Yoghurt, kimchi and other fermented foods are often promoted as a way to support mood through the gut. Trials of probiotics have given mixed signals, and little is known about what ordinary eating habits do. A new study of Malaysian students suggests that how much fermented food they ate made no clear difference to their depression, anxiety or stress.

Researchers at Universiti Malaysia Sabah and partner institutions ran a cross-sectional online survey of 212 undergraduates between June and December 2025. The findings appear in The Open Psychology Journal. The team compared fermented food intake with symptoms of depression, anxiety and stress, after adjusting for other factors.

Students were recruited through university channels and social media, and all were aged 18–30. The average age was 21.2, and 77.4 per cent were women. Anyone being treated for a psychiatric disorder, or following a diet that restricted fermented foods, was excluded.

Fermented foods were counted with a questionnaire covering the previous month. It listed traditional Sabah products such as tempoyak, tapai and belacan, along with commercial ones such as yoghurt, kefir, kimchi and tempeh. Symptoms were measured with the Malay version of the Depression Anxiety Stress Scales, a standard screening tool.

The typical student ate 2 servings of fermented food a week. Moderate to extremely severe symptoms were reported by 29 students for depression, 75 for anxiety and 22 for stress. Each extra weekly serving was not significantly linked to any of them, even after adjusting for age, gender, ethnicity, year of study, living arrangements, chronic illness and probiotic supplement use.

Splitting students into four groups by intake did not reveal a clear pattern either. Depression was less common in the second group and more common in the highest, but the estimates were very imprecise. Exploratory checks on whether probiotic supplements or health motivations changed the result also found nothing significant.

The authors suggest that real-world eating differs from controlled trials, which use set strains and daily doses. Intake in this sample was fairly low, and most students were not clinically unwell. That makes small effects harder to spot.

The study has clear limits. It was a snapshot, so it cannot show cause and effect, and symptoms were self-reported on a screening scale rather than diagnosed. The food questionnaire was designed for the study and had not been fully validated. Women made up most of the sample, only 29 and 22 students had moderate or worse depression and stress, and sleep, exercise and diet quality were not measured.

Controlled trials of probiotics and fermented foods have sometimes reported better mood, while observational work has been less consistent. This study adds a Southeast Asian example, with local foods, that finds no link. For now, the clearest message is that ordinary fermented food intake did not track with students’ mental health.