Vitamins are substances that your body needs to grow and develop normally. There are 13 vitamins your body needs. They are

• Vitamin A
• B vitamins (thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B-6, vitamin B-12 and folate)
• Vitamin C
• Vitamin D
• Vitamin E
• Vitamin K

You can usually get all your vitamins from the foods you eat. Your body can also make vitamins D and K. People who eat a vegetarian diet may need to take a vitamin B12 supplement.

Each vitamin has specific jobs. If you have low levels of certain vitamins, you may get health problems. For example, if you don't get enough vitamin C, you could become anemic. Some vitamins may help prevent medical problems. Vitamin A prevents night blindness.

The best way to get enough vitamins is to eat a balanced diet with a variety of foods. In some cases, you may need to take vitamin supplements. It's a good idea to ask your health care provider first. High doses of some vitamins can cause problems.

Vitamins are organic compounds found in foods and are a necessary part of the biochemical reactions in the body. They are involved in a number of processes, including mineral and bone metabolism, and cell and tissue growth, and they act as cofactors for energy metabolism. The B vitamins play the largest role of any vitamins in metabolism.

You get most of your vitamins through your diet, although some can be formed from the precursors absorbed during digestion. For example, the body synthesizes vitamin A from the β-carotene in orange vegetables like carrots and sweet potatoes. Vitamins are either fat-soluble or water-soluble. Fat-soluble vitamins A, D, E, and K, are absorbed through the intestinal tract with lipids in chylomicrons. Vitamin D is also synthesized in the skin through exposure to sunlight. Because they are carried in lipids, fat-soluble vitamins can accumulate in the lipids stored in the body. If excess vitamins are retained in the lipid stores in the body, hypervitaminosis can result.

Water-soluble vitamins, including the eight B vitamins and vitamin C, are absorbed with water in the gastrointestinal tract. These vitamins move easily through bodily fluids, which are water based, so they are not stored in the body. Excess water-soluble vitamins are excreted in the urine. Therefore, hypervitaminosis of water-soluble vitamins rarely occurs, except with an excess of vitamin supplements.

Fat-soluble Vitamins

Water-soluble Vitamins

Vitamin A is a nutrient that the body needs in small amounts to function and stay healthy. Vitamin A helps in vision, bone growth, reproduction, growth of epithelium (cells that line the internal and external surfaces of the body), and fighting infections. It is fat-soluble (can dissolve in fats and oils). Vitamin A is found in liver, egg yolks, and whole milk dairy products from animals and in fish oils. It can also be made in the body from a substance found in some fruits and vegetables, such as cantaloupes, carrots, spinach, and sweet potatoes. Vitamin A is being studied in the prevention and treatment of some types of cancer. Also called retinol.

A compound containing several or all of a group of vitamins and nutrients that the body needs in very small amounts to function and stay healthy. The B vitamins in the vitamin B complex include thiamine, riboflavin, niacin (nicotinic acid), niacinamide (nicotinamide), the vitamin B6 group (including pyridoxine, pyridoxal, pyridoxamine), biotin, pantothenic acid, folic acid, and vitamin B12. Aminobenzoic acid, inositol, and choline are sometimes included as part of the vitamin B complex. The vitamin B complex is water-soluble (can dissolve in water) and is found in yeast, seeds, eggs, liver, meat, and vegetables. Members of the vitamin B complex are being studied in the prevention and treatment of some types of cancer.

Vitamin C is a nutrient that the body needs in small amounts to function and stay healthy. Vitamin C helps fight infections, heal wounds, and keep tissues healthy. It is an antioxidant that helps prevent cell damage caused by free radicals (highly reactive chemicals). Vitamin C is found in all fruits and vegetables, especially citrus fruits, strawberries, cantaloupe, green peppers, tomatoes, broccoli, leafy greens, and potatoes. It is water-soluble (can dissolve in water) and must be taken in every day. Vitamin C is being studied in the prevention and treatment of some types of cancer. Also called ascorbic acid.

A nutrient that the body needs in small amounts to function and stay healthy. Vitamin D helps the body use calcium and phosphorus to make strong bones and teeth. It is fat-soluble (can dissolve in fats and oils) and is found in fatty fish, egg yolks, and dairy products. Skin exposed to sunshine can also make vitamin D. Not enough vitamin D can cause a bone disease called rickets. It is being studied in the prevention and treatment of some types of cancer. Also called cholecalciferol.

