Associations of dietary magnesium and omega-3 fatty acid intake with mental health indicators among Korean adults: a population-based cross-sectional study

Abstract Background Dietary magnesium and omega-3 fatty acid intake have been studied in relation to mental health, with findings varying across populations and exposure measures. We examined separate and joint associations of food-derived intake with elevated depressive symptoms, elevated anxiety symptoms, and suicidal ideation among Korean adults. Methods This cross-sectional study included 4,411 adults aged ≥ 19 years from the 2022 Korea National Health and Nutrition Examination Survey. Nutrient intake was assessed by a single 24-hour recall; separately surveyed supplement quantities were not added. High magnesium intake was defined as ≥ 350 mg/day in men and ≥ 250 mg/day in women, and high omega-3 intake as ≥ 1.5 g/day. Elevated depressive and anxiety symptoms were defined as Patient Health Questionnaire-9 and Generalized Anxiety Disorder-7 scores ≥ 10, respectively. Suicidal ideation referred to the previous 12 months. Survey-weighted logistic regression incorporated strata, clusters, integrated health–nutrition weights, and 13 covariates. Multiplicative nutrient interaction and exploratory symptom-score trends across intake quartiles were evaluated. Results The adjusted association between high omega-3 intake and elevated depressive symptoms was not statistically significant (odds ratio [OR] 0.833, 95% confidence interval [CI] 0.556–1.249; p = 0.375). Adjusted associations with elevated anxiety symptoms (OR 0.929, 95% CI 0.631–1.367; p = 0.705) and suicidal ideation (OR 0.822, 95% CI 0.557–1.215; p = 0.324) were also not statistically significant. All 12 primary adjusted tests, including magnesium, joint intake, and nutrient interaction, had p > 0.05. The exploratory omega-3–PHQ-9 trend had nominal p = 0.026 and an approximate Benjamini–Hochberg-adjusted p = 0.104 across four trend tests. Conclusions Adjusted associations between the examined intake categories and mental health indicators were not statistically significant. Imprecise estimates and a single-day dietary assessment leave the relationships with usual intake uncertain. Prospective studies with repeated dietary measurements could help clarify the direction and magnitude of these associations.