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Facts about Antioxidant VitaminsThis material is also available as an MS-Word document. Facts about Antioxident Vitamins
Atherosclerosis (the narrowing of the walls of the coronary arteries) is caused by abuild up of fatty material called atheroma. Atheroma develops when LDL cholesterolundergoes a chemical process known as "oxidation" and is taken up by cells in thecoronary artery walls, which then starts to narrow the lumen of the artery, Antioxidant vitamins are a group of dietary substances which protect cellsand tissues from oxidative damage. They operate by neutralising the damaging effectsof unstable compounds called "free radicals", which are naturally produced in thebody and also derived from outside sources (such as cigarette smoking).These vitamins are divided into two groups: fat soluble and water soluble. 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 ofbeta-carotene (which can be converted to vitamin A according to requirements) and250 mg of vitamin C. Volunteers were not asked to avoid taking other sources of thevitamins,apart from vitamin E supplements in doses over 100 mg a day. Evidence from observational studies suggests that people with higher intakesof 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 affectother processes that occur in atherosclerosis. Vitamin E is found in vegetable fats and oils (e.g. corn, safflower andcanola 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 andthe membranes of all cells. No adverse side-effects have been seen in healthy people at intakes ofvitamin E up to 2,000 mg per day. Beta-carotene can also function as a fat soluble antioxidant and is carriedwith vitamin E in the fatty cores of the LDL particles. Numerous observational studieshave suggested that people with higher levels of beta-carotene are at reduced risk ofvascular disease and cancer. However no reduction in cardiovasculardisease 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 canalso regenerate vitamin E from its oxidized state back to its activestate (so its combination with vitamin E may be more effective thaneither alone). Vitamin C is required for the production of anumber of important substances in the body, including collagen andsome hormones. Animal studies have suggested that it is capableof reversing atherosclerosis. Higher vitamin C levels have been linked tolower risk for cataracts, certain cancers, cardiovascular disease, stroke, asthmaand obstructive pulmonary disease. There is a strong rationale that vitaminC may reduce risk for cardiovascular disease via several mechanisms,including inhibition of oxidation of LDL and improvement in functionof the layer of cells which line the blood vessels and heart (the endothelium).
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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 atthe doses usually taken.