Steinberg et al.61 proposed that LDL cholesterol is only atherogenic when it is oxidized, and that antioxidants might therefore protect against CHD. There is a considerable amount of epidemiological evidence that supports the hypothesis that dietary antioxidants such as carotenoids, vitamin C, vitamin E, selenium, and various non-nutrients may reduce CHD risk, but this effect has not been firmly established by clinical trials.46
Vegetarian diets are generally higher in carotene, vitamin C, and vitamin E than non-vegetarian diets. For example, in a study in New Zealand, Zino et al.62 reported that vegetarian Seventh-Day Adventists consumed more fruits and vegetables than both non-vegetarian Seventh-Day Adven-tists and non-Adventist non-vegetarians who were subjected to an intervention designed to increase their intake of fruits and vegetables. Plasma concentrations of P-carotene and a-tocopherol were also higher in the vegetarians than in the other groups. Similar results have been reported in other studies.63
Although vegetarian diets are generally relatively rich in carotene, vitamin C, and vitamin E, they are not necessarily rich in selenium, another antioxidant nutrient. Selenium levels are high in fish and moderately high in meat, but the selenium content of plant foods is strongly determined by the selenium content of the soil. Some small studies have reported low selenium levels in vegetarians and vegans, for example, in Britain,64 Finland,65 and Slovakia,66 probably reflecting the low soil selenium levels in these countries.
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