Supermarkets are now brimming with new kinds of yogurt, as well as drinks and cereals, that contain health-promoting bacteria or yeast called probiotics. Long popular in Europe, probiotics are just starting to take off here.
On the shelves: Dannon Activia, Dannon DanActive Immunity, Lifeway Kefir, Kashi Vive Probiotic Digestive Wellness Cereal, Stonyfield Farm yogurt/smoothies, GT's Organic Raw Kombucha tea.
Claims: Digestive balance, digestive regularity, immune system support, healthier skin and hair, decreased appetite, prevention of vaginal infections, cholesterol lowering, cancer protection.
Evidence: Microbiologists agree that the potential benefits of probiotics are enormous, but as a group of experts reported at an international conference a little over a year ago, consumers usually have no way of knowing what they're getting in the new products. "There are many different strains of probiotics, but only a few have been studied and shown to have a distinct benefit," says Mary Ellen Sanders, Ph.D., executive director of the International Scientific Association for Probiotics and Prebiotics. "Also," she adds, "products are often labeled inadequately. They may not tell you the strain of probiotic or the levels present through the end of a product's shelf life."
Nonetheless, there's definite promise. Several studies have shown that Dannon's Activia speeds intestinal transit time the hours it takes food to pass through your digestive system which may help if you have a problem with constipation.
Companies also claim that probiotics boost immunity. In one study, people who ate DanActive had shorter-lasting colds. Other research, in Sweden, showed that a certain strain of bacteria cut the number of sick days that employees took. But that study, like most others with probiotics, was conducted with supplements, not with commercially available foods, which don't contain enough of the strain in question.
There is also strong evidence supporting claims that three strains of probiotics Bifidobacterium lactis, Saccharomyces boulardii, and Lactobacillus rhamnosus GG relieve or prevent diarrhea. But again, you won't find enough of these microbes in any supermarket foods; you'd need to buy probiotic supplements such as Florastor (which contains Saccharomyces boulardii) or Culturelle (Lactobacillus rhamnosus GG) in a health food store.
Shopping advice: If your goal is to just get some potentially beneficial bacteria into your diet, use products that contain Bifidobacteria and Lactobacilli. But you can hedge your bets still further by choosing items that would be good for you even if they didn't tout probiotics. Kashi's Vive Probiotic cereal is high in fiber. The yogurt, smoothies, and kefir drinks from Dannon, Stonyfield Farm, and Lifeway all deliver calcium and protein. Stonyfield and Lifeway also include inulin, a naturally occurring fiber that boosts your body's absorption of calcium, report several studies.
Watch out for: Promises of weight loss, improved liver function, healthy skin, or cancer-fighting properties there's no substantial research to back up these claims.