant (blood thinner), such as warfarin (Coumadin), or if you need surgery, tell your health care provider if you’re taking or planning to take garlic supplements.
• Garlic supplements may interfere with the effectiveness of some drugs, including saquinavir, a drug used to treat HIV infection. Garlic supplements may also interact with some dietary herbs and other supplements.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: ginger

Latin Names: Zingiber officinale

Background

• Native to parts of Asia, such as China, Japan, and India, ginger has a leafy stem and yellowish-green flowers. The spice comes from the rhizome (underground stem) of the plant.
• Ginger has been used for medicinal purposes in China for more than 2,500 years, and it has had a prominent role in Chinese, Indian, and Japanese medicine since the 1500s.

How Much Do We Know?

• There have been many studies of the use of ginger for health purposes in people.

What Have We Learned?

• Ginger has been studied for several types of nausea and vomiting. Almost all of these studies tested dietary supplements rather than foods.
  • Research shows that ginger may be helpful for mild nausea and vomiting associated with pregnancy.
  • Most studies of ginger for motion sickness haven’t shown it to be helpful.
  • In general, ginger hasn’t been shown to relieve nausea and vomiting associated with cancer chemotherapy, although it might be helpful if taken in combination with certain types of chemotherapy or certain drugs used to prevent nausea and vomiting.
  • It’s uncertain whether ginger is helpful for postoperative nausea and vomiting.
• A small amount of research suggests that ginger dietary supplements might be helpful for menstrual cramps.
• There’s not enough evidence to show whether ginger supplements are helpful for symptoms of knee osteoarthritis.

What Do We Know About Safety?

• Ginger has been used safely in many research studies where it was taken orally (by mouth) as a dietary supplement. Ginger products may also be safe for topical use (on the skin).
• Ginger can have side effects such as abdominal discomfort, heartburn, diarrhea, and mouth and throat irritation, especially if taken in large doses.
• Some studies of the use of ginger during pregnancy suggest it is safe, but the evidence is not conclusive. If you’re considering using ginger while pregnant, consult your health care provider. Little is known about whether it’s safe to use ginger while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: ginkgo, Ginkgo biloba, fossil tree, maidenhair tree, Japanese silver apricot, baiguo, yinhsing

Latin Names: Ginkgo biloba

Background

• Ginkgo, one of the oldest living tree species in the world, has a long history in traditional Chinese medicine. Members of the royal court were given ginkgo nuts for senility. Other historical uses for ginkgo were for asthma, bronchitis, and kidney and bladder disorders.
• Today, the extract from ginkgo leaves is promoted as a dietary supplement for many conditions, including anxiety, allergies, dementia, eye problems, peripheral artery disease (when buildup of plaque narrows the blood vessels that carry blood to the head, organs, and limbs), tinnitus, and other health problems.

How Much Do We Know?

• There have been a lot of studies on the possible health effects and risks of people using ginkgo.

What Have We Learned?

• There’s no conclusive evidence that ginkgo is helpful for any health condition. Although some studies suggest that ginkgo may help to slightly improve some symptoms of dementia, the findings have been described as unreliable. Also, other studies have had conflicting findings. Ginkgo neither helps prevent dementia or cognitive decline nor prevents Alzheimer’s-related dementia from getting worse—this is according to studies that include the long-term Ginkgo Evaluation of Memory Study, which enrolled more than 3,000 older adults and was funded in part by the National Center for Complementary and Integrative Health (NCCIH).
• For various health conditions, a small amount of evidence suggests a benefit from taking ginkgo, but the overall evidence is not conclusive. These conditions include anxiety, diabetic retinopathy, glaucoma, peripheral artery disease, premenstrual syndrome (PMS), schizophrenia, and vertigo.
• Research seems to suggest that ginkgo doesn’t help with memory enhancement in healthy people, high blood pressure, tinnitus, multiple sclerosis, seasonal affective disorder, or the risk of having a heart attack or stroke.

What Do We Know About Safety?