A nutrient that the body needs in small amounts to stay healthy and work the way it should. It is fat-soluble (can dissolve in fats and oils) and is found in seeds, nuts, leafy green vegetables, and vegetable oils. Vitamin E boosts the immune system and helps keep blood clots from forming. It also helps prevent cell damage caused by free radicals (highly reactive chemicals). Vitamin E is being studied in the prevention and treatment of some types of cancer. It is a type of antioxidant. Also called alpha-tocopherol.

A nutrient that the body needs in small amounts to function and stay healthy. Vitamin K helps to form blood clots (a mass that forms when blood platelets, proteins, and cells stick together) and maintain strong bones. It is fat-soluble (can dissolve in fats and oils) and is found in green leafy vegetables, broccoli, liver, and vegetable oils. Vitamin K is also made by bacteria that live in the large intestine. Not enough vitamin K can lead to bleeding and bruising. It is a type of phylloquinone.

When you reach for that bottle of vitamin C or fish oil pills, you might wonder how well they’ll work and if they’re safe. The first thing to ask yourself is whether you need them in the first place.

More than half of all Americans take one or more dietary supplements daily or on occasion. Supplements are available without a prescription and usually come in pill, powder or liquid form. Common supplements include vitamins, minerals and herbal products, also known as botanicals.

People take these supplements to make sure they get enough essential nutrients and to maintain or improve their health. But not everyone needs to take supplements.

“It’s possible to get all of the nutrients you need by eating a variety of healthy foods, so you don’t have to take one,” says Carol Haggans, a registered dietitian and consultant to NIH. “But supplements can be useful for filling in gaps in your diet.”

Some supplements may have side effects, especially if taken before surgery or with other medicines. Supplements can also cause problems if you have certain health conditions. And the effects of many supplements haven’t been tested in children, pregnant women and other groups. So talk with your health care provider if you’re thinking about taking dietary supplements.

“You should discuss with your doctor what supplements you’re taking so your care can be integrated and managed,” advises Dr. Craig Hopp, an expert in botanicals research at NIH.

Dietary supplements are regulated by the U.S. Food and Drug Administration (FDA) as foods, not as drugs. The label may claim certain health benefits. But unlike medicines, supplements can’t claim to cure, treat or prevent a disease.

“There’s little evidence that any supplement can reverse the course of any chronic disease,” says Hopp. “Don’t take supplements with that expectation.”

Evidence does suggest that some supplements can enhance health in different ways. The most popular nutrient supplements are multivitamins, calcium and vitamins B, C and D. Calcium supports bone health, and vitamin D helps the body absorb calcium. Vitamins C and E are antioxidants—molecules that prevent cell damage and help to maintain health.

Women need iron during pregnancy, and breastfed infants need vitamin D. Folic acid—400 micrograms daily, whether from supplements or fortified food—is important for all women of childbearing age.

Vitamin B12 keeps nerve and blood cells healthy. “Vitamin B12 mostly comes from meat, fish and dairy foods, so vegans may consider taking a supplement to be sure to get enough of it,” Haggans says.

Research suggests that fish oil can promote heart health. Of the supplements not derived from vitamins and minerals, Hopp says, “fish oil probably has the most scientific evidence to support its use.”

The health effects of some other common supplements need more study. These include glucosamine (for joint pain) and herbal supplements such as echinacea (immune health) and flaxseed oil (digestion).

Many supplements have mild effects with few risks. But use caution. Vitamin K, for example, will reduce the ability of blood thinners to work. Ginkgo can increase blood thinning. The herb St. John’s wort is sometimes used to ease depression, anxiety or nerve pain, but it can also speed the breakdown of many drugs—such as antidepressants and birth control pills—and make them less effective.

Just because a supplement is promoted as “natural” doesn’t necessarily mean it’s safe. The herbs comfrey and kava, for example, can seriously damage the liver.

“It’s important to know the chemical makeup, how it’s prepared, and how it works in the body—especially for herbs, but also for nutrients,” says Haggans. “Talk to a health care provider for advice on whether you need a supplement in the first place, the dose and possible interactions with medicine you’re already taking.”

