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Probiotics: The Friendly Bacteria

Even as you read this, a science experiment is taking place in your digestive tract. More than 5,000 strains of bacteria are growing in there, far outnumbering all the cells in your body. Feeling a bit queasy? Relax. These bugs come in peace. "They help stimulate your immune system, promote healthy digestion, and may reduce gas and bloating," says Sherwood Gorbach, M.D., a professor of public health and medicine at Tufts University. "In addition, the good gut flora crowds out microorganisms like yeasts, viruses, and bacteria that trigger illnesses and disease."

Lately, food companies have begun adding these bacteria, known as probiotics, to their products. Should you buy into the hype? We got experts to weigh in.

Q.If I already have good bacteria in my body, why do I need more?

A.Stress, preservatives, and antibiotics are among the many things that can kill the beneficial bugs in your system, says John R. Taylor, N.D., author of The Wonder of Probiotics. In fact, Stanford University researchers found that people who took a five-day course of antibiotics reduced the disease-fighting strains in their system by 30 percent. While these levels typically return to normal, even a brief decline can allow harmful microorganisms to thrive. "As a result, you can get yeast or urinary tract infections or diarrhea," says Taylor. "If you already have an irritable bowel disease, a dip in good bacteria could cause it to flare up. Increasing your intake of probiotics, however, may counter these effects, finds a study from the Tufts University School of Medicine. Additional research shows that probiotics may also help fight obesity and reduce your cancer risk.

Q. Do I need to buy specialty foods to get probiotics?

A. Not necessarily. Small amounts of good bacteria can be found in fermented foods, like yogurt, kefir, sauerkraut, miso, and tempeh. And while trying one of the new fortified foods—everything from orange juice and cereal to pizza and chocolate bars—may sound more appetizing than, say, spooning up sauerkraut, keep in mind that not all of these options offer the same probiotic effects. "Cultured dairy products, like yogurt, provide a cool, moist environment for bacteria to thrive in," says Gorbach. "But most strains don’t live as long when added to dry goods." To make sure you’re getting the hardiest forms, look for a product with bifidobacterium, lactobacillus GG (LGG), or L. reuteri on its ingredients panel.

Q. Can I take a probiotic supplement instead of changing my diet?

A. Yes—you’ll get more bacteria from most capsules, powders, and pills than you will from a container of yogurt. Plus, popping a supplement while taking antibiotics may help lower your risk for side effects, like diarrhea, by 52 percent, finds a Yeshiva University study. Other research shows supplements may reduce the duration and severity of a cold. Look for one that contains 10 to 20 billion colony-forming units (CFUs), and read the label to learn how it should be stored.