ProbioticsNew Research Directions

Eating live bacteria might sound like the latest in extreme cuisine. But probiotics— “good” or “friendly” bacteria—in foods such as yogurt not only taste good but also are good for you.

“Many types of bacteria reside in our digestive tracts,” explains Joy Dubost, PhD, RD, a Washington,D.C.-based spokesperson for the Academy of Nutrition and Dietetics (formerly known as the American Dietetic Association). “They’re necessary for proper bodily function—everything from digesting foods to keeping the gastrointestinal tract healthy.”

Probiotics are healthful microorganisms that work in concert with the naturally occurring gut flora to keep harmful bacteria and certain health problems at bay.

One of the biggest challenges in researching probiotics is that no one type of bacteria cures all ills or even works in the same way as another. That’s because there are many different strains of probiotic bacteria. Think of it as family and extended family: Just because your brother is a brain surgeon doesn’t mean your plumber uncle can double for him in the operating suite.

In the probiotic world, some strains of bacteria have proved valuable in speeding the movement of food through the intestinal tract and thus alleviating constipation. Other strains have been studied for their help in relieving the type of diarrhea that comes with antibiotic use, lessening the gas and bloating of lactose intolerance, and easing the symptoms of irritable bowel syndrome and inflammatory bowel disease.

“Scientific research into the potential of probiotics to prevent and treat a number of other diseases is early but is moving quickly,” says Dubost. “However, two emerging areas are obesity and allergies.”

Healthy gut flora can reduce the risk of obesity, while poor gut flora can trigger weight gain. That’s the bottom line of a study published in the September 2011 British Journal of Nutrition. Swedish scientists fed a probiotic bacteria called Lactobacilli plantarum to one group of rats and added E. coli (not the kind associated with undercooked beef) to the drinking water of a second group of rats. Results revealed that rats consuming the probiotic bacteria from birth to adulthood not only had a higher proportion of good bacteria in their gut but also gained significantly less weight than rats fed E. coli, even though both groups ate the same high-energy diet.

Probiotics have also been linked with preventing childhood obesity. In a study published in the October 2011 issue of the International Journal of Obesity, Finnish researchers fed 159 pregnant women a strain of Lactobacillus rhamnosus from four weeks before delivery to six months afterward. They then took weight measurements of the babies at regular intervals from the ages of 3 months to 10 years. Results showed that those children whose mothers consumed the probiotics experienced a less excessive weight gain during the first few years of their lives.

When it comes to allergies, daily consumption of probiotic yogurt could be a boon to those who suffer with upper respiratory problems during pollen season. According to an article published in the April 2011 issue of Clinical & Experimental Allergy, 31 adult volunteers fed yogurt with Lactobacillus paracasei for four weeks experienced significantly less congestion in response to exposure to grass.

The newest directions in probiotic research pertain to type 1 diabetes mellitus, cholesterol levels, immune system function, oral health, and even aging. For example, studies show that dietary changes, the diagnosis of chronic diseases, and the corresponding use of medication can change older adults’ gut flora and that the addition of probiotic foods can correct the friendly-unfriendly bacterial imbalance and improve health.

There are a number of products on supermarket shelves even though the advantages of probiotics are still under study. That poses a quandary for consumers trying to choose, says Dubost. “The Food and Drug Administration hasn’t approved health claims for probiotics, so consumers can’t look for this type of labeling on products at the store. Instead, I suggest buying probiotic products made by a company that documents its research and offers its research for public review,” she says.

Fermented dairy foods such as yogurt are among the best sources of probiotics. Products that contain at least 100 million live cultures per gram are labeled with the Live & Active Cultures seal established by the National Yogurt Association, namely the beneficial bacteria Lactobacillus bulgaricus and Streptococcus thermophilus.

“Still unanswered is how much of a dose and which strains of probiotic bacteria are optimal,” says Dubost. “But we do know it’s important to take probiotics on a consistent and regular basis. You can’t just eat one serving and look for an effect. It’s all about changing the microflora of the gut.”