Facts about Antioxidant 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
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
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
- 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.