Magazine article Psychology Today

Going with the Gut

Magazine article Psychology Today

Going with the Gut

Article excerpt

IT'S BEEN WITH us for the eons that humans have walked the earth. But only in the past decade have scientists recognized that a vast array of bacteria, collectively known as the microbiome, inhabits our gut and serves as an important organ of the body.

Billions of those bacteria, called probiotics, do good: They stimulate the development and function of the immune system, combat the growth of harmful micro-organisms, aid in the process of digestion, even promote healthy body weight. But probably the most unlikely discovery has been that, in ways still under study, the gut plays an important role in mental health. "You can't have a healthy brain without a healthy gut," says psychiatrist Ted Dinan of Ireland's University College Cork.

Maintaining the microbiome in fighting fettle-feeding the beneficial bacteria and keeping them metabolically active-is a massive task that relies on the human diet. Enterprebiotics, nondigestible carbohydrates, otherwise known as fiber. All prebiotics are fiber, but not all fiber is prebiotic-only those complex carbohydrates that resist digestive enzymes but lend themselves to fermentation by bacteria in the large intestine.

In humans, the best-known prebiotics are inulin, fructooligosaccharides (FOS), and galactooligosaccharides (GOS), all variants of sugar substances. And all three, researchers recently discovered, reduce levels of the stress hormone cortisol and influence emotional processing in the brain. They activate a channel of biochemical signaling between the gastrointestinal tract and the nervous system. Prebiotics also increase levels of BDNF, or brain-derived neurotrophic factor, which promotes mental flexibility by stimulating the growth of new neurons.

In a study reported in European Neuropsychopharmacology, Dinan and colleagues fed mice a combination of FOS and GOS for 10 weeks and subjected them to tests that induce behavioral states similar to anxiety and depression in humans. The two prebiotics, he found, functionally "looked like an antidepressant," keeping rats from developing the equivalent of behavioral despair. The prebiotic combo also reduced levels of corticosterone-rodent cortisol-and elevated levels of BDNF in the hippocampus, the brain area crucial for learning and memory.

"We're seeing the first indication that changes in the microbiota by eating these two prebiotics may have a significant impact on stress responses," says Dinan.

It may not be necessary to consume specific prebiotics to promote health and mental health. It may be more important to increase consumption of all fiber-rich foods-something Americans have a particularly hard time doing. …

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