Do prebiotics help gut health? See what science says

Walking through the aisles of any health food store or drugstore, you will likely find prebiotic supplements. They are packaged as powders, gummies, pills, and drinks, and claim to improve digestion, boost the immune system, lower blood sugar, and more.

According to market research firm Grand View Research, the prebiotics market is expected to grow about 15% per year from 2022 to 2030 in the United States — in part due to growing concerns among consumers about bowel problems like constipation, irritable bowel, acid reflux and inflammatory bowel disease.

But what exactly are prebiotics? And do you need to take them for good health?

What are prebiotics?

People often confuse prebiotics with probiotics — the live microorganisms found in foods like kimchi and some yogurts, as well as in supplements meant to benefit health.

But prebiotics are substances that promote the growth of beneficial microbes in the gut. They can be found in fiber-rich foods such as green bananas, asparagus, artichokes, garlic, onions, barley and wheat bran.

Justin L. Sonnenburg, professor of microbiology and immunology at Stanford University, said prebiotic supplements often contain purified types of dietary fiber that humans cannot digest.

The main purpose of prebiotics is to feed the diverse mix of beneficial bacteria that the gut needs to thrive, Sonnenburg said. A thriving microbiome has been linked to a number of health benefits, including reduced risks of certain conditions such as diabetes and obesity.

Gail Cresci, a microbiome researcher in pediatric gastroenterology at the Cleveland Clinic Children’s Hospital, said that prebiotic and probiotic supplements are sometimes packaged together in a supplement. And some types of fiber supplements are also considered prebiotics, Sonnenburg said.

Do prebiotics help the gut?

Several small studies have found that prebiotics – in supplemental and dietary form – are associated with regulating intestinal inflammation, relieving constipation and supporting digestive health. But there is less research on prebiotics than on probiotics in general, and their findings have been mixed and limited. More research is needed, Sonnenburg said.

In a 2018 study of 44 people with certain gastrointestinal disorders that caused flatulence, for example, researchers investigated how taking a prebiotic supplement helped reduce symptoms compared with following a low-FODMAP (oligosaccharide) diet. , fermentable disaccharides, monosaccharides and polyols”). After four weeks, both methods were equally effective.

In another 2018 study, researchers reviewed several dozen studies on the effectiveness of prebiotics, probiotics, synbiotics (a mixture of probiotics and prebiotics), and antibiotics in managing irritable bowel syndrome.

They found few studies showing that prebiotics, alone or in combination with probiotics, benefited patients with the disease. A subsequent review of 33 randomized controlled trials in 2020 reached similar conclusions.

Some evidence suggests that prebiotic supplements may help with constipation by encouraging more regular, frequent, well-formed bowel movements, Cresci said.

In fact, if you’re constipated, prebiotics can induce a laxative effect, said Kelly Swanson, a professor of animal and nutritional sciences at the University of Illinois at Urbana-Champaign.

There is also preliminary research suggesting they may help strengthen the immune system, Swanson added, but this evidence is inconclusive. He said, however, that he has researched how specific prebiotics can affect the abundance and activity of microbes in the gut microbiome, and that they “clearly modify” the bacteria in our gut in beneficial ways.

Reezwana Chowdhury, assistant professor of medicine at Johns Hopkins Medicine, said she is not aware of any data showing significant dangers associated with taking prebiotic supplements. But there’s also not enough evidence showing that prebiotics are beneficial in treating conditions like irritable bowel syndrome or diarrhea, she said, which is why she never recommended prebiotic supplements to her patients.

If you decide to try them, these supplements are generally safe and typically have few side effects, Swanson said. He noted that some people may experience more flatulence and loose stools after taking them, especially if prebiotics are taken in higher than recommended amounts. To minimize this risk, Swanson suggested taking no more than 5 grams a day.

And don’t expect the supplement to radically transform your gut, Cresci said.

“The prebiotic is not going to save the day of a bad diet,” she said. “There is no magic solution to this.”

What can you do instead of taking a prebiotic?

When it comes to nourishing the good bacteria in your gut, Sonnenburg said, eating a high-fiber diet with lots of fruits and vegetables is likely to be best for you.

We each have hundreds of species of bacteria flourishing in our gut, and “it’s very difficult to imagine how putting a purified prebiotic in that community could promote the kind of biodiversity you need in your gut microbiome,” he said.

That doesn’t mean you have to eat a pound of asparagus every day for good health, he said. But making a point of eating bananas during the week, he said, or swapping sugary pastries for breakfast with healthier options like oatmeal mixed with nuts and berries, will help the organ’s good bacteria thrive.

Adding fiber to your diet, which evidence suggests the average person in the United States would benefit from, will give you many of the same benefits as prebiotics, Sonnenburg said, as fiber encourages the growth of beneficial bacteria in the gut.

The American Heart Association recommends that most people consume at least 25 to 30 grams of dietary fiber a day.

To achieve this goal, experts at the University of California at San Francisco recommend at least five servings of fruits and vegetables a day and at least one serving of whole grains at each meal.

You can increase your fiber intake by adding lentils and vegetables to soups and salads or by blending chia seeds into shakes. You can also make some intentional changes to your diet: replace white rice with brown rice, and when buying cereal, choose a product with at least 5 grams of fiber per serving. These changes can have a more transformative effect on your gut than taking a prebiotic.

“Very few things are solved by just taking a pill,” Swanson said.

Translated by Luiz Roberto M. Gonçalves