For vitamins and minerals, check the % Daily Value (DV) for each nutrient to make sure you’re not getting too much. “It’s important to consider the DV and upper limit,” says Haggans. Too much of certain supplements can be harmful.

Scientists still have much to learn even about common vitamins. One recent study found unexpected evidence about vitamin E. Earlier research suggested that men who took vitamin E supplements might have a lower risk of developing prostate cancer. “But much to our surprise, a large NIH-funded clinical trial of more than 29,000 men found that taking supplements of vitamin E actually raised—not reduced—their risk of this disease,” says Dr. Paul M. Coates, director of NIH’s Office of Dietary Supplements. That’s why it’s important to conduct clinical studies of supplements to confirm their effects.

Because supplements are regulated as foods, not as drugs, the FDA doesn’t evaluate the quality of supplements or assess their effects on the body. If a product is found to be unsafe after it reaches the market, the FDA can restrict or ban its use.

Manufacturers are also responsible for the product’s purity, and they must accurately list ingredients and their amounts. But there’s no regulatory agency that makes sure that labels match what’s in the bottles. You risk getting less, or sometimes more, of the listed ingredients. All of the ingredients may not even be listed.

A few independent organizations conduct quality tests of supplements and offer seals of approval. This doesn’t guarantee the product works or is safe; it just assures the product was properly made and contains the listed ingredients.

“Products sold nationally in the stores and online where you usually shop should be fine,” Coates says. “According to the FDA, supplement products most likely to be contaminated with pharmaceutical ingredients are herbal remedies promoted for weight loss and for sexual or athletic performance enhancement.”

To make it easy to find reliable information, NIH has fact sheets on dietary supplements at ods.od.nih.gov/factsheets/list-all/. NIH also recently launched an online Dietary Supplement Label Database at www.dsld.nlm.nih.gov. This free database lets you look up the ingredients of thousands of dietary supplements. It includes information from the label on dosage, health claims and cautions.

For more personalized, on-the-go information about dietary supplements, check out NIH’s free updated app for your smart phone or tablet: My Dietary Supplements (MyDS).

The MyDS app provides the latest supplement information and lets you keep track of the vitamins, minerals, herbs and other products you take. You can even keep track of supplements taken by your parents, spouse or children.

“Deciding whether to take dietary supplements and which ones to take is a serious matter,” says Coates. “Learn about their potential benefits and any risks they may pose first. Speak to your health care providers about products of interest and decide together what might be best for you to take, if anything, for your overall health.”

Safe Use of Supplements

• Tell all of your health care providers about any dietary supplements you use. Some supplements can interact with medications or affect medical conditions.
• Read the label instructions for use.
• “Natural” doesn’t always mean safe. For up-to-date news about the safety of particular supplements, check nccam.nih.gov/news/alerts.
• Too much might be harmful. Don’t take more than the recommended dose.

More is better, right? Not when it comes to vitamins and minerals. Our bodies need these nutrients for many things, like breaking down the food we eat, making bones and DNA, helping muscles contract, and maintaining immunity. But there’s no reason to get more than you need, and some nutrients can be dangerous in large amounts.

Each vitamin and mineral has a recommended amount, which is what you should get each day for good health. Most of them also have what is called a “tolerable upper intake level” or UL. Getting more than the UL can cause health problems. Other vitamins and minerals appear to be safe at any dose, while a few have a UL only under certain circumstances.

Which vitamins and minerals fall into which category? Here’s the breakdown:

Nutrients with ULs: calcium, choline, copper, fluoride, iodine, iron, manganese, molybdenum, nickel, phosphorus, selenium, vitamin B6, vitamin C, vitamin D, and zinc

Stay under the UL each day for these nutrients to avoid health problems unless your healthcare provider recommends more. For example, very high doses of vitamin B6 can cause severe nerve damage and too much iron can be fatal.

The ULs for these nutrients include what you get from food, beverages, fortified foods (including many breakfast cereals), and dietary supplements. But it’s unlikely you’ll go above the UL from food and beverages alone.

Nutrients with ULs, but only from dietary supplements and fortified foods: folate, magnesium, niacin, and vitamin E

These vitamins and minerals, as found naturally in food and beverages, won’t cause any health problems. But they can if you get amounts above the UL from supplements or fortified foods.

