Association of dietary protein intake and coffee consumption with serum homocysteine concentrations in an older population

Background: Elevated blood concentrations of total homocysteine (tHcy) have been implicated in the pathogenesis of atherosclerotic cardiovascular disease. Previous studies identified suboptimal nutritional status and dietary intake of folate, vitamin B-6, and vitamin B-12 as determinants of elevated tHcy. Objective: We identified other nutritional factors associated with tHcy in 260 retired schoolteachers in the Baltimore metropolitan area. Design: We performed observational analyses of baseline and 2-4-mo follow-up data collected in a study designed to test the feasibility of conducting a large-scale clinical trial of vitamin supplements by mail. The study population consisted of 151 women and 109 men with a median age of 64 y. At baseline, each participant completed a food-frequency questionnaire. At follow-up, fasting serum tHcy was measured. Results: In multivariable linear regression and generalized linear models, there was an independent, inverse dose-response relation between dietary protein and ln tHcy (P = 0.002) and a positive, significant dose-response relation between coffee consumption and ln tHcy (P for trend = 0.01). Other significant predictors of ln tHcy were creatinine (positive; P = 0.0001) and prestudy use of supplemental B vitamins (inverse; P = 0.03). In stratified analyses restricted to persons receiving standard multivitamin therapy, the association of ln tHcy with dietary protein and coffee persisted. Conclusions: These results support the hypothesis that increased protein intake and decreased coffee consumption may reduce tHcy and potentially prevent atherosclerotic cardiovascular disease and other disease outcomes.