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August 13, 2010 | Comments: 0

Prebiotics: Feeding Your Friendly Bacteria

Probiotics are “friendly” bacteria found in yogurt and other fermented foods that may have digestive and other potential health benefits. But what are prebiotics?

Prebiotics are food ingredients that nourish probiotics. Typically, prebiotics are fibers and certain sugars that we don’t digest or absorb but that the bacteria in our intestines feed on, thereby stimulating their growth and activity. Probiotics go by the names  L. acidophilus and B. bifidum, among others. Prebiotics include fructo-oligosaccharides (FOS) and inulin (a fiber-like substance).

Prebiotics occur naturally in small amounts in many carbo­hydrate-rich foods—whole grains, legumes, fruits, and vegetables. They have been added to foods for a number of years as fat replacers and fiber boosters, but are now being marketed specifically as prebiotics for “intestinal health.” Some yogurts contain both probiotics and prebiotics, a kind of one-two punch. Prebiotics are also added to some cereals and juices and other foods. Both probiotics and prebiotics are available as dietary supplements.

Living up to their health claims?

Like probiotics, prebiotics alter the balance of bacteria in the intestines, and many proposed health benefits for prebiotics are thus similar to those made for probiotics. Though most studies have been in animals and test tubes, there’s some evidence that prebiotics may reduce inflammation associated with some bowel diseases (such as Crohn’s disease and ulcerative colitis), help alleviate constipation, improve cholesterol and triglyceride levels, inhibit development of colon cancer, and have favorable effects on the immune system, among other benefits. Some studies in people show that prebiotics enhance calcium and magnesium absorption, which might help keep bones strong.

Bottom line

Prebiotics look promising, but will consuming them in foods or capsules make a notable difference to your health? No one can say. It’s unknown which kinds of prebiotics may be best for which conditions. And even if the optimal dose were known, foods usually don’t say how much they contain, and supplements are not well regulated, so their labels may not be accurate. Moreover, not everyone will respond the same way to a given dose of prebiotics—much depends on the bacteria you have to begin with, as well as other differences. At the very least, yogurt with added inulin provides some fiber and may boost calcium somewhat. Large amounts of prebiotics may cause abdominal pain, flatulence, bloating, even diarrhea, though. We don’t recommend prebiotic supplements.

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