Prebiotics Support Digestive and Immune Health

If you don’t know much (or anything) about prebiotics — with an “e” — you are far from alone. A number of readers have expressed confusion about the difference between prebiotics and their better known cousins, probiotics… so I decided to devote a few articles to explain more about how both can be used to optimize digestive health and boost immunity. I placed a call to a medical doctor who also is highly active and respected in the world of natural medicine, Leo M. Galland, MD.

Prebiotics — What Probiotics Eat

Your high school Latin provides an easy and obvious way to differentiate prebiotics from probiotics — focus on the “pre.” Prebiotics are the predecessor. Their primary purpose is to provide nourishment to probiotics, thus helping to sustain a healthy level of these good bacteria in the gut.

Research has shown prebiotics to be beneficial for people with Crohn’s disease and ulcerative colitis. Prebiotics can serve as a natural remedy to ease constipation, and they can be helpful for a number of other digestive complaints, including constipation-associated irritable bowel syndrome (IBS) and some cases of inflammatory bowel disease. Prebiotics also help absorption of calcium and magnesium in people who have low mineral levels in their diets, and there’s some evidence that they might help prevent colon cancer as well.

Unlike probiotics, prebiotics are not bacteria — they’re a form of soluble fiber that can be found in a few complex carbohydrates. What makes them unique is their ability to pass unabsorbed through the small intestine, which makes them available to feed tissue and probiotics in the large intestine. One of the most common prebiotics is a kind of complex fructose polymer found in some plant foods called inulin (which, in spite of the similarity in names, has nothing to do with insulin). There are other kinds, too, including non-inulin prebiotics and a type called fructo-oligosaccharides (or FOS).

Are Dietary Sources Sufficient?

Some foods are rich sources of prebiotics. For instance, inulin can be found in generous amounts in Jerusalem artichokes (a potato-like tuber)… chicory… jicama… and dandelion. And many common foods contain lesser amounts of inulin and/or FOS, such as onions, garlic, leeks, bananas, tomatoes, spinach and whole wheat.

Since prebiotics aren’t abundant in these foods, it can be useful to take prebiotic supplements if you have certain types of problems.

Dr. Galland prescribes prebiotic supplements for many of his patients, he told me, noting that a typical dose can range from 4 grams to 8 grams. They come in various forms, including powders and capsules. He often prescribes…
  • Extracts of Jerusalem artichokes or extracts of chicory, best for chronic constipation.
  • FOS extracted from fruits and grains, which can be helpful for constipation and colitis.
  • Non-inulin prebiotics, which include oat beta-glucan — a soluble fiber that is separated from oats to make supplements. These have the additional benefit of lowering cholesterol. Oat beta-glucan is less likely to cause gas or bloating than inulin and can be excellent for boosting immune function, Dr. Galland said.
Start Slowly and Talk to Your Doctor

Since this is all fairly complex, it is important to consult with a physician who has expertise in treating patients with prebiotic supplements. If you and your doctor agree that prebiotics may be helpful to you, plan to start slowly and increase the dosage gradually, or your body may overrespond to added prebiotics, Dr. Galland cautions. “Let your GI tract get used to the prebiotics and shift the bacteria slowly,” he said. Stop taking them if you notice an upset stomach, gas, diarrhea, bloating and other uncomfortable digestive symptoms that don’t dissipate within a few days.

A group that is especially likely to experience such difficulties, Dr. Galland said, is people with inflammatory bowel disease — as well as some folks with other types of digestive problems. Why? While the prebiotics are not themselves irritating, they may increase production of irritants by stimulating the growth of beneficial intestinal bacteria, Dr. Galland explained. Note: Unpleasant as it may be, this actually may be a sign that the prebiotics are beginning to do their job.

Some people should avoid prebiotics altogether, including people who have fructose malabsorption, a limited ability to absorb fructose (including that found in inulin-based prebiotic supplements and inulin-containing foods such as Jerusalem artichokes). If you have this problem, you may experience gastrointestinal problems (gassiness, bloating, diarrhea) that get worse and worse if you take prebiotics. Don’t know whether this might apply to you? Here’s a clue. People with fructose malabsorption are very likely to get gassy and/or bloated or have diarrhea if they consume the sweeteners sorbitol or xylitol, because these are fermented by the same bacteria that ferment inulin.

Look for the next issue of Daily Health News, when I’ll round out this story with Dr. Galland’s intriguing advice on how to use probiotics to optimize your digestive and immune health.
Leo M. Galland, MD, founder and director, Foundation of Integrated Medicine, New York City. His Web site,, has a free online database of information about drug/supplement/food interactions.