As with high fashion and Clive Owen, Europeans were onto this practice long before we were. Around 1900, Elie Metchnikoff, Ph.D., a Nobel Prizewinning Russian researcher, noticed something peculiar: Yogurt-loving Bulgarians were living as long as 100 years. The process of fermenting dairy products to create yogurt (and its cousin, the fermented milk drink kefir) involves adding live bacteria. Metchnikoff concluded that those bacteria were responsible for Bulgarians' extended lifespan. Europeans and Asians began enthusiastically eating the stuff, but Americans are just now catching on, thanks to a recent boom in probiotics research and yogurt nutrition. "The immune system and digestive tract are so complex that we are just beginning to understand how probiotics work in the body," says Mary Ellen Sanders, Ph.D., executive director of the International Scientific Association for Probiotics and Prebiotics.
The Good, the Bad, and the Nasty
Here's what we do know. Your digestive system is like Casablanca for microorganisms: Some 400 species of bacteria and yeast can be found there. Some are locals, created by your body; others are tourists, just visiting after you ingest them via food. Of these microorganisms, those like salmonella and some species of E. coli are nasty (usually the tourists, naturally). And others like L. casei and L. reuteri can be nice — very nice. "Probiotics are basically any microorganism that, when ingested, may benefit human health," says Athos Bousvaros, M.D., a specialist in gastroenterology and nutrition at Children's Hospital Boston.
According to Dr. Bousvaros, your digestive tract houses much of your immune system, a complex constellation of cells and tissues that fight pathogenic organisms that can make you sick. Having more of the beneficial organisms there may help prevent illness: They protect you both by stunting the growth of the nasty ones on the spot and by forcing them out, essentially taking all the free seats in the digestive tract; the bad guys just have to move on, ultimately exiting your system. When the number of good bugs drops — for example, after a course of antibiotics, which kills many of the good guys as well as the bad — you might be more likely to get sick. And as you age, your natural levels of beneficial bacteria decrease. But swallowing 'em can help get you healthy, plus stop trouble before it starts.
Probiotics give your immune system a boost. New research shows that L. reuteri can help you kick the Kleenex while your colleagues sniffle. A study in Sweden found that workers taking the probiotics were healthier than the pla — cebo group, who called in sick two and half times more. "L. reuteri helps keep you healthy by secreting reuterin, an antimicrobial agent that prevents the growth of pathogenic microorganisms in the gut," says Vicki Koenig, R.D.
They fight itch below the belt. Yeast and bacteria are like the Sharks and the Jets of your body. When you have similar amounts of both, they mind their own business — sort of a microorganism cease-fire. But when the balance is upset, yeast can run rampant, leaving you with an itchy infection. "Probiotics keep the yeast population down by crowding them out and competing for the same food," Koenig says. The traditional remedy is yogurt — but you've got to eat it, not smear it on. "If inserted vaginally, the milk sugar in yogurt can feed the yeast, making the infection worse," she warns.
They keep you moving. European women have long used probiotics to stay regular, and research seems to be backing them up (or not, so to speak). "Probiotics produce short-chain fatty acids in the colon that can help retain moisture and result in softer stools," Sanders says. Studies conducted at the Georges Pompidou European Hospital in Paris found that subjects moved their bowels in less time (which is good, since slow bowels can lead to health problems) when eating yogurt containing the probiotic B. animalis daily. "They saw results within 2 weeks of starting the probiotic treatment," says Philippe Marteau, M.D., lead researcher and head of gastroenterology at the Lariboisire Hospital in Paris.
They reduce gas emissions. Most lactose-intolerant people see dairy and think farting and bloating. But it turns out that in dairy foods with live active bacteria, the probiotics used for fermentation produce lactase, an enzyme that digests lactose before it reaches the colon and stirs up trouble. A study in the Journal of the American Dietetic Association found that kefir improved lactose digestion and reduced gas in the lactose intolerant.
Where the Bugs Are
So how do you tap into these little monsters' power? There are no government recommendations for how many — or what kinds — of probiotics you should gulp down. So it's up to you to do a little research. "Just as different vitamins have different effects, the various probiotic strains impart different health benefits," Sanders says. (See "Bugs to the Rescue") The no-brainer approach is a daily cup of yogurt. Depending on the brand, it contains most of the good bacteria you need. "With yogurt, you also get the benefits of nutrients such as calcium, riboflavin, and vitamin B12," says Densie Webb, Ph.D., R.D., coauthor of The Dish: On Eating Healthy and Being Fabulous!
If you're sick of yogurt, consider trying a supplement or one of the new products with added probiotics. As more manufacturers pile on the healthy-gut bandwagon, the market for probiotic ingredients is expected nearly to triple by 2010, according to Frost & Sullivan, a London-based consulting firm. Many of the new items are still in the dairy aisle in smoothie form like Yakult from Japan. But probiotics are popping up in unrefrigerated foods too, such as Kashi Vive cereal and Attune bars. They taste pretty good, but research hasn't yet determined whether they work as well as yogurt (though the outlook is good).
As for pills, "no studies have shown that probiotics in a food are more effective than in a supplement," Dr. Bousvaros says. Look for a brand that specifies on its label the viable dose of live bacteria or yeast — which varies by strain but is often between 1 billion and 10 billion — through its shelf life, like Culturelle or Florastor.
Does booze have similar benefits? The jury's still out, but research suggests red wine and dark beer may have probiotic effects. So have a glass — right after your yogurt — and celebrate your health.