• For most people, ginkgo leaf extract appears to be safe when taken by mouth in moderate amounts.
• Side effects of ginkgo may include headache, stomach upset, dizziness, palpitations, constipation, and allergic skin reactions. If you have a known bleeding risk, you should be cautious about ginkgo possibly increasing your risk of bleeding.
• In a 2013 research study, rodents given ginkgo leaf extract had an increased risk of developing liver and thyroid cancer at the end of the 2-year tests. Whether these results apply to humans is unclear.
• Ginkgo may interact with some conventional medications, including anticoagulants (blood thinners), research reviews show.
• Ginkgo taken orally may be unsafe during pregnancy. It might cause early labor or extra bleeding during delivery if used near that time. Little is known about whether it’s safe to use ginkgo while breastfeeding.
• Fresh (raw) or roasted ginkgo seeds and the unprocessed ginkgo leaves can contain dangerous amounts of a toxic substance.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: goldenseal, yellow root

Latin Names: Hydrastis canadensis

Background

• Goldenseal is a plant native to North America. Overharvesting and loss of habitat have decreased the availability of wild goldenseal, but the plant is now grown commercially in the United States, especially in the Blue Ridge Mountains.
• Historically, Native Americans used goldenseal for skin disorders, ulcers, fevers, and other conditions. European settlers adopted it as a medicinal plant, using it for a variety of conditions.
• Currently, goldenseal is promoted as a dietary supplement for colds and other respiratory tract infections, allergic rhinitis (hay fever), ulcers, and digestive upsets such as diarrhea and constipation. It is also used as a mouthwash for sore gums and as an eyewash for eye inflammation, and it is applied to the skin for rashes and other skin problems.

How Much Do We Know?

• Very little research has been done on the health effects of goldenseal.

What Have We Learned?

• The scientific evidence does not support the use of goldenseal for any health-related purpose.
• Berberine, a substance found in goldenseal, has been studied for heart failure, diarrhea, infections, and other health conditions. However, when people take goldenseal orally (by mouth), very little berberine may be absorbed by the body or enter the bloodstream, so study results on berberine may not apply to goldenseal.
• The National Center for Complementary and Integrative Health (NCCIH) is funding research to study how goldenseal may interact with medications in people.

What Do We Know About Safety?

• Little information is available on the safety of goldenseal taken alone. Goldenseal might be safe for most adults when taken by mouth in the short term. There is not enough reliable information to know if goldenseal is safe for long-term use.
• Women who are pregnant or breastfeeding should not use goldenseal, and it should not be given to infants. Berberine can cause or worsen jaundice in newborn infants and could lead to a life-threatening problem called kernicterus.
• An NCCIH-funded study found that some commercial goldenseal dietary supplements didn’t contain much goldenseal and instead included ingredients not listed on their labels.
• Goldenseal may change the way your body processes many medications. If you’re taking medication, consult your health care provider before using goldenseal.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: grape seed extract, grape seed

Latin Names: Vitis vinifera

Background

• Grape seed extract, which is made from the seeds of wine grapes, is promoted as a dietary supplement for various conditions, including venous insufficiency (when veins have problems sending blood from the legs back to the heart), promoting wound healing, and reducing inflammation.
• Grape seed extract contains proanthocyanidins, which have been studied for a variety of health conditions.

How Much Do We Know?

• There are some well-controlled studies of people using grape seed extract for certain health conditions. For many health conditions, however, there’s not enough high-quality evidence to rate the effectiveness of grape seed extract.

What Have We Learned?

• Some studies suggest that grape seed extract might help with symptoms of chronic venous insufficiency and with eye stress from glare, but the evidence isn’t strong.
• Conflicting results have come from studies on grape seed extract’s effect on blood pressure. It’s possible that grape seed extract might help to slightly lower blood pressure in healthy people and those with high blood pressure, particularly in people who are obese or have metabolic syndrome. But people with high blood pressure should not take high doses of grape seed extract with vitamin C because the combination might worsen blood pressure.
• A 2019 review of 15 studies involving 825 participants suggested that grape seed extract might help lower levels of LDL cholesterol, total cholesterol, triglycerides, and the inflammatory marker C-reactive protein. The individual studies, however, were small in size, which could affect the interpretation of the results.
• The National Center for Complementary and Integrative Health (NCCIH) is supporting research on how certain dietary supplements rich in polyphenols, including grape seed extract, help to reduce the effects of stress on the body and mind. (Polyphenols are substances that are found in many plants and have antioxidant activity.) This research is also looking at how the microbiome affects the absorption of the specific polyphenol components that are helpful.

