"Healthy bacterial colonization of the vagina raises its acidity, creating an unfavorable environment for HIV and other pathogens."
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One of the most important functions of gut-colonizing probiotics is their regulation of the immune system. Dr. Walter Dobrogosz, formerly of North Carolina State University, explains, “You want the body to fight off invaders using potent chemicals and an inflammatory response. But you don’t want to overdo it.” Recent research by Dr. Ruslan Medzhitov at Yale has shown how bacteria can send signals to our immune systems through “toll-like” receptors on the surface of white blood cells and the inside of the intestine. In this way, bacteria can elicit immune responses when necessary, as well as down-regulate the excessive inflammation that can cause conditions such as ulcerative colitis and Crohn’s disease. “Crohn’s disease is an example of a pathology caused by an unregulated response,” says Dobrogosz. He points to the effect of probiotics on Crohn’s disease as evidence that they can help to prevent auto-immune disorders.
Though most probiotics occur naturally in the human body, not all individuals possess them. Helpful bacteria may not adequately colonize children who do not breast-feed or eat other fermented dairy products. Also, overuse of antibiotics can have unintended consequences, affecting our helpful resident probiotics as well. Increasingly, scientists and doctors believe it may be necessary to incorporate probiotics into our diets, and many probiotics are already available on the market as dietary supplements.
However, Dr. Gregor Reid of the University of Western Ontario, an outspoken advocate of probiotics, warns that not all such products may be healthful: “There are a lot of companies carrying stuff, calling it probiotics, and it’s not probiotics,” he cautions. Reid explains that many products contain an insufficient concentration of organisms, or even none at all, and that some contain dangerous contaminants. “Sadly, this hurts the whole field,” laments Reid. He worries that physicians, the most important allies in the promotion of any health-related product, will become suspicious of all probiotics as a result of some fraudulent products.
Other barriers exist to the widespread acceptance and use of probiotics. Commercial sales are picking up in Japan and Western Europe, but the United States lags behind. “Education is a big, big thing,” emphasizes Reid; Americans will not want to take probiotics before they have been shown evidence of its benefits. Still, Reid remains optimistic, pointing out that “we take vitamin C without blinking, and I see the same for probiotics.”
Reid believes that probiotics may do their greatest good in the developing world, where diarrhea, intestinal parasitic infections, and vaginal infections – the very diseases that probiotics have been shown to prevent – are rampant. Dobrogosz agrees: “in the developing world, 90 percent of the poor have H. pylori infections. Probiotics could be a tremendous help.”
Perhaps the most exciting possibility for probiotic medicine is Dr. Reid’s research on using probiotics to reduce the spread of HIV. His work supports the hypothesis that healthy bacterial colonization of the vagina raises its acidity, creating an unfavorable environment for HIV and other pathogens. He has worked with the international program “Western Heads East,” based at the University of Western Ontario, which plans to show Tanzanians how to add probiotic cultures to yogurt during its fermentation.
The field of probiotics offers a challenging new perspective on the role of bacteria in human health. “Bacteria are not only pathogens, as the biomedical community thought for a long time,” notes Dobrogosz. Indeed, symbiotic bacteria play such an integral role in our bodies that we can hardly think of them as separate organisms. According to Reid, the question is no longer how we should kill them, but rather “how we should nurture them, how we should feed them, because they are ours. They are part of us.”
Aaron Mitchell is a senior in Jonathan Edwards College.
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