Probiotics are the latest craze in the food industry, turning up in everything from pizza to chocolate. They now tally $20 billion in global sales, expanding at 20 to 30% a year. If you're not already consuming them in some form, chances are you will be soon.
"Probiotics are the new vitamins," says Shekhar Challa, MD, a gastroenterologist in Topeka, KS, and the author of Probiotics for Dummies. That's a bold statement, because probiotics are actually live microbes—specifically, beneficial bacteria that promote human health if consumed in large enough quantities. For germophobic Americans, it's a revolutionary concept. But the 100 trillion microbes that live in your large intestine do dozens of good things for you. They process indigestible fibers and help keep bowel function regular. They produce a number of vitamins, including B6, B12, and K2, and aid in the absorption of minerals such as iron, calcium, and magnesium. Equally important, they help fend off bad bacteria such as Salmonella and E. coli, which can cause diarrhea and, in extreme cases, severe anemia, kidney failure, and death.
"The intestines are a war zone, where beneficial and harmful bacteria are fighting to establish predominance," says Venket Rao, PhD, emeritus professor of nutritional sciences at the University of Toronto. The key is for the good guys to outnumber the bad. If you want to give them a competitive edge, a regular supply of probiotics can help.
The payoff can extend well beyond your gut, and your immune system is a prime beneficiary. In a Swedish study of 262 workers, those who took probiotics for 80 days were 42% less likely to take a sick day for an upper respiratory infection or gastrointestinal disease. Regular doses can help reduce vaginal and urinary tract infections. If you're prone to allergies or eczema, probiotics may even help tamp down an overactive immune system. They accomplish all this by producing their own form of antibiotics, blocking pathogens from adhering to the gut, and spurring production of chemical messengers called cytokines, which communicate with the immune system throughout the body. Probiotics may even enhance your mood, thanks to a similar cross talk with the central nervous system.
So the conclusion is simple, right? Take probiotics. Unfortunately, it's not that easy. There are more than 3,000 species of good bacteria in your gut, and each has its own talents. The cultures you're consuming may not be the ones that reduce colds or fight diarrhea. And they have to be handled correctly, so they aren't killed during processing or storage. "No more than 10% of products that claim to be probiotic have been proven in human trials," says Gregor Reid, PhD, chair of human microbiology and probiotics at the Lawson Health Research Institute.
So what's a shopper to do?