One nutrient with a UL, but only for certain forms: vitamin A

Vitamin A exists in two main forms: preformed vitamin A—such as retinol and retinyl palmitate—in animal products (including meat, poultry, fish, and dairy products); and beta-carotene (in fruits, vegetables, and other plant foods). Dietary supplements can contain both forms.

Only preformed vitamin A has a UL because high amounts can cause health problems, such as birth defects during pregnancy and liver damage. Beta-carotene has no UL because high amounts don’t cause these problems.

Nutrients with no ULs: biotin, chromium, pantothenic acid, riboflavin, thiamin, vitamin B12, and vitamin K

These nutrients have no identified safety concerns, even at high doses. But there’s no reason to get more than recommended amounts unless your healthcare provider recommends it.

What’s the bottom line?

Most vitamins and minerals have upper limits known as ULs, so there is a range of safe intake between the recommended amounts and the ULs. Check the labels of dietary supplements and fortified foods to see the amounts of vitamins and minerals they contain. Be careful about doubling-up on supplements or taking more than the serving size listed on product labels. And talk with your healthcare provider to determine which supplements, if any, might be valuable for you.

Vitamins help our bodies grow and develop normally. The best way to get enough vitamins is to eat a balanced diet with a variety of foods. Knowing about different vitamins and what they do can help you to make sure you get enough of the vitamins that you need.

Antioxidants

Antioxidants are substances that may prevent or delay some types of cell damage. Examples include beta-carotene, lutein, lycopene, selenium, and vitamins C and E. They are found in many foods, including fruits and vegetables. They are also available as dietary supplements. Most research has not shown antioxidant supplements to be helpful in preventing diseases.

Daily Value (DV)

The Daily Value (DV) tells you what percentage of a nutrient one serving of that food or supplement provides compared to the recommended amount.

Dietary Supplements

A dietary supplement is a product you take to supplement your diet. It contains one or more dietary ingredients (including vitamins; minerals; herbs or other botanicals; amino acids; and other substances). Supplements do not have to go through the testing that drugs do for effectiveness and safety.

Fat-Soluble Vitamins

Fat-soluble vitamins include vitamins A, D, E, and K. The body stores fat-soluble vitamins in the liver and fatty tissues.

Folate

Folate is a B-vitamin that is naturally present in many foods. A form of folate called folic acid is used in dietary supplements and fortified foods. Our bodies need folate to make DNA and other genetic material. Folate is also needed for the body’s cells to divide. It is important for women to get enough folic acid before and during pregnancy. It can prevent major birth defects of the baby's brain or spine.

Multivitamin/Mineral Supplements

Multivitamin/mineral supplements contain a combination of vitamins and minerals. They sometimes have other ingredients, such as herbs. They are also called multis, multiples, or simply vitamins. Multis help people get the recommended amounts of vitamins and minerals when they cannot or do not get enough of these nutrients from food.

Niacin

Niacin is a nutrient in the vitamin B complex. The body needs it in small amounts to function and stay healthy. Niacin helps some enzymes work properly and helps the skin, nerves, and digestive tract stay healthy.

Recommended Dietary Allowance (RDA)

Recommended Dietary Allowance (RDA) is the amount of a nutrient you should get each day. There are different RDAs based on age, gender, and whether a woman is pregnant or breastfeeding.

Vitamin A

Vitamin A plays a role in your vision, bone growth, reproduction, cell functions, and immune system. Vitamin A is an antioxidant. It can come from plant or animal sources. Plant sources include colorful fruits and vegetables. Animal sources include liver and whole milk. Vitamin A is also added to foods like cereals.

Vitamin B6

Vitamin B6 is present in many foods and is added to other foods. The body needs vitamin B6 for many chemical reactions involved in metabolism. Vitamin B6 is involved in brain development during pregnancy and infancy. It also is involved in immune function.

Vitamin B12

Vitamin B12 helps keep the body’s nerve and blood cells healthy. It helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia that makes people tired and weak. Vitamin B12 is found naturally in a wide variety of animal foods. It is also added to some fortified foods and is found in most multivitamin supplements.

