Cross-sectional and longitudinal associations between dietary intake and depressive symptoms in young South African adults: The African-PREDICT study

IntroductionDepression is highly prevalent among young adults worldwide. While research links health behaviours, such as dietary intake, to depression, few studies have examined these associations among young adults in low- and middle-income countries, including South Africa. This study investigated whether dietary intake was associated with an increased risk of depression in a cohort of young South African adults, aged 20-30 years, as part of the Global burden of disease Lifestyle And mental Disorder (GLAD) project. MethodsThis five-year prospective cohort study was conducted in the North West Province of South Africa in accordance with the GLAD project protocol (DERR1-10.2196/65576). Dietary exposures were evaluated using three non-consecutive 24-hour dietary recalls, measuring daily intake of various food groups and nutrients as defined by the Global Burden of Disease study. Depression outcomes were assessed at baseline (N=1039) and follow-up (N=551) using the Patient Health Questionnaire (PHQ-9, cut-off [≥]10). Logistic and Poisson regression analyses were performed, with results presented as odds ratios (OR) and relative risk ratios (RR), respectively. Four models were run: unadjusted, sociodemographic-adjusted, total energy (TE) intake-adjusted and fully adjusted (including sociodemographic information and TE intake). For longitudinal analyses of incident depression, baseline depression cases were additionally excluded (n=403). ResultsParticipants (average age 24.55 years) had a balanced distribution of sex (51.4% female) and race (48.6% Black), and a 29.45% baseline prevalence of depression. Higher milk intake was associated with a lower risk of incident depression (RR=0.94, 95% CI 0.91-0.98) in the TE-adjusted longitudinal model. Cross-sectionally, higher sugar-sweetened beverage consumption associated with higher odds of depression, while higher calcium intake (OR=0.48, 95% CI 0.31; 0.76) and vegetable consumption (OR=0.74, 95% CI 0.61, 0.91) were associated with lower odds of depression after TE intake adjustment. Higher fibre intake was associated with lower odds of depression in the unadjusted model. ConclusionHigher daily milk intake was associated with a lower risk of depression, while higher calcium, vegetable, and fibre intake were associated with a lower prevalence of depression in young adults. These findings suggest that prevention strategies for common mental disorders could include dietary approaches within mental health care.