A new study published in Molecular Psychiatry has shown that eating more fermented foods and fiber daily for just four weeks significantly lowered perceived stress levels. Forty-five participants with relatively low-fiber diets were split into two groups. 

One group met with a dietitian that recommended a psychobiotic diet, which included six to eight daily servings of fruits and vegetables high in prebiotic fibers, such as onions, leeks, cabbage, apples, bananas and oats; five to eight daily servings of grains; three to four servings of legumes per week; and two to three daily servings of fermented foods like sauerkraut, kefir and kombucha. The control group received only general dietary advice based on the healthy eating food pyramid.

The group following the psychobiotic diet reported feeling less stressed compared with those in the control group. Moreover, significant changes in the level of certain key chemicals produced by gut microbes were found in these participants. Some of these chemicals have been linked to improved mental health, which could explain why the participants reported feeling less stressed. The quality of sleep improved in both groups, but those on the psychobiotic diet reported greater sleep improvements.