Vitamin C & Disease Prevention - Part 1

The amount of vitamin C required to prevent chronic disease appears to be more than that required for prevention of scurvy. Much of the information regarding vitamin C and the prevention of chronic disease is based on prospective studies, in which vitamin C intake is assessed in large numbers of people who are followed over time to determine whether they develop specific chronic diseases.

Cardiovascular diseases (heart disease and stroke)

Until recently, the results of most prospective studies indicated that low or deficient intakes of vitamin C were associated with an increased risk of cardiovascular diseases and that modest dietary intakes of about 100 mg/day were sufficient for maximum reduction of cardiovascular disease risk among nonsmoking men and women. In addition, several studies had failed to find significant reductions in the risk of coronary heart disease (CHD) among vitamin C supplement users in well-nourished populations. One notable exception was the First National Health and Nutrition Examination Study (NHANES I) Epidemiologic Follow-up Study. This study found that the risk of death from cardiovascular diseases was 42% lower in men and 25% lower in women who consumed more than 50 mg/day of dietary vitamin C and who regularly took vitamin C supplements, corresponding to a total vitamin C intake of about 300 mg/day. Recent results from the Nurses’ Health Study, based on the follow-up of more than 85,000 women over 16 years, also suggest that higher vitamin C intakes may be cardioprotective. In this study, vitamin C intakes of more than 359 mg/day from diet plus supplements or supplement use itself were associated with a 27-28% reduction in CHD risk. However, in those women who did not take vitamin C supplements, dietary vitamin C intake was not significantly associated with CHD risk. This finding is inconsistent with data from numerous other prospective cohort studies that found inverse associations between dietary vitamin C intake or vitamin C plasma levels and CHD risk. Data from the National Institutes of Health (NIH) indicated that plasma and circulating cells in healthy, young subjects became fully saturated with vitamin C at a dose of 400 mg/day. The results of the NHANES I Epidemiologic Follow-up Study and the Nurses’ Health Study suggest that maximum reduction of cardiovascular disease risk may require vitamin C intakes high enough to saturate plasma and circulating cells, and thus the vitamin C body pool.

With respect to vitamin C and cerebrovascular disease, a prospective study that followed more than 2,000 residents of a rural Japanese community for 20 years found that the risk of stroke in those with the highest serum levels of vitamin C was 29% lower than in those with the lowest serum levels of vitamin C. Additionally, the risk of stroke in those who consumed vegetables 6-7 days of the week was 54% lower than in those who consumed vegetables 0-2 days of the week. In this population, serum levels of vitamin C were highly correlated with fruit and vegetable intakes. Therefore, as in many studies of vitamin C intake and cardiovascular disease risk, it is difficult to separate the effects of vitamin C on stroke risk from the effects of other components of fruits and vegetables, emphasizing the benefits of a diet rich in fruits and vegetables.