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DRI DIETARY REFERENCE INTAKES FOR Vitamin C, Vitamin E, Selenium, and Carotenoids
Relationship of Vitamin C Intake to Chronic Disease
As suggested earlier, there is reason to expect that the antioxidant vitamins should decrease the risk of cardiovascular disease (Gey, 1995; Jha et al., 1995; Simon, 1992). Several studies have considered the association between vitamin C concentrations in blood and the risk of cardiovascular disease. Singh et al. (1995) found that the risk of coronary artery disease was approximately two times less among the top compared to the bottom quintile of plasma vitamin C concentrations in Indian subjects. A prospective study of 1,605 Finnish men showed that those with increased plasma vitamin C (greater than 11.4 µmol/L [0.2 mg/dL]) had a 60 percent decreased risk of coronary heart disease (Nyyssonen et al., 1997a). The Basel Prospective Study of 2,974 Swiss men reported that plasma vitamin C concentrations greater than 23 µmol/L (0.4 mg/dL) were associated with nonsignificant reductions in the risk of coronary artery disease (Eichholzer et al., 1992) and stroke (Gey et al., 1993). In a 20-year follow-up of 730 elderly adults in Britain, plasma vitamin C concentrations greater than 28 µmol/L (0.5 mg/dL) were associated with a 30 percent decreased risk of death from stroke compared with concentrations less than 12 µmol/L (0.2 mg/dL) (Gale et al., 1995). In a similar study, cross-sectional in design, in 6,624 men and women in the Second National Health and Nutrition Examination Survey, the relative risk of coronary heart disease and stroke was decreased about 26 percent with serum vitamin C concentrations of 63 to 153 µmol/L (1.1 to 2.7 mg/dL) compared with concentrations of 6 to 23 µmol/L (0.1 to 0.4 mg/dL) (Simon et al., 1998).
In addition, several prospective cohort studies have shown that vitamin C intakes between 45 and at least 113 mg/day are associated with reduced risk of cardiovascular disease (Gale et al., 1995; Knekt et al., 1994; Pandey et al., 1995). Gale et al. (1995) reported that in 730 elderly British men and women, vitamin C intakes greater than 45 mg/day were associated with a 50 percent lower risk of stroke than were intakes less than 28 mg/day. There was a nonsignificant 20 percent decrease in the risk of coronary artery disease in this study. Knekt et al. (1994) studied more than 5,000 Finnish men and women and found that women consuming more than 91 mg/day vitamin C had a lower risk of coronary artery disease than those consuming less than 61 mg/day. However, a similar association was not found in the men. In the Western Electric