Association between omega-6 and omega-3 fatty acids intake, body mass index and depression in young Iranian adults: a cross sectional study

BACKGROUND: Omega-3 polyunsaturated fatty acids (PUFAs) play important roles in cardiometabolic and mental health, and the dietary omega-6/omega-3 ratio has emerged as a key determinant of inflammatory and psychological outcomes. Despite generally low omega-3 intake in Iran, little is known about how dietary fatty acid patterns relate to mental health in young adults, who may be particularly vulnerable due to nutritional constraints and high rates of depressive symptoms. Moreover, prior studies in Iran have not simultaneously examined omega-3 intake, the omega-6/omega-3 ratio, BMI, and depressive symptoms within the same analytical framework. OBJECTIVE: This cross-sectional study aims to investigate the associations between the intake of omega-6 and omega-3 fatty acids, the omega-6:3 ratio, body mass index, and depressive symptoms in young Iranian adults. METHODS: Dietary data on omega-3 and omega-6 fatty acids were obtained through semi-quantitative food-frequency questionnaire (FFQ). The Beck Depression Inventory-II (BDI-II) was used to measure depressive symptom. We applied logistic regression to assess the relationships between variables. RESULTS: A total of 440 university students aged 18-30 years were included. After adjustment for age, sex, and total energy intake, higher BMI was associated with greater odds of depressive symptoms (OR: 1.11; 95% CI: 1.04-1.20). Compared with the lowest quintile, participants in the highest quintile of omega-3 intake had lower odds of depressive symptoms (OR: 0.34; 95% CI: 0.17-0.71). In contrast, a higher omega-6/omega-3 ratio was associated with greater odds of depressive symptoms, with nearly tenfold higher odds observed in the highest versus lowest quintile (OR: 9.94; 95% CI: 3.89-25.43). CONCLUSION: Higher omega-3 intake was associated with lower odds of depressive symptoms, whereas higher BMI and a greater omega-6/omega-3 ratio were associated with higher odds. These findings suggest that dietary fatty-acid balance and body weight may be relevant correlates of mental health in young adults. Prospective and interventional studies are needed to clarify causal relationships.