Do probiotics really work?

By: EatingWell Editors

Pictured Recipe: Tutti-Frutti Muesli

Probiotics are “friendly” bacteria found in the gut that help us digest foods and fight harmful bacteria. They also include live, active cultures used to ferment foods like yogurt and sauerkraut. Reputed to improve digestion and boost immunity, foods that contain probiotics have been appearing more and more on supermarket shelves. First came yogurt enhanced with special probiotic strains. But the trend has spread quickly, and now cottage cheese, energy drinks, snack bars and cereals advertise high levels of beneficial bacteria too.

The good news is that advances in food processing make it likely that probiotics get to the gut where they can tip the balance of bacteria in a healthy direction. “Companies have developed technologies that allow bacteria to resist the temperatures and pressures of manufacturing as well as the heat and acidity in the stomach,” says Ralph Felder, M.D., Ph.D., author of just-out The Bonus Years Diet (Putnam).

The bad news is that there are thousands of probiotic strains; only a handful have been clinically tested. Manufacturers don’t always list the strain, or amount, of bacteria added. Plus, individuals respond differently to various strains, so what works for one person may not work for another, says Jeannie Moloo, Ph.D., R.D., spokesperson for the American Dietetic Association.

If you’d like to try probiotic products, your best bet is yogurt with a “Live & Active Cultures” seal (regulated by the National Yogurt Association), which marks a product that meets a specified level of “friendly” bacteria. The absence of a seal doesn’t mean a probiotic-enhanced food is ineffective (only yogurts are eligible), and often it pays to test several. “If one isn’t providing benefits after a couple of weeks, try another,” suggests Moloo.

Related: 7 Must-Eat Fermented Foods for a Healthy Gut