Fermented food consumption and its association with constipation and psychological distress: a cross-sectional study

The microbiota-gut-brain axis highlights a significant diet, gut function, and mental health link. Although fermented foods benefit gut health, how their consumption patterns affect psychological well-being remains unclear. This study investigated associations between fermented food consumption patterns (variety, frequency and specific patterns), constipation, and psychological distress in adults.

This cross-sectional study included 400 adults (aged 18-65) in Turkey. A survey assessed socio-demographics (age, gender, BMI, education, and income) and fermented food frequency questionnaire. Psychological distress was measured using Depression, Anxiety, and Stress Scale-21. Gut function was evaluated using both Constipation Severity Instrument (CSI) and the Bristol Stool Scale for individual stool characterization. Data were analyzed using IBM SPSS 25.0. Associations were examined via correlation and multiple regression analyses (covariates-adjusted). The indirect effect of consumption patterns on distress through CSI was tested using PROCESS Macro (v4.3, Model 4) with 5000 bootstrap samples.

Contrary to expectations, a greater fermented food variety was associated with poorer psychological well-being. Pattern analysis revealed that the 'Low Variety + Medium-High Frequency' pattern was associated with the best psychological state. Conversely, a 'Medium-High Variety + Low Frequency' pattern predicted significantly worse psychological outcomes. This negative effect was fully mediated by increased constipation severity (p < 0.05).

The fermented food-psychological health relationship is pattern-dependent. Consistent consumption of a limited variety was more strongly associated with positive gut-brain axis-related outcomes than sporadic consumption of a wide variety. These results emphasize incorporating specific, sustained fermented food patterns into dietary recommendations and warrant longitudinal and interventional studies.