What Do We Know About Safety?

• Grape seed extract is generally well tolerated when taken in moderate amounts. It has been tested safely for up to 11 months in human studies. It’s possibly unsafe if you have a bleeding disorder or are going to have surgery or if you take anticoagulants (blood thinners), such as warfarin or aspirin.
• Little is known about whether it’s safe to use grape seed extract during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: green tea

Latin Names: Camellia sinensis

Background

• Green, black, and oolong teas all come from the same plant, Camellia sinensis, but are prepared using different methods. To produce green tea, leaves from the plant are steamed, pan fried, and dried.
• Tea has been used for medicinal purposes in China and Japan for thousands of years.
• Green tea as a beverage or dietary supplement is promoted for improving mental alertness, relieving digestive symptoms and headaches, and promoting weight loss. Green tea and its components, including epigallocatechin-3-gallate (EGCG), have been studied for their possible protective effects against heart disease and cancer.
• The U.S. Food and Drug Administration (FDA) has approved a topical ointment, sinecatechins (brand name Veregen), which includes extracted components of green tea leaves and is used for the treatment of genital warts.

How Much Do We Know?

• Although many studies have been done on green tea and its extracts, definite conclusions cannot yet be reached on whether green tea is helpful for most of the purposes for which it is used.

What Have We Learned?

• Green tea contains caffeine. Drinking caffeinated beverages throughout the day seems to prevent a decline in alertness. One study looked at the effect of taking only a main component of green tea—EGCG—on mental capabilities. In that study, mental capabilities in adults didn’t improve.
• The FDA has approved a specific green tea extract ointment as a prescription drug for treating genital warts.
• Studies of green tea and cancer in people have had inconsistent results. The National Cancer Institute does not recommend for or against using green tea to reduce the risk of any type of cancer.
• A small number of studies suggests that both green and black tea might have beneficial effects on some heart disease risk factors, including blood pressure and cholesterol. The research has limitations though, including how the data was evaluated and differences in study populations, so no definite conclusions have been reached.
• Green tea extracts haven’t been shown to produce a meaningful weight loss in adults who are overweight or obese. They also haven’t been shown to help people maintain a weight loss.
• It’s uncertain whether green tea is helpful for other conditions.
• The National Center for Complementary and Integrative Health (NCCIH) is funding research on green tea and its extracts, including studies on new forms of green tea extracts for preventing symptoms of inflammatory bowel disease and for lowering cholesterol.

What Do We Know About Safety?

• Green tea, when consumed as a beverage, is believed to be safe when used in amounts up to 8 cups per day. Keep in mind that only the amount of added caffeine must be stated on product labels and not the caffeine that naturally occurs in green tea.
• Drinking green tea may be safe during pregnancy and while breastfeeding when consumed in amounts up to 6 cups per day (no more than about 300 mg of caffeine). Drinking more than this amount during pregnancy may be unsafe and may increase the risk of negative effects. Green tea may also increase the risk of birth defects associated with folic acid deficiency. Caffeine passes into breast milk and can affect a breastfeeding infant.
• Although uncommon, liver problems have been reported in a number of people who took green tea products, primarily green tea extracts in pill form. People with liver disease should consult a health care provider before taking products with green tea extract. People taking green tea extracts, especially those with liver disease, should discontinue use and consult a health care provider if they develop symptoms of liver trouble (such as abdominal pain, dark urine, or jaundice).
• Green tea is an ingredient in many over-the-counter weight loss products, some of which have been identified as the likely cause of rare cases of liver injury.
• Green tea at high doses has been shown to reduce blood levels and therefore the effectiveness of the drug nadolol, a beta-blocker used for high blood pressure and heart problems. It may also interact with other medicines.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: hawthorn, English hawthorn, oneseed hawthorn, harthorne, haw, hawthorne

Latin Names: Crataegus monogyna, Crataegus laevigata (synonym Crataegus oxyacantha)

Background

• Hawthorn is a flowering shrub or tree of the rose family. It grows in temperate regions throughout the world.
• Historically, hawthorn has been used for heart disease as well as for digestive and kidney problems. It is now promoted for these uses as well as for anxiety, high or low blood pressure, and other conditions.

