Why is the gut important?

When talking about your health, the word “gut” means the stomach and intestines. The medical word for the gut is the gastrointestinal, or GI, system. Food first must pass through the esophagus to get to the stomach, then the small intestine, the large intestine, and finally the rectum. The large intestine is also called the colon. We often think of the gut as a long, hollow tube for food to pass through, but it is much more than that. The gut plays an important role in the body. Science continues to make new discoveries about all of the important things it does, such as the following:

• Break down food into digestible parts
• Absorb nutrients like vitamins, minerals, carbohydrates, protein, and fat
• Absorb water
• Get rid of waste products, including toxins
• Serve as a “gateway” for the immune system to
  • Keep out bacteria, viruses, fungi, and parasites that can cause disease
  • Help our immune system learn to tell the difference between what is dangerous and what is safe
• Receive signals from the brain through the nervous system
• Send signals back to the brain through the nervous system

The gut can’t do all of this on its own. It needs the help of the microbes that live in the gut. These microbes are mostly bacteria and a few yeast. Altogether, they are called the “gut microbiota.” Believe it or not, there are trillions of microbes that live in the gut. This is more than the number of cells in the entire human body! We as human beings evolved a complex relationship with these microbes. We now depend on each other to live. It’s true – your life actually depends on the microbes in your gut!

How does my gut health connect to other parts of my whole health?

There are obvious ways in which the gut is connected to your health and wellbeing. For example, if you get a “stomachache” and have nausea or abdominal pain, or you get severe heartburn, this can interfere with your daily life. Diseases such as celiac disease, Crohn’s disease, or cancer can have an even bigger impact. They may even become quite serious. Science continues to discover other ways in which gut health relates to practically all systems of the body. For example, what happens in your gut may be directly related to all of the following:

• Autoimmune diseases (where the body attacks itself), such as rheumatoid arthritis
• Bone health and osteoporosis (disease resulting in weak bones)
• Metabolic diseases (diseases that involve chemical changes in the body that support life) such as diabetes and obesity
• Heart disease
• Mental health, including depression and anxiety.

Why are these bacteria in my gut so important?

Science is discovering that the gut microbiota play a central role in how gut health affects the rest of the body. How does this happen, you might ask? The action happens with the cells of the gut and their “neighborhood.”

1. Healthy competition. There are “helpful bacteria” that live in your gut. These bacteria support healthy gut functioning and whole health. There are also “harmful bacteria.” They can cause disease when there are too many of them. It is not necessary to have 100% helpful bacteria. The important thing is to have diversity and a good balance. Competition between different types of bacteria living in the gut is happening all the time.

2. Intestinal barrier. The cells that line the intestine need to let some things into the bloodstream and keep some things out. This barrier changes based on signals that the bacteria send to the intestine cells. The signals tell the cells to either tighten up the spaces in between or loosen them. When these spaces are too loose, they become “leaky” and can let too many things into the blood. Helpful bacteria tell the intestines to keep the cells nice and tight, so it’s not too leaky.

3. Mucus layer. On top of the intestinal cells is the mucus layer. This mucus layer is very important and also works as a kind of barrier. It is also where the bacteria live and a lot of digestion happens. Helpful bacteria help to keep this mucus layer nice and thick.

4. Immune system. Your own immune cells move throughout your whole body. There are special areas that line the intestine where they gather in large numbers. In these areas, the immune system interacts with the different bacteria in the gut, together with the things we eat. The immune system then produces signals that are then passed on throughout your body

5. Nutrition. The bacteria in your gut help break down food into nutrients that can be absorbed. They can also even use these breakdown products to build new nutrients, such as vitamins, that we would otherwise not be able to get enough of.

6. Metabolism. Bacteria in our gut also make products that then turn on or off signals in our hormone system. These hormone signals then affect our metabolism – including appetite, hunger, and whether we store or burn fat.

7. Mind and emotions. The gut has its own branch of the nervous system, called the enteric nervous system. This system is so large that it’s sometimes called our “second brain.” Bacteria directly make signals or stimulate the intestinal cells to make signals that the enteric nervous system uses. These signals talk to the central nervous system, including the brain. This connection is called the gut-brain axis. This means that the bacteria in your gut can actually affect your mind and emotions, such as depression and anxiety.

8. Repair. The bacteria in your gut also affect how your body repairs damaged cells. When damaged cells are not repaired well, it may, in some people, lead to cancer. For example, certain types of bacteria are more common in people who get colon cancer.

What can happen when the bacteria in the gut are out of balance?

