Myth of Probiotics

The human body contains 10 times as many bacterial cells as human cells. Most are benign or contained, but about a third are helpful, or what are called "friendly bacteria." The term "probiotics" refers to live organisms that naturally exist in the human gut and are reintroduced, usually orally, to increase the proportion of friendly bacteria in the gut. Some products, particularly yogurt, are marketed as promoting digestive health by reintroducing probiotics.

Contradictions Abound

Since the study of probiotics is young, marketing claims by supplement companies have far outrun the rate at which these products are tested. Consumers may find the information available bewildering. For example, one expert claims that stomach acid kills 99.9 percent of lactobacillus and bifidobacteria, which are probiotics in yogurt. Another says these probiotics are among the few that do survive the stomach. Then a UCSF study finds probiotics that don't even need to be alive to have an effect, since they have an immunostimulative role (like dead viruses used for a vaccine).

As another example, one expert argues that probiotics need a protective coating before they're ingested. Another claims that could kill the bacteria, while a third says no coating is needed at all. "I don't know how to tell consumers to sort through it," says Mary Ellen Sanders, executive director of the International Scientific Association for Probiotics and Prebiotics, as reported in the Los Angeles Times.

What the Science Says

The National Center for Complementary and Alternative Medicine (NCCAM) sponsored a colloquium in November 2005. The findings were mixed. The greatest support of the effectiveness of probiotics was in the treatment of diarrhea, especially if caused by rotavirus, the leading cause of infantile diarrhea.

Other Encouraging Applications

The symposium also found that probiotics could prevent and treat urinary tract infections. They also appear to reduce recurrence of bladder cancer and to provide effective treatment for irritable bowel syndrome (IBS), one of the most common uses of probiotics. Evidence suggests that probiotics can shorten an intestinal infection caused by the bacterium Clostridium difficile, and prevent and treat pouchitis (a condition that can follow surgery to remove the colon) and atopic dermatitis (eczema) in children.

Room for Improvement

The conference panel found, however, that despite the encouraging evidence in certain applications, the benefits of probiotics were usually low. They also noted that much perceived success derived from a strong placebo effect.

Many gaps in the research were pointed out as targets for further study, such as the molecular process by which probiotics take effect. The panel also identified a need for larger, better-controlled studies. Furthermore, proper doses must be established that will survive stomach acid without being toxic. Schedules also need to be established; for example, to account for interaction with food and the merit of an empty stomach to avoid stomach acid.

IBS

IBS has many causes, but a common theme is that food isn't fully digested, giving gas-producing bacteria in the gut more food of its own. While adding friendly bacteria may help crowd out the bad bacteria, a more effective solution may be to make sure food is properly digested. This includes eliminating foods to which one is allergic, and combining foods digested at certain pH levels. For example, meats and fibrous vegetables shouldn't be eaten with starchy vegetables and grain, and fruit should be eaten separately altogether. Water should be consumed mostly between meals to avoid watering down stomach acid. Sometimes, insufficiently tested products provide an inadequate substitute for good habits.