Your brain on yogurt

Probiotic bacteria spread at Colorado universities and businesses

Noah Voreades and Alyssa Whitney in the CSU fermentation lab.
Photo by John Eisle/Colorado State University

Sex, drugs and yogurt: what do they all have in common?

They could all affect the hormone associated with happiness. Serotonin levels can be affected by bacteria like those found in probiotic foods, says John Cryan, a neuroscientist who has co-authored studies on probiotics and stress. The bacteria in probiotic foods, including yogurt, are being studied for the potential benefits to diners’ well-being.

“It’s exactly what antidepressants do,” University of Colorado serotonin scientist Christopher Lowry says of the bacteria he studies. He’s been researching an admittedly “sci-fi” concept: using bacteria as a vaccine against depression and post-traumatic stress disorder (PTSD).

Probiotic bacteria were proven to lower stress hormones and anxiety in mice in a 2011 Proceedings of the Natural Academy of Sciences study. Co-author Cryan says he’s excited about the potential to develop medicines using bacteria to treat anxiety disorders.

Bacteria in human guts — your “microbiota” — are drawing increasing research. Colorado State University recently announced a new major in fermentation science. Tiffany Weir, a fermentation scientist hired to teach the new curriculum, says it will prepare students both for the new field of medical science and for the burgeoning industry. Students can practice fermentation at CSU’s new on-campus brewery. Fermentation happens when microorganisms (bacteria or yeast) digest ingredients, converting them into something else. But beer isn’t “probiotic:” the bacteria aren’t alive when you drink it. Any subsequent feelings of reduced stress aren’t explained by the new bacterial research.

Probiotic fermented foods include yogurt, Kombucha (fermented black tea and sugar), kefir (cultured milk), kimchi, sauerkraut and some frozen yogurt. Most Boulder fro-yo shops use Yoki Bliss yogurt, which contains probiotic bacteria, says Mary Trimble, director of publicity at Twirl.

Even frozen yogurt’s dormant bacteria wake up in your gut, where they join billions of fellow bacteria. Your bacterial cells outnumber your human cells by about 10 to one. You’re a walking bacterial party.

Or, sometimes, a war. A fuzzy line divides friend and foe. Normally, E. Coli bacteria reside peaceably in your gut — but if you ingest one of the few harmful strains, they can kill you. Citing a recent Nature study, Cryan says that diversity is essential to healthy microbiota.

Diversifying your bacteria is hip. Yogurt consumption has doubled in the last decade, according to market analysts at NPD Group. And in local groceries, yogurt keeps demanding more shelf space.

“Last year, we expanded the section by about four feet,” says Tristan Cargnel, dairy manager at Lucky’s Market. Noosa flies off the shelves, he says, and he was even approached about carrying buffalo milk yogurt.

Yogurt can also easily be made at home.

“A lot of customers buy our goat’s milk to make yogurt with it,” says Rob Anderson, owner of Colorado-based Mini Moo and Kids Too.

If you’re not into yogurt, you can still belly up to some bacteria. Local business Esoteric Foods sells its probiotic “zuké pickled things” at the Farmers’ Market and local grocers.

“When you ferment food, you engage it in the battle of bacteria,” Esoteric co-owner Willow King says. “The good guy triumphs… it knocks out E. Coli and other bad bacteria.”

Fermenters affirm their foods’ safety, which has been questioned before.

“The USDA lists no documented cases of food poisoning from fermented foods,” says self-described “fermentation fetishist” Sandor Katz, the author of The Revolution Will Not be Microwaved.

But a 1981 USDA report mentions 114 cases of botulism, which is sometimes caused by bacteria that can contaminate fermented meats. Katz explains that a simple step is now known to prevent the bacteria.

When a mysterious illness struck two women, killing one, in 1995, a Center for Disease Control report mentioned Kombucha as a possible cause. In 2010, Kombucha was pulled from shelves due to concerns about its alcohol content. Two major producers settled lawsuits, but admitted no wrongdoing, according to a beverage industry news site.

“Fermentation makes food safer, not more dangerous,” Katz says. “Meanwhile, we’ve been in what I call ‘the war on bacteria.’”

One bacteria labeled “bad,” he says, is going extinct in humans — just as it’s found to mediate signals that tell us when to stop eating.

Gut microbes have been proven to affect how much mice eat and how many calories they absorb from the same food, says Rob Knight, a CU biologist researching microbiota.

So while Noosa is changing its nutrition labels to reflect a higher fat content than originally believed, it could still be good for your waistline. Its bacteria could help you to absorb fewer calories, and even to know when to stop eating it — a serious challenge, Noosa fans might say.

Feelings of hunger and satiety may be mediated by the “gut-brain axis,” Knight explains. It’s like a phone line in your body, operated by bacteria.

“The bacteria were talking to the brain, we realized,” Lowry says of his serotonin research at CU. “When we looked in mice, just injecting heat-killed bacteria had antidepressant effects.”

When asked why he has to kill the bacteria, he chuckles.

“I guess we don’t have to kill them,” he says. “But we’d have trouble getting regulatory approval for injecting live bacteria into people. But … there are other studies suggesting that eating probiotics might act in a similar way.”

One of Weir’s students, at CSU after military service, hopes to research probiotics’ potential for PTSD sufferers.

Katz expresses concern that research funding is provided only for proprietary strains, not traditional probiotic foods.

But Weir is researching a very traditional tea. Before brewing, the tea leaves ferment, sprouting a yellow fungus. Initial funding came from a Denver clinic practicing Chinese medicine. As Weir finds benefits for diabetes and liver health, she’s submitting grants to the USDA. The National Cancer Institute funds her research on fermented bran.

The National Institute of Mental Health has expressed interest in the role of microbiota, Knight says from a meeting with health officials in Washington, D.C.

Katz predicts that heart and kidney health will soon join the list of bacteria’s beneficiaries. “We’ve just begun to scratch the surface,” he says.