When you have a good balance of helpful bacteria in the gut, the eight areas above are also in better balance. On the other hand, when you have more of certain types of bacteria and fewer helpful bacteria in the gut, there is more chance of having health problems. In that case, one or more of these eight areas might not work well. Also, when these areas are not working well, there is more inflammation. That’s because there is more stress that the body has to deal with. Inflammation is a part of many diseases. This is how the bacteria in your gut may play a role in whether you gain too much weight, have high blood pressure, get diabetes, have a fatty liver, or are more at risk for a heart attack.

Is there actually research showing that the bacteria in the gut can affect the brain and mental health?

Yes, a growing field of research shows how closely connected the gut and the brain are. So far, it looks like bacteria, along with the cells in the intestine, help to make chemicals that communicate with nerves and the brain. These chemicals are actually the same type that medications for depression and anxiety (such as Prozac) affect. This seems to be one way in which gut bacteria may affect depression and anxiety. A very interesting research study used a fermented milk drink containing healthy bacteria. The study compared brain scans of women who drank this milk to women who did not drink it. The women who drank the fermented milk had changes in an area of the brain that handles emotions.

Everyone has pain or discomfort in their gut occasionally. Maybe you ate something that didn’t agree with you. Or you had an infection that made you sick to your stomach for a few days.

But if pain and other gut symptoms go on for weeks or longer, something more serious might be wrong. Digestive system diseases and disorders are very common. Around 60 to 70 million people in the U.S. live with a digestive disease.

It’s important not to ignore symptoms in your gut. Many digestive disorders are easiest to treat when they first develop.

Potential Causes

One of the most serious gut disorders is inflammatory bowel disease (IBD), although it’s not very common. IBD occurs when immune system cells in the gut overreact to a perceived threat to your body. Often, that “threat” is the normal bugs that make up the microbiome—the microscopic creatures like bacteria, fungi, and viruses—that live in your gut. This overreaction can damage the digestive (gastrointestinal or GI) tract.

The two main types of IBD are ulcerative colitis and Crohn’s disease. “Crohn’s can occur anywhere in the digestive tract, from the mouth to the anus,” says Dr. Judy Cho, an IBD expert at Mount Sinai. Ulcerative colitis happens only in the large intestine.

These two diseases also differ in how deeply they can damage tissue. “Ulcerative colitis causes damage in the gut lining,” explains Dr. Dermot McGovern, who studies IBD at Cedars-Sinai. “Crohn’s disease can go all the way through the gut.” Severe cases of Crohn’s can lead to narrowing of the intestines and even holes in the gut.

Other conditions can harm the lining of the stomach and lead to a type of inflammation called gastritis. The most common cause of gastritis is infection with bacteria called Helicobacter pylori. Other causes include the long-term use of some pain medications. If left untreated, gastritis can lead to painful ulcers.

Twelve percent of people in the U.S. have irritable bowel syndrome (IBS). “This is a very common disorder. It’s characterized by abdominal pain, bloating, and changes in bowel habits,” says Dr. Anthony Lembo, an IBS researcher at Beth Israel Deaconess Medical Center.

Researchers don’t understand exactly what causes IBS. It may have different causes in different people. Sometimes it involves problems with how the brain and gut work together.

Other things that can cause pain and discomfort in the GI tract are acid reflux or food sensitivities.

Pinpointing the Problem

It can be tricky to diagnose a digestive disease because they share a lot of symptoms, explains Cho. Symptoms of many gut conditions include pain, gassiness, bloating, and diarrhea.

“But for IBD, there are several red-flag symptoms,” she says. These are blood in the stool, weight loss, and signs of inflammation found in a blood test. A sign of IBD in children is failure to grow, Cho adds.

IBS can give some people diarrhea and others constipation. Some people go back and forth between the two.

Gastritis and food sensitivities can also cause long-term gut discomfort. To figure out what’s causing gut troubles, doctors may need to run a variety of tests. These can include blood tests and a stool test to look for infection.

Some people may have an imaging test, such as a CT scan. Others may need to have an endoscopy. Endoscopy uses a long, flexible tube with a tiny camera on the end to look in the intestines or stomach.

Treating Pain and Discomfort

While symptoms for different gut disorders can be similar, treatments vary widely. For gastritis caused by bacterial infection, antibiotics are used to kill the germs. If medications are causing gastritis, switching to a different kind of drug will usually allow the stomach to heal.

Food sensitivities can be managed by changing your diet. A nutritionist can help you figure out what foods might be irritating your gut. Acid reflux can also often be improved by changes in your diet and medication.

Treatment isn’t one-size-fits-all for IBS, Lembo explains, because it can have different causes. Some people can get some relief by adjusting their diet. (See the Wise Choices box for foods that can trigger gut symptoms.)

