To further investigate the mind-altering potential of benign bacteria, Cryan and colleagues at McMaster University in Canada fed mice a broth containing a benign bacterium, Lactobacillus rhamnosus.
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In this case, the side effects appeared to be beneficial... the rodents spent more time exploring narrow elevated walkways and wide-open spaces, which are scary to rodents, and they exhibited a smaller spike in stress hormone levels when the researchers put them in water. "This was really exciting because it tells us the animals are more chilled out and don't mount the same stress response," Cryan says.
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"This is pioneering work," says Mark Lyte, a microbial endocrinologist at the Texas Tech University Health Sciences Center in Abilene. "It's really showing that you can alter emotional states by regulating the microbiome."