Vitamin A (in the form of beta-carotene), C, and E are sometimes referred to as the "antioxidant vitamins" and may be sold together as such. Supplements of A, C, and E together with the trace element selenium are also available.
These, together with other food components, act to prevent damage caused by free radicals produced by various essential body functions. Vitamin C is water soluble and found in aqueous solution throughout the body. Vitamin E and beta-carotene are fat-soluble vitamins that exist in lipoproteins and cell membranes; these membranes contain fats (lipids) that are particularly vulnerable to oxidative stress, and the antioxidant vitamins help prevent this.
There is growing evidence that free-radical damage is implicated in the development of many diseases, including atherosclerosis, some cancers, Parkinson's and other neurodegenerative diseases, inflammatory bowel diseases, and lung disease. However, there is little evidence to suggest that supplementation of adequately nourished people with antioxidant vitamins will reduce the incidence of the above diseases. Studies show that people with adequate blood levels of vitamin E, beta-carotene and vitamin C are less likely to develop coronary heart disease and certain cancers.
Epidemiological data from two large studies carried out on health professionals in the USA suggested that women who took more than 200 units and men who took more than 100 units of vitamin E per day had a lower incidence of coronary heart disease. (A unit of vitamin E is equivalent to 1 mg of alpha tocopherol acetate. Vitamin E units are no longer officially used in the UK, but the termn may be used by supplement manufacturers.) There was also a suggestion that supplementation with 50 mg of beta-carotene on alternate days resulted in fewer heart attacks in men who had angina.
Studies using antioxidant supplements in patients with various cancers have not produced unequivocal benefits, but it may be that these vitamins are protective against the early stages of cancer development.
Many of the studies investigating the role of antioxidant vitamins show that people with high intakes of vegetables and fruit have a lower incidence of coronary heart disease and certain cancers, and suggest that the antioxidant vitamins in these foods may be the active agents. It would seem that the best way of obtaining these vitamins is to eat a variety of fruits and vegetables each day - the UK guidelines of five portions per day (equivalent to the 450 g per day advised by the World Health Organization) is a sensible level to aim for.
Antioxidant supplements commonly contain doses of vitamins C and E that are up to 10 times the recommended daily amounts (there are no recommended daily allowances for carotene), and it is probably wise to select one with moderate vitamin content, as there have been studies where potentially harmful effects have been seen.
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