“We also tell patients to eat two to three meals a day, maybe have a snack or two. But don’t eat all day long. Give your gut a chance to rest,” he says.

And while stress doesn’t cause IBS, it can trigger flare-ups of symptoms in many people, says Lembo. Stress reduction strategies and cognitive behavior therapy—a type of talk therapy—can help some people manage symptoms of IBS.

IBD is harder to treat than most gut disorders. “It’s impossible to cure IBD right now,” says Cho. Treatments focus on stopping inflammation long enough to allow the gut tissue to heal, she explains.

Some medications used for IBD control inflammation. Other newer drugs suppress the immune system. But these newer drugs can have serious side effects and are usually only used when others don’t work.

“Research has discovered that the earlier you use these medications, the more likely you are to respond,” says McGovern. So, people with high-risk disease may get these drugs first now, he explains.

Looking for Better Treatments

Researchers are searching for new ways to prevent and manage gut disorders. Lembo, for example, is testing whether peppermint oil can help the gut muscles relax in people with IBS.

Existing treatments for IBD only work for about a third of people who try them. And even then, McGovern says, they may lose their effects over time.

Both Cho and McGovern are working to understand the genetics of IBD. This information could be used at all stages of the disease, explains Cho. For example, if a test could identify children at higher risk of developing IBD later in life, “theoretically it could be prevented,” she says. Strategies could include giving anti-inflammatory drugs before IBD develops or changing the gut microbiome to prevent an immune attack.

“And what we’re all interested in is: Can we use some of these genetic signatures to identify new drug targets for IBD?” adds McGovern. That could also eventually help predict who would most likely benefit from a drug, he says.

One of the newest drugs being tested for IBD was based on a genetic discovery, Cho explains. “There’s increasing precision in treatment,” she says. “Using genetic knowledge to help choose therapies for IBD is something that I think is doable in the next five to 10 years.”

For now, talk with your doctor if gut discomfort or pain are impacting your quality of life. Available treatments can help most people get their insides back in order again.

Gut Trigger Foods

Not all people with gut disorders have problems with the same foods. But some foods that commonly cause gut discomfort include:

• Dairy products
• Caffeine
• Carbonated drinks
• Sugar, candy, and junk food
• Fruit juices
• Beans
• Cruciferous vegetables, like broccoli and cauliflower

You feel something rising in your throat. It burns and tastes acidic. Now you feel it behind your breastbone.

Is it heartburn? Is it GERD? Is it acid reflux? Are they all the same?

We've compiled a simple overview to help you navigate this often tricky area of digestive conditions.

Acid reflux: The cause

Acid reflux is when the contents of your stomach—like food or acids—go in the wrong direction. They travel from your stomach back to your throat through the tube connecting them, your esophagus.

When you have acid reflux, you may taste food or stomach acid in the back of your mouth. This can be uncomfortable and make you feel sick. Acid reflux is also referred to as GER (gastroesophageal reflux).

Heartburn: The symptom

Acid reflux causes heartburn, which is a burning feeling behind your breastbone, in your neck, or in your throat. This feeling is often worse after eating, in the evening, or when lying down or bending over. Being pregnant or overweight can make heartburn more likely.

GERD: The more serious cause

GERD stands for gastroesophageal reflux disease (GERD).

Like its name suggests, GERD is a more serious version of acid reflux. They can both cause heartburn. Often people who experience heartburn more than twice a week have GERD.

GERD happens when the closure in your lower esophagus—which is near your stomach—becomes weak or relaxes when it should not. Symptoms include heartburn, regurgitation, chest pain, dry cough, shortness of breath, or trouble swallowing.

Treating GERD may require prescription medications. Occasionally, surgery or other procedures may be necessary.

If you suspect you have GERD, make sure to see your provider or a gastroenterologist, a doctor who focuses on the digestive system. This can help prevent future damage to your esophagus, or cancer.

Most of us feel some discomfort in our guts from time to time. It may be because we’re nervous about something, or perhaps we ate something that didn’t agree with us. But if you regularly feel aches in your abdomen, it might be a sign of a disorder called irritable bowel syndrome.

Irritable bowel syndrome affects about 1 in 5 Americans. It occurs more often in women than men, and begins before the age of 35 in about half the people who get it.

There’s no medical test to identify irritable bowel syndrome. Instead, doctors make a diagnosis based on the patient’s symptoms. The most common symptoms include bloating and pain in the abdomen, along with changes in bowel habits. People with irritable bowel syndrome may have constipation, diarrhea or both.

