Folate intake and incidence of hypertension among American young adults: a 20-y follow-up study

Background: Laboratory studies suggest that folate intake may decrease blood pressure (BP) through increasing nitric oxide synthesis in endothelial cells and/or reducing plasma homocysteine concentrations. However, human studies, particularly longitudinal data, are limited. Objective: Our objective was to investigate whether dietary folate intake is associated with the 20-y incidence of hypertension. Design: We prospectively followed 4400 men and women (African Americans and whites aged 18-30 y) without hypertension at base-line (1985) in the Coronary Artery Risk Development in Young Adults study 6 times, in 1987, 1990, 1992, 1995, 2000, and 2005. Diet was assessed by dietary-history questionnaire at baseline and in 1992 and 2005. Incident hypertension was defined as the first occurrence at any follow-up examination of systolic BP >= 140 mm Hg, diastolic BP >= 90 mm Hg, or use of antihypertensive medication. Results: A total of 989 incident cases were identified during the 20-y follow-up. After adjustment for potential confounders, participants in the highest quintile of total folate intake had a significantly lower incidence of hypertension (HR: 0.48; 95% CI: 0.38, 0.62; P-trend < 0.01) than did those in the lowest quintile. The multivariable HRs for the same comparison were 0.33 (95% Cl: 0.22, 0.51; P-trend < 0.01) in whites and 0.54 (95% CI: 0.40, 0.75; P-trend < 0.01) in African Americans (P-interaction = 0.047). The inverse associations were confirmed in a subset of the cohort (n = 1445) with serum folate measured at baseline and in 1992 and 2000. Conclusions: Higher folate intake in young adulthood was longitudinally associated with a lower incidence of hypertension later in life. This inverse association was more pronounced in whites. Additional studies are warranted to establish the causal inference. Am J Clin Nutr 2012;95:1023-30.