Dietary Protein Sources and All-Cause and Cause-Specific Mortality: The Golestan Cohort Study in Iran

Introduction Dietary protein comes from foods with greatly different compositions that may not relate equally with mortality risk. Few cohort studies from non-Western countries have examined the association between various dietary protein sources and cause-specific mortality. Therefore, the associations between dietary protein sources and all-cause, cardiovascular disease, and cancer mortality were evaluated in the Golestan Cohort Study in Iran. Methods Among 42,403 men and women who completed a dietary questionnaire at baseline, 3,291 deaths were documented during 11 years of follow up (2004–2015). Cox proportional hazards models estimated age-adjusted and multivariate-adjusted hazard ratios (HRs) and 95% CIs for all-cause and disease-specific mortality in relation to dietary protein sources. Data were analyzed from 2015 to 2016. Results Comparing the highest versus the lowest quartile, egg consumption was associated with lower all-cause mortality risk (HR=0.88, 95% CI=0.79, 0.97, p_trend=0.03). In multivariate analysis, the highest versus the lowest quartile of fish consumption was associated with reduced risk of total cancer (HR=0.79, 95% CI=0.64, 0.98, p_trend=0.03) and gastrointestinal cancer (HR=0.75, 95% CI=0.56, 1.00, p_trend=0.02) mortality. The highest versus the lowest quintile of legume consumption was associated with reduced total cancer (HR=0.72, 95% CI=0.58, 0.89, p_trend=0.004), gastrointestinal cancer (HR=0.76, 95% CI=0.58, 1.01, p_trend=0.05), and other cancer (HR=0.66, 95% CI=0.47, 0.93, p_trend=0.04) mortality. Significant associations between total red meat and poultry intake and all-cause, cardiovascular disease, or cancer mortality rate were not observed among all participants. Conclusions These findings support an association of higher fish and legume consumption with lower cancer mortality, and higher egg consumption with lower all-cause mortality.