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Should Probiotics Be Part of Your Diet?

Researchers have high hopes for foods and supplements containing 'good' bacteria

By Maureen Callahan | November 20, 2012
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Maureen Callahan is a registered dietitian, recipe developer and lead author of the Health.com diet book review series.

As we grow into middle age and beyond, we tend to spend more time managing our gut. An infection, a course of antibiotics or garden variety stress can all upset the delicate balance of "good" and "bad" bacteria in our digestive system, potentially causing illness or disrupting our immune function.

A popular theory is that we can restore the right balance with certain foods or supplements containing "good" bacteria, or probiotics (pro and biota translate as "for life"). The digestive tract, part of your immune system, can then return to combating ailments and illness causing pathogens.

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Probiotics may also have the potential to do much more. New studies suggest that these microorganisms can help with everything from fighting the common cold to lowering cholesterol levels and possibly even managing such conditions as heart disease, diabetes, obesity and anxiety.

What We've Learned About Probiotics

One expert compares the study of our human microflora to examining the oceans — both are wide, deep and largely unknown to us. About 100 trillion microbes make their home in (and on) the typical adult body — approximate weight: three pounds — so teasing out which specific strains of "good" bacteria can address which ailments is a huge undertaking. Even if we knew, we'd have to find a way to determine whether the "good" bacteria found in most digestive tracts is doing its job. And when devising treatments, we need to be sure that promoting the production of "good" bacteria over "bad" won't have unanticipated negative side effects.

A multimillion-dollar research effort by the National Institutes of Health hopes to sort out some of these questions. Human Microbiome Project scientists are working to identify the various microbial communities harbored by the body, like those in the nose, mouth and gastrointestinal tract. The researchers also want to discover the DNA footprint of the microorganisms and map out how they function in relation to health and disease.

It could take years before the team has unraveled enough genetic data to make any specific recommendations. When the project's initial findings were released this summer, NIH director Francis Collins compared its scientists to "15th-century explorers describing the outline of a new continent," and said their work would eventually form "the foundation for accelerating infectious disease research."

Early findings point to the health benefits of "good" bugs being strain-specific. In other words, all probiotic bacteria are not the same — and some may be useless in addressing any individual's health condition. Preliminary studies are beginning to identify a few effective potential treatments, though.

Research presented at the American Heart Association’s recent scientific session found that a strain of bacteria called lactobacillus reuteri (not yet available in consumer products) can dramatically lower levels of total cholesterol, specifically the "bad" LDL. A separate study showed that a combination of two bacterial strains, LGG and BB12, could help shorten the duration and severity of the common cold. It's a combination already found in some yogurts and over-the-counter supplements.

How Can Probiotics Help You Now?

Researchers can envision a time when probiotic treatments are the cornerstone of medicine. For example, doctors could analyze a child's biome at birth, track its development, analyze the conditions to which it leaves the child vulnerable and prescribe specific cocktails of probiotics to increase the internal production of microbes that will successfully combat those ailments.

Until that day arrives, how can you tap into probiotic health benefits? Many experts support the food-as-medicine approach. They believe fermented foods rich in "good" bacteria — like buttermilk, sauerkraut, kimchi, miso, kefir and yogurt — are safe, natural sources of probiotics. They also have the added bonus of delivering a variety of other vital nutrients. (Learn more about probiotics in yogurt from NPR.)

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When it comes probiotic supplements, however, the scientific community is less convinced. There are questions about whether the probiotic strains in supplements can survive the stomach's acidic environment. Even if they can, many researchers question whether the strains can provide the benefits their makers promise.

Remember: Supplements don’t have to undergo the same rigorous safety and efficacy testing as drugs. It's best to talk with your doctor or a health professional familiar with probiotics about what foods or supplements, if any, they recommend.

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Whatever route you take, you'll likely get better results by combining your probiotic choices with "prebiotic"-rich foods like garlic, onions, leeks, bananas, artichokes and barley. Prebiotic fibers are nondigestable carbohydrates that stimulate the growth of probiotics. Fermented by the colon, prebiotic fibers also improve the pH of the digestive tract and help combat pathogens.