Meta-analysis of 633,317 individuals shows associations between healthy diets and depression, anxiety and stress in 23 low- and middle-income countries

Poor diet quality related to common mental disorders contribute to global health syndemics. However, there is no synthesis quantifying associations specifically in Low- and Middle-Income Countries (LMIC) where these concomitant health burdens are most prevalent. We used a previously generated systematic Evidence and Gap Map of over 3000 peer-reviewed studies linking food security and nutrition to anxiety, depression, stress and mental wellbeing (2000-2024). From this, we selected studies investigating associations between healthy diets and depression, anxiety and stress measured by validated tools. Eighty-three eligible studies from 23 countries (depression n=69; anxiety n=43; stress n=26), and 65 LMIC sample populations, reported statistical measures for 633,317 unique individuals. Healthy diets were associated with less depression, anxiety, and stress. The Standardized Mean Differences (SMD) were -0.29 for depression (95% CI -0.35 to -0.23), -0.25 for anxiety (95% CI -0.35 to -0.16), and -0.24 for stress (95% CI -0.33 to -0.14). Results remained robust when restricted to low Risk of Bias studies. Findings were similar in direction and magnitude across study designs, dietary measurements, diagnostic tools, country income levels, and estimates adjusted for socio-economic status. Methodological limitations (e.g., cross-sectional design) and few studies from low-income countries created evidence gaps. Building on the interrelationship between diet and mental health can inform actions to improve both in settings with disproportionate health vulnerabilities.