“A GOOD way to make yourself unpopular at dinner parties is to point out that a typical person is, from a microbiologist’s perspective, a walking, talking Petri dish. An extraordinary profusion of microscopic critters inhabit every crack and crevice of the typical human, so many that they probably outnumber the cells of the body upon and within which they dwell.
Happily, these microbes are mostly harmless. Some of them, particularly those that live in the gut, are positively beneficial, helping with digestion and keeping the intestines in good working order. That is no surprise—bacteria as much as people have an interest in keeping their homes in sound condition. What is surprising is the small but growing body of evidence which suggests that bacteria dwelling in the gut can affect the brain, too, and thereby influence an individual’s mood and behaviour. The most recent paper on the topic, published this week in the Proceedings of the National Academy of Sciences, reports (like much of the research in this field) on results in mice.
The researchers, led by Javier Bravo of University College, Cork, split their rodent subjects into two groups. One lot were fed a special broth containing Lactobacillus rhamnosus, a gut-dwelling bacterium often found in yogurt and other dairy products. The others were fed an ordinary diet, not fortified with microbes.
The team then subjected the mice to a battery of tests that are used routinely to measure the emotional states of rodents. Most (though not all) of these tests showed significant differences between the two groups of animals….”