The importance of a healthy gut microbiome is reinforced by new research that suggests depression and anxiety may be linked to gut bacteria in obese people. Noticing that obese people with type 2 diabetes were more likely to suffer from acute depression, researchers at the Joslin Diabetes Center at Harvard Medical School set out to understand what factors might be the cause.
They narrowed in on the gut after observing the behavior of mice given a high-fat diet. The mice displayed significantly more signs of depression, anxiety and obsessive behavior than mice on standard diets. However, researchers were able to see a reversal in behavior when antibiotics were introduced into their drinking water which altered their gut microbiome.
“As endocrinologists, we often hear people say that they feel differently when they’ve eaten different foods,” said Dr. Ronald Kahn. “What this study says is that many things in your diet might affect the way your brain functions, but one of those things is the way diet changes the gut bacteria or microbes. Your diet isn't always necessarily just making your blood sugar higher or lower; it's also changing a lot of signals coming from gut microbes and these signals make it all the way to the brain.”
Kahn and his team at Harvard have long studied mice prone to developing obesity, diabetes and related metabolic diseases when given high-fat diets. They were able to duplicate the anxiousness in healthy mice when they had bacteria from depressed mice introduced into their gut. But that behavior was not observed when the healthy mice were given bacteria from the gut of mice that had already been exposed to the antibiotics. “This proves that these behaviors are driven to some significant extent by the gut microbiome,” Kahn said.
Kahn and his colleagues are now working to identify the specific type of bacteria involved in these processes with the goal of finding ways to improve the gut microbiome and ultimately the mental outlook of those suffering from anxiety and depression.
“Antibiotics are blunt tools that change many bacteria in very dramatic ways,” Kahn says. “Going forward, we want to get a more sophisticated understanding about which bacteria contribute to insulin resistance in the brain and in other tissues. If we could modify those bacteria, either by putting in more beneficial bacteria or reducing the number of harmful bacteria, that might be a way to see improved behavior.”