B-Carotene
There is some indication that increased dietary intake of B-carotene is associated with reduced risk of CHD although again the evidence is less convincing than that for vitamin E. In the prospective Nurses Health Survey, consumption of vitamin A and B-carotene in food and supplements weakly predicted the incidence of CHD; Gaziano and Hennekens reported a 22% risk reduction for women in the highest quintile of B-carotene compared with those in the lowest. No adjustment was made for the potentially confounding effect of other antioxidant vitamins in multivitamin preparations. However, a small prospective study on 1271 elderly people also demonstrated an inverse relationship between B-carotene intake in fruit, and vegetables and subsequent cardiovascular death. Similar findings have been shown for serum carotenoid level and CHD risk, and carotenoid intake and carotid artery plaque thickness.
Several studies indicate that dietary and circulating levels of B-carotene affect smokers more than nonsmokers. In the Health Professionals Follow-Up Study, high B-carotene intake was associated with reduced CHD risk in current smokers and exsmokers (70% risk reduction' but not never-smokers, after adjustment for cardiovascular risk factors and vitamin C and E intake. It was suggested that a high dietary intake of ~-carotene is especially important in smokers who have both an increased demand for antioxidants (to combat smoking-induced free radicals) and a correspondingly lower circulating level for a given dietary intake. However, (B-carotene supplements in smokers may have harmful effects as discussed in the next section.
