Plasma concentrations of ascorbic acid and C-reactive protein, and risk of future coronary artery disease, in apparently healthy men and women: the EPIC-Norfolk prospective population study
High plasma concentrations of ascorbic acid, a marker of fruit and vegetable intake, are associated with low risk of coronary artery disease. Whether this relationship is explained by a reduction in systemic inflammation is unclear. We investigated the relationship between ascorbic acid plasma concentration and coronary artery disease risk, and in addition whether this relationship depended on classical risk factors and C-reactive protein (CRP) concentration. We used a prospective nested case–control design. The study consisted of 979 cases and 1794 controls (1767 men and 1006 women). Increasing ascorbic acid quartiles were associated with lower age, BMI, systolic and diastolic blood pressure, and CRP concentration, but with higher HDL-cholesterol concentration. No associations existed between ascorbic acid concentration and total cholesterol concentration or LDL-cholesterol concentration.
When data from men and women were pooled, the risk estimates decreased with increasing ascorbic acid quartiles such that people in the highest ascorbic acid quartile had an odds ratio for future coronary artery disease of 0·67 (95% CI 0·52, 0·87) compared with those in the lowest quartile (P for linearity=0·001). This relationship was independent of sex, age, diabetes, smoking, BMI, LDL-cholesterol, HDL-cholesterol, systolic blood pressure and CRP level. These data suggest that the risk reduction associated with higher ascorbic acid plasma concentrations, a marker of fruit and vegetable intake, is independent of classical risk factors and also independent of CRP concentration.