Ever hear someone say “you think with your stomach”? As it turns out, it just so happens to be more fact than fiction. Several new studies have confirmed what many have suspected to be true for years: Probiotics have an effect on mental wellbeing.
Studies in Mice
Researchers experimenting on mice found that Lactobacillus—the bacteria commonly found in yogurt—may help reduce depression symptoms due to chronic stress. The study subjected mice to high stress levels until they developed despair-like behaviors. They found that these stressed mice exhibited lower levels of Lactobacillus. These mice also experienced heightened metabolic kynurenine levels, which is thought to influence mood symptoms. When the researchers treated the mice by increasing their levels of Lactobacillus reuteri, they found that the metabolic changes and the behavioral despair resolved. That is, once the probiotic levels returned to normal, so did the kynurenine levels and the behavior of the mice. The researchers suggest that this finding indicates that increasing Lactobacilluslevels may help reduce the physiological changes associated with stress, leading to less severe depressive symptoms.
With more than 16 million adults in the United States alone reporting a major episode of depression within the last year, probiotics may be the next big thing in the supplement industry.
Studies In Humans
Another Study published in Nutrition entitled “Clinical and metabolic response to probiotic administration in patients with major depressive disorder: A randomized, double-blind, placebo-controlled trial.”
The study used three strains of probiotics in a capsule (Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum, two billion colony forming units of each), and checked not only records of personal diet but also serum glucose and other measures of metabolism along with a lab test that looked at inflammation levels. After eight weeks of the study, depression scores were significantly reduced in the group taking probiotics compared to placebo along with lower plasma insulin measures and inflammation levels. Apart from the probiotics the diet and weight were no different between the groups. This meant the probiotics seemed to decrease inflammation along with symptoms of depression, and perhaps began to influence the metabolism positively.
Mechanism Of Action
It is theorized that the gut bacteria work as a defense layer preventing the flow of toxins that could potentially get into the blood and cause inflammation. Probiotics also seem to help in the communication of neurons between the gut and the brain. More research is continuing to explore the important role of kynurenine, one of the stress related toxins seemingly reduced by probiotics.