How Much Do We Know?

• Hawthorn has been studied for heart failure in people. Heart failure is a condition in which the heart can’t pump as much blood as it should.
• Not much is known about hawthorn for any other health conditions as there is little or no evidence.

What Have We Learned?

• There is conflicting evidence about the effects of hawthorn in people with heart failure. Although some older, short-term studies suggested that hawthorn may have benefits in patients with heart failure, other, more recent, studies did not confirm these benefits. In these studies, unlike some of the older ones, patients were given hawthorn in addition to the recommended conventional treatments for heart failure. One of the studies suggested possible harm in people taking hawthorn as it appears to increase the early risk of heart failure progression.

What Do We Know About Safety?

• In most studies of hawthorn for heart failure, no serious safety problems have been reported. However, in one study, patients taking hawthorn were more likely than those taking a placebo (an inactive substance) to have their heart failure get worse soon after the study started. The reason for this is not clear, but one possibility is that hawthorn might have interacted with drugs the patients were taking.
• Side effects of hawthorn can include dizziness, nausea, and digestive symptoms.
• Hawthorn may interact in harmful ways with drugs, including some heart medications. If you’re taking medication and you’re considering using hawthorn, consult your health care provider.
• Little is known about whether it’s safe to use hawthorn during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: hoodia, Kalahari cactus, Xhoba

Latin Names: Hoodia gordonii

Background

• Hoodia is a cactus-like plant that grows in Africa’s Kalahari Desert. Historically, the San Bushmen are believed to have used hoodia to suppress appetite.
• Today, hoodia dietary supplements are promoted as appetite suppressants for weight loss.

How Much Do We Know?

• We know very little about hoodia because only one study of this herb has been done in people.

What Have We Learned?

• In the one small study of hoodia in people, overweight women who took hoodia for 15 days didn’t lose more weight than those who took a placebo.

What Do We Know About Safety?

• Little is known about the safety of hoodia. However, the one completed study in people raises concerns. In that study, participants taking hoodia had more side effects than those taking placebos, including nausea, vomiting, dizziness, and odd skin sensations. Of concern, hoodia significantly affected some clinical and safety parameters, such as blood pressure, bilirubin, and electrocardiogram (heart function) measures.
• Little is known about whether it’s safe to use hoodia during pregnancy or while breastfeeding.
• Whether hoodia interacts with medicines or other supplements is not known.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: horse chestnut, buckeye, Spanish chestnut

Latin Names: Aesculus hippocastanum

Background

• Horse chestnut is a tree native to parts of southeastern Europe. Its fruits contain seeds that resemble sweet chestnuts but have a bitter taste.
• Historically, horse chestnut seed extract was used for joint pain, bladder and gastrointestinal problems, fever, leg cramps, and other conditions.
• Today, horse chestnut seed extract is promoted for chronic venous insufficiency (CVI; poor blood flow in the veins of the legs, which may lead to leg pain, swelling, itchiness, and other symptoms), irritable bowel syndrome, male infertility, and other conditions.

How Much Do We Know?

• Some studies in people have looked at horse chestnut seed extract for CVI, but very little research has been done on its use for other conditions.

What Have We Learned?

• A 2012 systematic review of 17 studies suggested that horse chestnut seed extract can improve symptoms of CVI. Results from one of these studies suggested that horse chestnut seed extract may be as effective as wearing compression stockings. The reviewers noted, however, that there is a need for more rigorous, large-scale randomized controlled trials to assess the efficacy of this treatment option for CVI.
• Small amounts of research have been done on horse chestnut seed extract for male infertility associated with varicocele (a swelling of veins inside the scrotum) and for irritable bowel syndrome, but there’s not enough information to draw definite conclusions about its effects on either condition.

