MRC/BHF Heart Protection Study

Facts about Antioxidant Vitamins

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Facts about Antioxident Vitamins

  • Atherosclerosis (the narrowing of the walls of the coronary arteries) is caused by a build up of fatty material called atheroma. Atheroma develops when LDL cholesterol undergoes a chemical process known as "oxidation" and is taken up by cells in the coronary artery walls, which then starts to narrow the lumen of the artery,
  • Antioxidant vitamins are a group of dietary substances which protect cells and tissues from oxidative damage. They operate by neutralising the damaging effects of unstable compounds called "free radicals", which are naturally produced in the body and also derived from outside sources (such as cigarette smoking). These vitamins are divided into two groups: fat soluble and water soluble.
  • The MRC/BHF Heart Protection Study (HPS) is investigating a combination of two fat soluble vitamins, vitamin E and beta-carotene, and the most important water soluble vitamin, vitamin C.
  • HPS volunteers are taking two vitamin pills a day (or matching dummy "placebo" pills). These contain a total of 600 mg of vitamin E, 20 mg of beta-carotene (which can be converted to vitamin A according to requirements) and 250 mg of vitamin C. Volunteers were not asked to avoid taking other sources of the vitamins, apart from vitamin E supplements in doses over 100 mg a day.
  • Evidence from observational studies suggests that people with higher intakes of these vitamins from their diets have lower rates of various diseases, including heart disease, cancer, Alzheimer's disease, diabetes and cataracts.
  • Vitamin E is the major antioxidant in LDL particles, and it may affect other processes that occur in atherosclerosis.
  • Vitamin E is found in vegetable fats and oils (e.g. corn, safflower and canola oils, margarine, nuts, seeds and wheat germ), and in green leafy vegetables (e.g. lettuce) to a lesser degree. It is stored in the body in fat tissue and the membranes of all cells.
  • No adverse side-effects have been seen in healthy people at intakes of vitamin E up to 2,000 mg per day.
  • Beta-carotene can also function as a fat soluble antioxidant and is carried with vitamin E in the fatty cores of the LDL particles. Numerous observational studies have suggested that people with higher levels of beta-carotene are at reduced risk of vascular disease and cancer. However no reduction in cardiovascular disease or cancer has been seen recently in two large primary prevention trials.
  • Vitamin C is a major water soluble antioxidant in the blood stream. It can also regenerate vitamin E from its oxidized state back to its active state (so its combination with vitamin E may be more effective than either alone). Vitamin C is required for the production of a number of important substances in the body, including collagen and some hormones. Animal studies have suggested that it is capable of reversing atherosclerosis. Higher vitamin C levels have been linked to lower risk for cataracts, certain cancers, cardiovascular disease, stroke, asthma and obstructive pulmonary disease. There is a strong rationale that vitamin C may reduce risk for cardiovascular disease via several mechanisms, including inhibition of oxidation of LDL and improvement in function of the layer of cells which line the blood vessels and heart (the endothelium).
  • Vitamin C is an essential nutrient and is found in fruits and vegetables. Citrus fruits, tomatoes, and potatoes are major sources. Vitamin C is non-toxic at the doses usually taken.