"We are more “bacterial” than “human”: bacteria outnumber our own cells by 10:1."

At first, it seems alarming that Canadian physician Gregor Reid is trying to spread bacteria to as many people as possible. America, after all, seems to be waging war on germs. Doctors and advertisers and politicians tell us that antibiotics are helpful for minor illnesses, that no soap is sufficient unless it is “antibacterial,” and that Lysol has been “keeping America germ-free for over 100 years.” Since the discovery of penicillin, the medical community has devoted tremendous energy and resources toward efficiently eliminating bacteria. However, the rapidly expanding field of probiotics – the science of useful bacteria – is beginning to demonstrate the vital role that bacteria play in the health and proper functioning of the human body. Scientists studying probiotics believe that health may be improved not only by ridding our bodies of harmful bacteria, but also by actively importing other bacterial strains. Probiotics are now thought to be useful in preventing and treating a wide range of illnesses, including cancer and HIV.

Bacteria have not gotten the credit they deserve. Pathogenic strains are few and far between, and a plethora of harmless and even beneficial bacteria colonize parts of the body like the skin and the digestive system. If we were to count the cells in our bodies, we would find that we are more “bacterial” than “human”: in fact, bacteria outnumber our own cells by a ratio of ten to one. While these bacteria do live off our bodies, the relationship is not parasitic, but rather symbiotic.

Evidence in favor of probiotics began to appear in 1973, when a study by Dr. Andrew Bruce noted a reduced rate of infection in women whose vaginal tracts were colonized by members of the Lactobacillus family of bacteria. Since then, biologists have produced a wealth of conclusive data regarding the benefits of probiotics. Gut-colonizing bacteria, for example, have shown a remarkable ability to combat illness. Studies have shown that dietary supplements of the probiotic L. reuteri significantly reduce both the incidence and the duration of diarrhea in children. L. reuteri also protects against poisoning caused by gut pathogens such as Salmonella and E. Coli. The probiotic L. johnsonii has been shown to fight infection by the ulcer-causing bacterium Helicobacter pylori.

In addition, probiotics such as L. bulgaricus can help lactose-intolerant individuals to metabolize lactose, reducing the severity of their disorder and helping them to obtain important nutrients found in dairy products. Studies also have linked the colonization of the mouth by several probiotic strains with reduced levels of tooth decay.

Further evidence suggests that probiotics can reduce the incidence of allergic conditions, apparently because these beneficial bacteria expose the body to antigens, familiarizing it with chemicals that would otherwise cause severe reactions. For example, infants supplemented with L. rhamnosus run a much smaller risk of developing atopic eczema, a skin allergy.

Probiotics may also play a future role in cancer prevention. Not only do some bacteria seem to metabolize harmful chemical carcinogens into benign compounds, others are thought to synthesize chemicals that actively block the growth of cancer cells. In studies performed on rats with chemically-induced cancer, those with probiotic-supplemented diets had a lower prevalence of tumors.