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Introduction
Many epidemiological studies have led to the observation that diets rich in vegetables and fruit are associated with higher life expectancy and it may be the antioxidants contained therein which are of principal importance for the beneficial effects. The cumulative evidence shows that lower risks of certain cancers and coronary heart disease are associated with diets rich in antioxidant-containing components.
The World Health Organization (WHO) have advised the intake of at least 500g/day of mixed fresh fruit and vegetables -- a recommendation that has been endorsed by Government agencies and translated into at least five servings (helpings) per day. (This is not only because of the high level of antioxidants but also because fruit and vegetables are low in fats, high in fibre and good sources of vitamins and minerals.)
There is considerable evidence for a role for the antioxidant nutrients vitamins E, C and beta-carotene in the maintenance of health, in contributing to the decreased incidence of disease (cancer, cataract, cardiovascular disease) and in protecting against the recurrence of pathological events. Extended dietary surveys in the USA reveal that the calculated intake of essential antioxidants such as vitamin C, beta-carotene, vitamin E is inversely related to the risk of ischaemic heart disease, as it is for certain forms of cancer. Plasma concentrations of diet-derived antioxidants show inverse correlations with cancer incidence and cardiovascular disease, although with a different rank order of antioxidants
1
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* Decreased cancer risk: P-carotene>vitamin C>vitamin E.
* Decreased coronary heart disease risk: vitamin E>beta-carotene>vitamin C.
Fruit and vegetables are the principal sources of two of the major dietary antioxidants: vitamin C and the carotenoids (Table I). (all tables and figures omitted) Vitamin C occurs in citrus fruits, green peppers, cabbage, strawberries, green leafy vegetables, and beta-carotene in carrots, dark leafy greens, orange and yellow vegetables and orange fruits. Although many people do not realize it, certain fruit and vegetables contain the third major antioxidant nutrient vitamin E, although major sources are cereal oils, olive oil, nuts.
Compelling chemical, biochemical, clinical and epidemiological evidence supports the contention that the antioxidant nutrients exert vital contributions towards the prevention or delayed onset of cancer and cardiovascular disease. Antioxidants are considered to exert their effects by attenuating oxidative events that contribute to...
