It sounds downright risky, but snacking on billions of live bacteria can actually improve digestion, support the immune system and bolster overall health.
Called probiotics, these "friendly" microbes with health benefits are found naturally in breast milk and fermented foods such as yogurt, kefir, aged cheese, miso and certain pickles and sauerkraut. They work by keeping intestinal flora balanced and preventing not-so-friendly bacteria from taking over and causing disease.
But during the past 50 years, the increased use of antibiotics and a changing diet low in soluble fiber and high in refined carbohydrates have produced an "invisible epidemic of insufficient probiotics," said Gary Huffnagle, professor of internal medicine and microbiology at the University of Michigan Medical School. "We're not getting what we used to [through diet], and we're destroying what's there," he said. "As a result, the balance of our intestinal microbe population has changed, sometimes with disastrous effects on our immune system."
Research on the topic is exploding. The National Institutes of Health recently announced that it will explore how bacteria in the body can promote health, and the food, supplement and cosmetics industries aren't about to be left behind. Though Americans are notorious germ freaks, the helpful bacteria and yeasts are being added to beverages, cereals, wellness bars, pet foods, infant formula and even personal-care products. As supplements, probiotics can be purchased as pills, liquids, capsules and powders.
The worldwide probiotic yogurt category alone is expected to increase in sales to $500 million from $294 million by 2010, according to the market research firm Euromonitor International.
But finding the correct type of probiotic food or supplement can be daunting for consumers, especially because research is evolving, and many functional foods make unproven claims.
Only a few bacteria (members of the lactobacillus and bifidobacterium genuses) have been studied extensively, and scientists are still trying to figure out which bacterial strains are most effective for particular problems.
While the strain Lactobacillus rhamnosus GR-1 has been shown to help with vaginal yeast or urinary-tract infections, Sacharomyces boulardii lyo has a positive effect on diarrhea and inflammatory bowel disease.
Another research focus is "figuring how we detect an 'imbalance' in a single human being," Huffnagle said. "When we look at groups of people, we can make generalizations, but for any single person, the generalization may not hold true."
Meanwhile, the marketplace is a free-for-all. All products labeled "probiotic" should contain "live" material, but some don't; others don't contain enough.
When the testing service Consumerlab.com looked at 13 products, it found that only eight contained at least 1 billion organisms in a daily serving, the generally recommended minimum dose.
But even the proper minimum dose isn't really known. Some products have been shown to be effective at 100 million live cells, others show positive results at 1 trillion.
Still, "the potential of probiotics to improve health rivals drugs in terms of impact," said Huffnagle, author of The Probiotics Revolution, who says probiotics are more than beneficial; they're essential and deserve their own food group.
"We have 2.5 pounds of microbes inside us," he said. "The medical revelation is that when they cooperate and work together, they function in our body like an organ. Microbes in our digestive tract have profound effects on our health."
One of the most promising treatments uses probiotics to replenish the "good" bacteria and prevent or ease the symptoms of antibiotic-caused diarrhea, a growing problem for hospitals because of antibiotic resistance.
Although antibiotics can be lifesaving drugs, they work by killing many bacteria in our microflora, including the beneficial ones. Failure to restore the good bacteria can cause side effects.
But mounting research, including a recent study published in the British Medical Journal that looked at the strains used in Dannon's DanActive, have shown that probiotics can counter the side effects.
Though not a routine practice in most hospitals, the National Jewish Medical and Research Center gives probiotics to almost all of the infectious-disease patients who receive antibiotics.
For the past two years, Helen DeVos Children's Hospital in Grand Rapids, Mich., has used them to improve the intestinal health of premature infants.
And pediatricians are increasingly recommending them for their young patients.
"They worked well," said Chicago's Wendy Burgess, whose 2-year-old son, Henry, had diarrhea after a round of antibiotics for an ear infection. Burgess' doctor suggested Florastor, which contains the probiotic yeast Saccharomyces boulardii lyo. "I didn't know what probiotics were, but if he were to go back on antibiotics, I'd start them to be proactive," she said.
Julie Deardorff writes for the Chicago Tribune.