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Bacteria to the rescue: Indiscriminately killing germs eliminates the ones that are helping us Add to ...

Microbes cause infections, bad breath, body odour, intestinal gas and an array of embarrassing and unfortunate conditions. But they may also turn out to be the best remedy, explains Toronto microbiologist Jason Tetro in his new book, The Germ Files: The Surprising Ways Microbes Can Improve Your Health and Life (And How to Protect Yourself from the Bad Ones).

As Tetro explains, antibiotics and antimicrobial products kill germs indiscriminately, destroying the ones that keep us healthy along with those that cause harm. Rather than wipe out entire populations of bacteria, yeasts and fungi, scientists are now searching for ways to bring them into better balance, allowing them to live among us, and within us, harmoniously.

Bad breath

These days, you can find a wide range of products, from muffins to drinking straws, that claim to be “probiotic,” or containing live bacteria that produce health benefits. Many are ineffective. But Tetro believes that one product may have more sticking power than the rest: probiotic chewing gum. Gum is an ideal vehicle for microbes that fight off bad breath and cavities, as the release of saliva while chewing can deliver these microbes to all corners of the mouth and even to the tonsils and sinuses, Tetro explains. The “good”* bacteria, which produce odourless waste products, then colonize and crowd out those that produce foul-smelling chemicals and those responsible for tooth decay. Plus the sticky gum itself traps a significant amount of unwanted bacteria, leaving your mouth fresher when you spit it out.


Some strains of the bacteria species Propionibacterium acnes feed off the gunk produced by our skin, technically known as triglyceride molecules. A pimple erupts when a colony under the skin causes an infection. However, other strains of the same bacteria also feed off triglycerides but don’t create skin-irritating byproducts. Thus, they cause no redness, no unsightly swollen bumps. Tetro says efforts to tease apart the different strains of Propionibacterium acnes may lead to the development of a pimple-preventing skin-care solution that overwhelms acne-causing bacteria with a non-irritating strain.

Tummy troubles

Certain probiotics help prevent or alleviate gas, bloating, diarrhea and constipation by feeding off molecules that irritate the gut, while others produce chemicals that kill off troublesome microbes. They won’t cure your digestive problems, but they can be useful supplements. The “true value” of probiotics, Tetro says, is in boosting the microbial diversity in the gut. While some probiotic producers grow their bacteria in dairy through fermentation, he notes, the probiotics that work most effectively in the human gut may be bacteria that come from “human origin,” that is, from human feces. No need to be squeamish, though, he says. By the time they’re bottled or packaged in pill form, these bacteria have long been cultivated in a lab, and are far removed from their fecal ancestors.

Sour mood

Got the blues? Tetro suggests that psychobiotics could offer relief. Psychobiotics are certain probiotics that produce mood-boosting chemicals with a similar effect as antidepressants. Certain bacteria, he says, can create serotonin, gamma-aminobutyric acid (GABA) and dopamine, which, if absorbed and able to get to the brain, can improve our mood and reduce stress and anxiety. The development of psychobiotics is still in its infancy, so they probably won’t be commercially available for a while yet. But Tetro notes that fermented foods, such as kimchi and cheese, are a natural source of bacteria that produce potentially mood-boosting chemicals.

*While microbes are often described as “good” or “bad,” the reality is not quite so simple. While some microbes co-exist in a mutually beneficial relationship with us, they can cause trouble if they become they become too numerous or find themselves in the wrong place. Similarly, pathogenic, or illness-causing, microbes aren’t always bad for us either.

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