Vitamin C

Vitamin C is an antioxidant. It is important for your skin, bones, and connective tissue. It promotes healing and helps the body absorb iron. Vitamin C comes from fruits and vegetables. Good sources include citrus, red and green peppers, tomatoes, broccoli, and greens. Some juices and cereals have added vitamin C.

Vitamin D

Vitamin D helps your body absorb calcium. Calcium is one of the main building blocks of bone. A lack of vitamin D can lead to bone diseases such as osteoporosis or rickets. Vitamin D also has a role in your nerve, muscle, and immune systems. You can get vitamin D in three ways: through your skin (from sunlight), from your diet, and from supplements. Your body forms vitamin D naturally after exposure to sunlight. However, too much sun exposure can lead to skin aging and skin cancer, so many people try to get their vitamin D from other sources. Vitamin D-rich foods include egg yolks, saltwater fish, and liver. Some other foods, like milk and cereal, often have added vitamin D. You can also take vitamin D supplements. Check with your health care provider to see how much you should take.

Vitamin E

Vitamin E is an antioxidant. It plays a role in your immune system and metabolic processes. Most people get enough vitamin E from the foods they eat. Good sources of vitamin E include vegetable oils, margarine, nuts and seeds, and leafy greens. Vitamin E is added to foods like cereals. It is also available as a supplement.

Vitamin K

Vitamin K helps your body by making proteins for healthy bones and tissues. It also makes proteins for blood clotting. There are different types of vitamin K. Most people get vitamin K from plants such as green vegetables and dark berries. Bacteria in your intestines also produce small amounts of another type of vitamin K.

Vitamins

Vitamins are substances that our bodies need to develop and function normally. They include vitamins A, C, D, E, and K, choline, and the B vitamins (thiamin, riboflavin, niacin, pantothenic acid, biotin, vitamin B6, vitamin B12, and folate/folic acid).

Water-Soluble Vitamins

Water-soluble vitamins include all the B vitamins and vitamin C. The body does not easily store water-soluble vitamins and flushes out the extra in the urine.

Q. Where can I find out how much of each vitamin and mineral I need?

A. To get a list of all vitamins and minerals and how much you need, check out the free online tool from the U.S. Department of Agriculture. Just input a few pieces of information about yourself including your age, height, and weight. You also can get a list of your daily calorie, protein, and other nutritional needs. Keep in mind that the amounts of vitamins and minerals you need include everything you get from food and beverages—you may or may not need a dietary supplement to achieve these amounts. Talk with your health care provider to help you determine which supplements, if any, might be valuable for you.

Q. How can I get more information about a particular dietary supplement such as whether it is safe and effective?

A. Scientific evidence supporting the benefits of some dietary supplements (for example, vitamins and minerals) is well established for certain health conditions, but others need further study.

Research studies in people to prove that a dietary supplement is safe are not required before the supplement is marketed, unlike for drugs. This is due to the way dietary supplements are regulated by the U.S. Food and Drug Administration (FDA). It is the responsibility of dietary supplement manufacturers/distributors to ensure that their products are safe and that their label claims are truthful and not misleading. If the FDA finds a supplement to be unsafe once it is on the market, only then can it take action against the manufacturer and/or distributor, such as by issuing a warning or requiring the product to be removed from the marketplace.

The manufacturer does not have to prove that the supplement is effective, unlike for drugs. The manufacturer can say that the product addresses a nutrient deficiency, supports health, or reduces the risk of developing a health problem, if that is true. If the manufacturer does make a claim, it must be followed by the statement “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.”

Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions. Supplements should not replace prescribed medications or the variety of foods important to a healthful diet.

Do not self-diagnose any health condition. Work with your health care provider to determine how best to achieve optimal health. Also, check with your health care provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.

Q. Where can I find information about the use of dietary supplements for a particular health condition or disease?

A. Scientific evidence supporting the benefits of some dietary supplements (for example, vitamins and minerals) is well established for certain health conditions, but others need further study. Whatever your choice, supplements should not replace prescribed medications or the variety of foods important to a healthy diet.

Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions.

Do not self-diagnose any health condition. Work with your health care provider to determine how best to achieve optimal health. Also, check with your health care provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.

