Probiotics: The Friendly Bacteria

These little buggers are credited with easing tummy trouble, eczema, and more. But do they live up to the hype?
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A few years ago, my son received a microscope for his birthday. We put everything we could think of on those little glass slides -- blades of grass, dog hair, even a drop of saliva -- so we could peek at the inner workings. But the most fascinating, by far, was yogurt. Just one little dab of the stuff revealed hundreds of tiny quivering, living organisms.

Sound gross? I've got news for you. Lots of foods you eat are alive. Yogurt is the most common, but buttermilk, ice cream, juice, cheese, granola bars, cereals, baby formula, and even pizza can now contain probiotics, also known as the "good" bacteria that my son and I saw under the microscope. While scouring the grocery store shelves, you've probably noticed all the new probiotics products being marketed to kids, along with claims about what each can do: Improves immunity! Prevents diarrhea! Helps calm colic! In fact, the widely accepted definition of probiotics is "live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host." And as you'll see, there is evidence that probiotics can play a role in improving colic, eczema, and intestinal problems. But can they really make your child healthier? That's the $2 billion question, the amount the U.S. probiotic market is projected to be worth in 2013.

Let's start with a mini biology lesson: Trillions of bacteria already live in your child's (and your own) gastrointestinal system, many of which are considered to be good because they help keep him healthy. They've been there since birth, when your baby's GI tract became colonized with good, bad, and benign bacteria (known as flora) as he passed through the birth canal and picked up some of your microbes. Because babies delivered by C-section miss out on this, they initially end up with a different collection of flora, explains Mary Ellen Sanders, Ph.D., a microbiologist and the executive director of the International Scientific Association for Probiotics and Prebiotics. (Scientists suspect that this difference in colonization may be behind the higher incidence of allergies and asthma in C-section babies, but more research is needed.)

If you nurse, you help your baby build up more good bacteria, because breast milk contains substances known as prebiotics that promote the growth of healthy bugs. They supply nutrients to the living bacteria and enhance their ability to survive and thrive in your child's gut. "By shaping the content of an infant's gastrointestinal tract, breast milk also helps 'educate' the developing immune system," says David Mills, Ph.D., a University of California, Davis microbiologist. (Prebiotics are also found in high-fiber foods like whole grains, fruits, and vegetables.) Once your child weans and starts on solid foods, his gut microflora will change, and then remain pretty much constant throughout his or her lifetime.

But there are outside forces that may throw off the balance. Antibiotics, for instance, can kill both bad and good bacteria in your child's gut flora -- and that can lead to gastrointestinal distress. "About 20 to 30 percent of kids develop diarrhea when they take antibiotics," says Daniel Merenstein, M.D., director of research in the department of family medicine at Georgetown University Medical Center, in Washington, D.C. Various diseases, too, can disturb this otherwise fixed amount of microflora.

Some research has shown that consuming probiotics through foods or supplements can positively affect your child's balance of bacteria, and consequently, his health. We talked to the top probiotic researchers to find out more, and this is what we learned.

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