Eating sauerkraut, pickles and yoghurt may be the answer for young adults suffering from social anxiety.
Students who ate more fermented food had fewer social anxiety symptoms, say researchers from the University of Maryland and the William and Mary college in Virginia.
"It is likely that the probiotics in the fermented foods are favourably changing the environment in the gut, and changes in the gut in turn influence social anxiety," says Professor Matthew Hilimire.
"I think that it is absolutely fascinating that the micro-organisms in your gut can influence your mind."
About 700 students were asked about fermented foods consumed over the previous 30 days, their exercise and consumption of fruit and vegetables.
"This study shows that young adults who are prone towards anxiety report less social anxiety if they frequently consume fermented foods with probiotics," said co-researcher Professor Jordan DeVylder.
"These initial results highlight the possibility that social anxiety may be alleviated through low-risk nutritional interventions, although further research is needed to determine whether increasing probiotic consumption directly causes a reduction in social anxiety."
The study, to be published in the journal Psychiatry Research, found the effect was greatest among those at genetic risk for social anxiety disorder as measured by neuroticism.
The second finding was that more exercise was related to reduced social anxiety.
Some of the foods the students were asked about included yoghurt, kefir, fermented soy milk, miso soup, sauerkraut, some dark chocolates, microalgae juices, pickles, tempeh and kimchi.