What Do We Know About Safety?

• The raw seeds, bark, flowers, and leaves of horse chestnut are unsafe because they contain a toxic component. Standardized horse chestnut seed extracts, from which this component has been removed, appear to be safe for short-term use.
• Horse chestnut seed extracts are generally well tolerated but may cause side effects such as dizziness, nausea, and digestive upsets in some people.
• Little is known about whether it’s safe to use horse chestnut seed extract during pregnancy or while breastfeeding. No one—including women who are pregnant or breastfeeding—should consume raw horse chestnut.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: kava, kava kava, ava pepper, ava root, kawa

Latin Names: Piper methysticum

Background

• Kava is native to the islands of the western Pacific and is a member of the pepper family.
• Pacific islanders have used kava for thousands of years as a medicine and for ritual purposes.
• Today, kava is promoted as a dietary supplement for anxiety, insomnia, and other conditions.

How Much Do We Know?

• There has been a fair amount of research in people on the use of kava for anxiety, but few studies have been done on other conditions.

What Have We Learned?

• Kava supplements may have a small effect on reducing anxiety, but they have been linked to a risk of severe liver injury.
• There isn’t enough evidence to show whether kava is helpful for any other conditions.

What Do We Know About Safety?

• The use of kava has been linked to liver injury that is sometimes serious or even fatal. The exact cause and frequency of the liver damage are unclear.
• Kava can cause digestive upset, headache, dizziness, and other side effects. The use of kava may affect the ability to drive or operate machinery. Long-term use of high doses of kava may cause kava dermopathy, a condition that involves dry, scaly, flaky skin with a yellow discoloration.
• Kava may have special risks if taken during pregnancy or while breastfeeding because of the presence of harmful pyrone constituents.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: lavender, English lavender, common lavender, French lavender

Latin Names: Lavandula angustifolia

Background

• Lavender is native to countries in the Mediterranean region, including France, Spain, and Italy.
• The name lavender comes from the Latin verb “lavare,” meaning “to wash.” In ancient Rome, lavender was used as a bath additive.
• Lavender is used to flavor foods and beverages and as a fragrance ingredient in soaps and cosmetics. It is promoted as a dietary supplement for anxiety, depression, digestive symptoms, and other conditions. It is also promoted for topical use (application to the skin) and use in aromatherapy.

How Much Do We Know?

• Studies have been done on the use of lavender for a variety of conditions, but there hasn’t been enough high-quality research to allow definite conclusions to be reached about its effectiveness.

What Have We Learned?

• Studies of a lavender oil product that is taken orally (by mouth) have suggested it might be beneficial for anxiety, but because of limitations of the research, including the small size of the studies, no definite conclusions can be reached about its effectiveness.
• It’s uncertain whether lavender oil used as aromatherapy is helpful for anxiety or other conditions.

What Do We Know About Safety?

• Consumption of lavender in the amounts typically used in foods is likely to be safe. Short-term oral use in the amounts tested in studies of lavender for anxiety or other conditions may also be safe.
• The topical use of products containing lavender may cause allergic skin reactions in some people.
• A few cases of swelling of breast tissue have been reported in children who used topical products containing lavender. However, it’s unclear whether the lavender was responsible for the breast swelling, a condition that can have many causes.
• Little is known about whether it’s safe to use lavender during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: licorice root, licorice, liquorice, sweet root, gan cao, gan zao, Chinese licorice

Latin Names: Glycyrrhiza glabra, Glycyrrhiza uralensis, Glycyrrhiza inflata

Background

• Licorice root is cultivated throughout Europe, Asia, and the Middle East. It is used as a flavoring in candy, other foods, beverages, and tobacco products.
• Many “licorice” products sold in the United States do not contain actual licorice. Anise oil, which smells and tastes like licorice, is often used instead.
• Licorice root has a long history of use, going back to ancient Assyrian, Egyptian, Chinese, and Indian cultures. It was used traditionally for treating a variety of conditions, including lung, liver, circulatory, and kidney diseases.
• Today, licorice root is promoted as a dietary supplement for conditions such as digestive problems, menopausal symptoms, cough, and bacterial and viral infections. Licorice gargles or lozenges have been used to try to prevent or reduce the sore throat that sometimes occurs after surgery. Licorice is also an ingredient in some products for topical use (application to the skin).

