What you eat can have a major impact on how you feel emotionally.
A diet rich in probiotics -- which support the growth of "healthy" bacteria in the gut -- is known to boost digestive health and can even improve a person's immune system. But now an increasingly robust body of evidence suggests that gut bacteria may exert a significant effect on brain function and mental health.
Probiotics are live bacteria and yeast that can be found in your body, as well as in supplements and foods fermented with live active cultures such as some yogurts, kombucha, sauerkraut, kimchi, and kefir. These "good" bacteria are known to promote digestive and immune health, and researchers are discovering that they may support mental health as well.
Once considered a fringe idea, a growing number of scientists have become interested in probiotics and prebiotics as potential treatments for anxiety, depression and other mental health problems. And in a small, new study at Leiden University, researchers found additional support for the idea: they report that among 40 healthy subjects, those who underwent four weeks of probiotic treatment showed a decrease in negative thoughts and feelings.
For the study, the researchers administered multistrain probiotics -- meaning that they contained different types of bacteria -- to 20 healthy participants every day for four weeks. The other 20 participants received a placebo. At the outset of the study and then again after the month had gone by, the participants filled out a questionnaire assessing sensitivity to depression.
Participants who took the probiotics were significantly less reactive to sad moods. Improving the balance of healthy bacteria in the gut seemed to have a protective effect against rumination, the type of obsessive negative thinking that often predicts depression.
Check out this video for an explanation from the researchers:
The researchers don't yet know how probiotics reduce sad mood, but it's possible that they increase levels of plasma tryptophan, a key neurochemical involved in mood, which can be found in the gut.
"Unquestionably, further research needs to be carried out," the study's lead author, Dr. Lorenza Colzato of Leiden University, told The Huffington Post in an email. "But the hope is that probiotics supplementation may work as a potential and effective preventive strategy for depression."
Boosting healthy bacteria in the gut may also be an effective way to treat anxiety. In a recent study, neuroscientists at Cambridge University found a short course of prebiotics -- non-digestible dietary fiber that act as food for good bacteria -- to have an anti-anxiety effect, lessening study subjects' emotional responses to negative stimuli.
"It is likely that these compounds will help to manage mental illness," the study's lead author, Oxford neurobiologist Dr. Philip Burnet, told The Huffington Post in January. "They may also be used when there are metabolic and/or nutritional complications in mental illness, which may be caused by long-term use of current drugs."
Leiden University's findings were published in the journal Brain, Behavior and Immunity.