HELSINKI, FINLAND. A new international cohort study sheds further light on the long-standing debate about the role of vitamin-C in coronary heart disease (CHD). The study combined the results of nine prospective studies on intakes of vitamin C, carotenoids and vitamin E.

The authors found that while intake of these vitamins through diet only slightly reduced CHD risk, vitamin C supplementation was associated with significantly lower CHD rates in both men and women. In recent decades, many studies have suggested that vitamin C and other essential nutrients play a role in heart health, possibly by preventing atherosclerosis (hardening of the arteries) that can contribute to CHD. Led by Dr Paul Knekt of the National Public Health Institute in Helsinki, the researchers analyzed data from nearly 300,000 participants and looked at all major CHD events and CHD mortality over a ten-year follow-up period.

Dietary intake of the carotenoid lutein was linked to slightly reduced CHD risk in the first two years of follow-up, as was vitamin-E intake in women, but overall the effect of dietary vitamin E and carotenoids on CHD risk after adjustment for other risk factors was small.

However, taking high doses of vitamin C (more than 700 mg a day) lowered the risk of major CHD events by 25 per cent. As vitamin C supplementation could merely act as an indicator of a generally "healthy" lifestyle, fiber and fat intake were taken into account, but the association remained just as strong. The results are supported by several previous studies suggesting a reduced CHD risk with vitamin C intake over 500 mg per day. On the other hand, no CHD benefit was found from vitamin E supplementation.

An interaction between vitamins C and E was expected, as vitamin C can help regenerate oxidized vitamin E, but the effect was not observed in this study. Despite the significant results concerning vitamin C, the authors conclude that the study does not provide unqualified support for high dose supplementation as they say the effects are not as yet fully understood.
Knekt P, et al. Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts. American Journal of Clinical Nutrition, Vol. 80, December 2004, pp. 1508-1520