by Columbia University Irving Medical Center

Credit: Unsplash/CC0 Public Domain

To restore the intestinal balance they are sure they do not have, some people turn to probiotics.

But what exactly are probiotics? Do they work? How do you know if you need one? We posed these questions and more to Columbia gastroenterologist Daniel Freedberg, MD, who studies probiotics and their effectiveness.

What are probiotics?

Probiotics are "good" bacteria taken in the hope of improving health.

What do probiotics do?

Probiotics change the bacteria that live in the gut, called the gut microbiome. The hope is that probiotics lead to more beneficial bacteria and fewer harmful ones in the gut and better digestive or overall health.

Why does everyone think they need a probiotic?

We surveyed over 500 people who were coming in for a routine colonoscopy and asked them about probiotics. About one-quarter of them had used probiotics recently. Of these, 45% said that they take probiotics to improve overall health and longevity. An overlapping 45% thought that probiotics improve gut health specifically.

Does the microbiome affect health?

The microorganisms in the human gut contribute to nutrition and protect us against illness and disease. A healthy gut has a balanced mix of different bacterial species which promotes immunity.

Compared to healthy volunteers, differences in the gut microbiota are found in people with conditions such as inflammatory bowel disease (i.e., Crohn's disease or ulcerative colitis); irritable bowel syndrome (IBS); gut infections, such as Clostridioides difficile infection; diabetes; metabolic syndrome; multiple sclerosis; non-alcoholic fatty liver disease; urinary tract infections; and psychiatric disorders, such as depression.

Though these problems have been associated with an altered gut microbiota, we don't really know whether a "bad" gut microbiota causes them. For many conditions, the "bad" microbiota seems more likely to be a consequence rather than a cause of the condition.

We also know that microbiomes vary widely in healthy people. In the Human Microbiota Project, stool samples from thousands of healthy people (those without abdominal pain, diarrhea, constipation, or other known gut problems) were examined. There was a wide range of gut bacteria, meaning that two people could have totally different gut bacteria yet both people are perfectly healthy.

What does scientific research say about probiotics?

There is scientific evidence that probiotics help for certain health issues. But not all probiotics are right for all illnesses and diseases. Some probiotic manufacturers make big claims that are not backed up by any evidence. The degree to which a probiotic can correct any issue is probably limited.

When should someone take probiotics?

The American Gastroenterological Association recommends use of probiotics in three specific situations: (1) to prevent gut infections while taking antibiotics, (2) in preterm infants, and (3) in people with inflammatory bowel disease who have a condition called pouchitis.

Most people who take probiotics do not fall into any of these three categories.

I try to steer my patients away from probiotics for the purpose of improving overall health and toward a fiber-based diet. Fiber acts like a "prebiotic" so it also changes the bacteria that live in the gut.

What is the best probiotic, if I need one?

The organisms recommended by the American Gastroenterological Association are S. boulardii (a yeast), Lactobacillus species, and Bifidobacterium species. Again, these are recommended only in a few specific situations and not for overall health. Further, probiotics have different effects in different people.

Remember that probiotics are regulated like food, not drugs. Probiotic manufacturers are not obligated to prove any health benefits of their products.

Could taking probiotics be dangerous, whether someone needs them or not?

Probably not. The bacteria that are put into probiotics vary, but they are always non-pathogenic bacterial species, meaning that you can't get a bloodstream infection or any other infection from these kinds of bacteria.

Is a stomach ache a sign your gut microbiota is imbalanced, and can it be corrected with a probiotic?

No. The medical term for a stomach ache is "abdominal pain." The most common cause of abdominal pain is gas/air in the colon. No studies have ever shown that probiotics reduce abdominal pain.

When it comes to probiotics, what's the one thing you wish everyone knew?

In the office, I encourage people to think about a healthy fiber-rich diet instead of probiotics. Dietary fiber is a prebiotic—it changes which bacteria are present in the gut. Fiber is inexpensive and natural, and by changing your dietary fiber intake you are changing your gut bacteria.

Provided by Columbia University Irving Medical Center