The study points to a promising link. It doesn't prove cause and effect, though, says Matthew Hilimire, PhD, an assistant professor in the department of psychology at the College of William and Mary.
Social anxiety is a disorder that fills you with a fear of being judged by others or embarrassed in front of them in ordinary situations.
Future research could look into whether eating fermented foods helps people get more out of traditional treatments, like medication or cognitive-behavioral therapy, Hilimire says.
The study, which is published in Psychiatry Research, included 710 students taking intro psychology courses at the College of William and Mary. They filled out questionnaires about their fermented food eating habits, rated how worried (or neurotic) they tended to be, and said whether or not they had social anxiety.
The questionnaire asked about a variety of foods, including:
- Kefir or food or drinks that contain yogurt
- Soy milk
- Miso soup
- Dark chocolate
- Juices that contain microalgae
While not all of those foods necessarily have the live, active cultures that some yogurts contain, they still have the potential to contain the good bacteria, Hilimire says.
Researchers also considered factors including eating healthy foods and amount of exercise in their findings.
In students with high degrees of neurotic feelings, eating more fermented food was linked to fewer symptoms of social anxiety.
"Probiotics have also been shown to modify the body's response to stress, and stress response is highly linked to mental health disorders, such as social anxiety," he says.
Research on gut bacteria is expanding a lot, as is research on genetic influences on mental disorders, says Bonnie J. Kaplan, PhD, who studies nutrition and mood at the University of Calgary.
"This study is interesting in how it ties together several relevant threads of personality, food intake, and exercise,” she says.
"Also of interest is the fact that the information was not collected from a clinical sample of people with diagnosed anxiety disorders... participants were first-year psychology students in an American liberal arts university. This means the results have implications for broad, population health," she says.
But more research is needed, she notes.