How Much Do We Know?

• Some studies of licorice root in people have been completed, but there isn’t enough high-quality evidence to clearly support its use for any health condition.

What Have We Learned?

• Some products that contain licorice root and other ingredients may help relieve digestive symptoms. Because these are combination products, the role of licorice in their effects is uncertain.
• There’s some evidence that topical gels containing licorice root might be helpful for atopic dermatitis symptoms. Atopic dermatitis, also called eczema, is a chronic disease in which skin becomes irritated, inflamed, and itchy.
• A small number of studies suggest that using a licorice gargle or lozenges before surgery might help to prevent or lessen the severity of the sore throat that often occurs after surgery.

What Do We Know About Safety?

• Although licorice root is generally considered safe as a food ingredient, it can cause serious side effects, including increased blood pressure and decreased potassium levels, when consumed in large amounts or for long periods of time. Because the composition of licorice products varies, it isn’t possible to definitely say that a particular level of intake is safe or unsafe. The effects of licorice on potassium and blood pressure are a particular concern for people with hypertension (high blood pressure) or heart or kidney disease.
• Some side effects of licorice are believed to be caused by a component called glycyrrhizic acid. Licorice that has had this substance removed (called DGL for deglycyrrhizinated licorice) may not have the same degree of side effects.
• Heavy consumption of licorice during pregnancy has been associated with premature birth and health problems in the child. Little is known about whether it’s safe to use licorice root while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: milk thistle, Mary thistle, holy thistle

Latin Names: Silybum marianum, synonym Carduus marianus

Background

• Milk thistle is native to Europe and was introduced into North America by early colonists. Milk thistle is found throughout the eastern United States, California, South America, Africa, Australia, and Asia.
• The terms “milk thistle” and “silymarin” are often used interchangeably.
• Historically, people have used milk thistle for liver disorders and gallbladder problems.
• Milk thistle is promoted as a dietary supplement for hepatitis, cirrhosis, jaundice, diabetes, indigestion, and other conditions.

How Much Do We Know?

• We know little about whether milk thistle is effective in people, as only a few well-designed clinical studies have been conducted.

What Have We Learned?

• Results from clinical trials of milk thistle for liver diseases have been conflicting or haven’t been clinically meaningful. Some of the studies have been of poor quality, too.
• Although some studies have shown positive results on milk thistle for people with chronic hepatitis C virus (HCV) infection, the overall research does not show a benefit.
• A small number of studies have suggested that milk thistle extract might be beneficial for diabetes, but the conclusions about its effectiveness are not definite.
• It’s not known whether milk thistle is helpful for other conditions.

What Do We Know About Safety?

• In clinical trials, milk thistle appears to be well tolerated in recommended doses. Occasionally, people report various digestive side effects.
• Milk thistle may produce allergic reactions, which tend to be more common among people who are allergic to plants in the same family (for example, ragweed, chrysanthemum, marigold, and daisy).
• Milk thistle may lower blood sugar levels in people with type 2 diabetes. People with diabetes should use caution.
• Little is known about whether it’s safe to use milk thistle during pregnancy or while breastfeeding.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

Common Names: mugwort, common wormwood, wild wormwood, felon herb, chrysanthemum weed, St. John’s plant, sailor’s tobacco

Latin Names: Artemisia vulgaris

Background

• Mugwort is a perennial plant that is native to Europe and parts of Asia and Africa. It now grows in many parts of the world, including North America.
• Historically, mugwort has been used in traditional systems of medicine in different parts of the world.
• Today, mugwort taken orally (by mouth) is promoted for digestive problems, irregular menstruation, and high blood pressure. It is also promoted as a sedative, laxative, and liver tonic.
• Mugwort lotion applied topically (to the skin) is promoted for itching caused by hypertrophic scars (visible, raised scars that can sometimes cause restricted movement of muscles, joints, and tendons).

How Much Do We Know?

• Very little research has been done on mugwort in people.