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Observational epidemiological surveys (WG 3) page 54
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2-3 Antioxidant Vitamins
The antioxidant vitamins have long been considered as being some of the most important functional
components of fruit and vegetables. However, the epidemiological evidence to support this
hypothesis is somewhat controversial, especially for vitamin C. (Tangney et al., 1997; Faggiotto et
al., 1998; Ness and Powles, 1997; Law and Morris, 1998).
2-3-1 Vitamin C
Overall, the data are inconclusive for a protective effect of vitamin C against atherosclerotic disease
(Ness and Powles, 1996; Jacob, 1998) although limited data is consistent with vitamin C being
protective against stroke (Ness et al., 1996). Prospective studies where dietary intakes or plasma
levels of vitamin C have been used as proxy nutrients for indicators of fruit and vegetables intake
are summarized in tables 31-32. Studies using serum levels are more reliable than those using
dietary intake. There are strong indicators that low serum vitamin C levels are a high risk factor for
development of coronary disease (Vita et al., 1998; Nyyssonen et al., 1997; Gale et al., 1995;
Eichholzer et al., 1992). The dietary studies, although rather inconclusive, are in agreement with the
serum studies in the NHANES II follow-up study (Simon et al., 1998), the increase in CHD
prevalence was mainly found among individuals with low to normal vitamin C blood levels. The
Finnish study by Nyyssonen et al., (1997) showed significant increased risk in vitamin C deficient
Finnish men but no difference in normal to high vitamin C levels. These findings may explain why
there were insignificant effects of vitamin C intake in well-nourished populations such as the Iowa
postmenopausal women, Nurses Health and the Health Professionals studies (Kushi et al., 1996-b;
Stampfer et al., 1993; Rimm et al., 1993). The NHANES I Epidemiologic follow-up study found
that individuals with the highest intakes of vitamin C had a 25-50% reduction in cardiovascular
mortality (Enstrom et al., 1992). Dietary vitamin C was also associated with a decreased risk of
CHD death among Finnish women (Knekt et al., 1994) but not in the Rotterdam study (Klipstein-
Grobush et al., 1999). There is no published clinical trial examining the independent effect of
vitamin C on CHD.