Irritable bowel syndrome doesn’t lead to cancer or other health problems. But its discomfort can be difficult to live with. The severe or frequent abdominal pain it can bring often leads people to visit a doctor.

Physicians and researchers don’t know for sure what causes irritable bowel syndrome. One possibility is that it comes from changes in the way that the brain and the gut communicate. Dr. Emeran Mayer at the University of California, Los Angeles, is an NIH-funded scientist who’s working to find treatments to correct altered brain-gut interactions.

“Most people would agree that stress plays an important role in triggering symptom flares in irritable bowel syndrome,” says Mayer.

Many patients first notice symptoms after a stressful event, like losing a loved one or changing jobs. People with irritable bowel syndrome often report higher levels of stress or anxiety. Stress reduction strategies and cognitive behavioral therapy, a type of talk therapy, can help relieve the symptoms of irritable bowel syndrome.

Some researchers suspect that irritable bowel syndrome can be caused by a change in gut bacteria. The gut is usually filled with helpful bacteria, which our bodies need to digest food. But sometimes the types of bacteria can change, like after taking certain medications. For people with this type of irritable bowel syndrome, a supplement of probiotics—a collection of live, healthful bacteria—might help. Probiotics are available as capsules, tablets and powders, and they’re found in some dairy foods, such as yogurts with live active cultures. The potential benefits of probiotics, however, are still under study.

Many people with irritable bowel syndrome find that certain foods can make them feel worse. “There is no specific irritable bowel syndrome diet,” says Mayer. “Irritable bowel syndrome patients are generally more sensitive to a variety of foods.”

If you have irritable bowel syndrome, try keeping a diary of the foods you eat and how they make you feel. Then, you and your doctor can decide together if you should try making changes to your diet.

Every case of irritable bowel syndrome is unique, so if you have symptoms that disrupt your life, don’t suffer in silence. Your doctor can work with you to find the treatment that works best for you.

Signs of Irritable Bowel Syndrome

• Bloating
• Distension and discomfort of the abdomen
• Abdominal pain
• Constipation
• Diarrhea

Your stomach lining has an important job. It makes acid and enzymes that help break down food so you can extract the nutrients you need. The lining also protects itself from acid damage by secreting mucus. But sometimes the lining gets inflamed and starts making less acid, enzymes and mucus. This type of inflammation is called gastritis, and it can cause long-term problems.

Some people think they have gastritis when they have pain or an uncomfortable feeling in their upper stomach. But many other conditions can cause these symptoms. Gastritis can sometimes lead to pain, nausea and vomiting. But it often has no symptoms at all. If left untreated, though, some types of gastritis can lead to ulcers (sores in the stomach lining) or even stomach cancer.

People used to think gastritis and ulcers were caused by stress and spicy foods. But research studies show that bacteria called Helicobacter pylori are often to blame. Usually, these bacteria cause no symptoms. In the United States, 20% to 50% of the population may be infected with H. pylori.

H. pylori breaks down the inner protective coating in some people’s stomachs and causes inflammation. “I tell people H. pylori is like having termites in your stomach,” says Dr. David Graham, an expert in digestive diseases at Baylor College of Medicine in Texas. “You usually don’t know you have termites until someone tells you, and you ignore it at your own risk.” H. pylori can spread by passing from person to person or through contaminated food or water. Infections can be treated with bacteria-killing drugs called antibiotics.

One type of gastritis, called erosive gastritis, wears away the stomach lining. The most common cause of erosive gastritis is long-term use of medications called non-steroidal anti-inflammatory drugs. These include aspirin and ibuprofen. “When you stop taking the drugs, the condition usually goes away,” says Graham. Doctors might also recommend reducing the dose or switching to another class of pain medication.

Less common causes of gastritis include certain digestive disorders (such as Crohn’s disease) and autoimmune disorders, in which the body’s protective immune cells mistakenly attack healthy cells in the stomach lining.

Gastritis can be diagnosed with an endoscope, a thin tube with a tiny camera on the end, which is inserted through the patient’s mouth or nose and into the stomach. The doctor will look at the stomach lining and may also remove some tissue samples for testing. Treatment will depend on the type of gastritis you have.

Although stress and spicy foods don’t cause gastritis and ulcers, they can make symptoms worse. Milk might provide brief relief, but it also increases stomach acid, which can worsen symptoms. Your doctor may recommend taking antacids or other drugs to reduce acid in the stomach.

Talk with a health care provider if you’re concerned about ongoing pain or discomfort in your stomach. These symptoms can have many causes. Your doctor can help determine the best course of action for you.