Q. What does the Supplement Facts label on a dietary supplement tell me?

A. All products labeled as dietary supplements carry a Supplement Facts label that is similar to the Nutrition Facts label found on food products. It lists the active ingredients and their amounts, plus other added ingredients like fillers, binders, and flavorings. It also gives a suggested serving size, but you and your health care provider might decide that a different amount is more appropriate for you.

In the Supplement Facts label, the amounts of vitamins, minerals, and other nutrients like dietary fiber are listed as a percentage of the Daily Value (%DV). Each nutrient has one DV that applies to all people aged 4 and older. For example, the DV for vitamin C is 90 milligrams (mg) and the DV for the B-vitamin biotin is 30 micrograms (mcg).

The %DV allows you to see how much a product contributes to your approximate daily needs for that nutrient. For example, if a supplement provides 50% of the DV for calcium, it contributes about half of your daily needs for calcium.

Q. What is the difference between the RDA and DV for a vitamin or mineral?

A. Many terms are used when referring to either the amount of a particular nutrient (such as calcium or vitamin D) you should get or the amount in a food or dietary supplement. The two most common are the Recommended Dietary Allowance (RDA) and the Daily Value (DV). These terms can be confusing.

RDAs are recommended daily intakes of a nutrient for healthy people. They tell you how much of that nutrient you should get on average each day. RDAs are developed by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine. They vary by age, sex, and whether a woman is pregnant or breastfeeding; so there are many different RDAs for each nutrient.

DVs, established by the U.S. Food and Drug Administration (FDA), are used on food and dietary supplement labels. For each nutrient, there is one DV for all people ages 4 years and older. Therefore, DVs aren’t recommended intakes, but suggest how much of a nutrient a serving of the food or supplement provides in the context of a total daily diet. DVs often match or exceed the RDAs for most people, but not in all cases.

DVs are presented on food and supplement labels as a percentage. They help you compare one product with another. As an example, the %DV for calcium on a food label might say 20%. This means it has 260 milligrams (mg) of calcium in one serving because the DV for calcium is 1,300 mg/day. If another food has 40% of the DV for calcium, it’s easy to see that it provides much more calcium.

Q. What are the upper limits for vitamins and minerals?

A. Our bodies need vitamins and minerals for many things, like breaking down the food we eat, making bones and DNA, helping muscles contract, and maintaining immunity. But there’s no reason to get more than you need, and some nutrients can be dangerous in large amounts.

Each vitamin and mineral has a recommended amount, which is what you should get each day for good health. Most of them also have what is called a “tolerable upper intake level” or UL. Getting more than the UL can cause health problems. Other vitamins and minerals appear to be safe at any dose, while a few have a UL only under certain circumstances.

Which vitamins and minerals fall into which category? Here’s the breakdown:

• Nutrients with ULs: calcium, choline, copper, fluoride, iodine, iron, manganese, molybdenum, nickel, phosphorus, selenium, vitamin B6, vitamin C, vitamin D, and zinc

  Stay under the UL each day for these nutrients to avoid health problems unless your health care provider recommends more. For example, very high doses of vitamin B6 can cause severe nerve damage and too much iron can be fatal. The ULs for these nutrients include what you get from food, beverages, fortified foods (including many breakfast cereals), and dietary supplements. But it’s unlikely you’ll go above the UL from food and beverages alone.

• Nutrients with ULs, but only from dietary supplements and fortified foods: folate, magnesium, niacin, and vitamin E

  These vitamins and minerals, as found naturally in food and beverages, won’t cause any health problems. But they can if you get amounts above the UL from supplements or fortified foods.

• One nutrient with a UL, but only for certain forms: vitamin A

  Vitamin A exists in two main forms: preformed vitamin A—such as retinol and retinyl palmitate—in animal products (including meat, poultry, fish, and dairy products); and beta-carotene (in fruits, vegetables, and other plant foods). Dietary supplements can contain both forms.

  Only preformed vitamin A has a UL because high amounts can cause health problems, such as birth defects during pregnancy and liver damage. Beta-carotene has no UL because high amounts don’t cause these problems.

• Nutrients with no ULs: biotin, chromium, pantothenic acid, riboflavin, thiamin, vitamin B12, and vitamin K

  These nutrients have no identified safety concerns, even at high doses. But there’s no reason to get more than recommended amounts unless your health care provider recommends it.