Watch for Ulcers

Gastritis can lead to ulcers over time. Symptoms of ulcers include pain between the belly button and breastbone that:

• starts between meals or during the night
• briefly stops if you eat or take antacids
• lasts for minutes to hours
• comes and goes for several days or weeks

Contact your doctor right away if you have:

• sudden sharp stomach pain that doesn’t go away
• black or bloody stools
• vomit that is bloody or looks like coffee grounds

Have you ever wondered why some people enjoy exercise while others find it unbearable? New research hints at a surprising connection: the gut microbiome! You read that right—the trillions of tiny organisms, or microbes, that live in our digestive system may play a role in whether we feel like exercising.

We know that the bacteria in our guts are important for our digestion and overall health. Recent research suggests that our guts also communicate with our brains. This "gut-brain axis" is linked to mood, stress, and maybe even our motivation to exercise.

Mice, microbes, and motivation

How exactly might gut microbes influence our motivation to exercise? To answer that question, NIH-funded researchers studied exercise performance in mice. They found that mice ran less on their exercise wheel when they had depleted gut microbiomes (meaning fewer microbes). They also got tired faster. This suggests these microbes might have a say in how much the mice wanted to exercise…and how much exercise they were physically able to tolerate.

Exercise increases dopamine, a brain chemical associated with pleasure, motivation, and reward (if you’ve ever experienced a “runner’s high,” that’s because of dopamine). As expected, exercise increased dopamine in the mice with healthy gut microbiomes, which motivated them to keep moving. But this increase in dopamine didn’t happen when the mice’s microbiomes were depleted.

The gut talks to the brain

Digging deeper, the researchers learned that bacteria in the gut produce a certain chemical that communicates with the brain. During exercise, these chemicals tell the brain to release more dopamine. The extra dopamine makes exercise feel more rewarding and energizing. When this communication pathway was interrupted, the mice lost their motivation to move.

What does this mean for human health?

It’s hard to say for sure. While motivation is important, there’s more to the story for people than for these furry research subjects. This research happened in a controlled setting to allow researchers to isolate the effects of gut bacteria. Our lives are more complex, and scientists are still exploring how our gut bacteria might influence our exercise choices.

We’ll need more research to understand the relationship between our own gut microbes and why, when, and how we choose to move our bodies. But if it does work the same for humans, we could find new ways to make getting active more enjoyable, rewarding, and achievable for everyone.

A healthy gut is sort of like a well-functioning city, and the bacteria in our gut are sort of like people or residents of the city. A healthy city has good roads, buildings, schools, and parks. Its residents are friendly to one another. They cooperate for the sake of the whole community. They have jobs that help others. This is a two-way relationship. The community is only good as long as the residents help prevent and fix problems. And the residents can only continue to live in the city if it supports their needs. The residents also need to be provided with things that keep them happy and that help them want to stay in the city. These are things like entertainment, recreation, and food. When the city is doing well, it helps the state as well as the entire country.

In order to have a healthy gut, you need to support the community (your intestines). You need to attract friendly residents (helpful bacteria and yeast) and keep those residents happy (feed them good food and decrease stress). When all of these things happen, the healthy city (healthy gut) can then support the state and country (heathy body and mind).

How do probiotics and prebiotics support a healthy gut?

The word probiotic means actual living microbes. These are usually bacteria but sometimes certain yeast. You can eat or drink them to help create a better balance between helpful and harmful bacteria in your gut. Probiotic bacteria and yeast use fermentation. This is a process used in making certain foods, such as sauerkraut or yogurt. Beer also uses fermentation by yeast. A healthy gut has bacteria and yeast that use this process of fermentation. Probiotic foods, such as sauerkraut, contain these healthy bacteria. Thus, they can boost the gut’s own balance. Similarly, you can also add certain healthy bacteria to your gut by taking probiotic supplements.

The word prebiotic means foods that feed the good bacteria in your gut. Prebiotics encourage the good bacteria to grow. This creates a healthier balance in the gut.

You can use a combination of prebiotic foods and probiotics supplements or probiotic foods to help your gut be healthy. The goal is not to take probiotics continuously for the rest of your life. Instead, it is best to support your gut with good prebiotic food, which will help it remain healthy on its own. Some examples are below.

For you to consider:

• In general, do you feel that you have a healthy gut?
• Do you have symptoms that suggest the bacteria in your gut may be out of balance? What are they?
• How are you doing in the key areas of support (healthy diet, regular physical activity/exercise, adequate rest, stress management)? Is there one that feels right for you to focus on right now?
• Do you want to try eating more prebiotic or probiotic foods? What will you try or eat more of? Have fun with this. Consider trying something you’ve never eaten before.