Antioxidant Vitamins (Vit E, β Carotene, Vit C) In Prevention of Cardiovascular Disease and Cancer

ANTIOXIDANT VITAMINS (VIT E, β CAROTENE, VIT C) IN PREVENTION OF CARDIOVASCULAR DISEASE AND CANCER

Antioxidants are believed to quench free radicals. Free radicals are atoms or molecules with ‘singlet’, i.e. unpaired electron which makes them highly reactive. Oxidative free radicals are generated by metabolic reactions—create a chain reaction leading to membrane lipid peroxidation, DNA damage, etc. Free radical oxidation has been implicated in atherosclerosis (oxidized LDL is more atherogenic), cancers, neurodegenerative diseases and inflammatory bowel diseases. Many endogenous and dietary compounds like superoxide dismutase, ferritin, transferrin, ceruloplasmin, α tocopherol, β carotene and ascorbic acid have antioxidant and free radical scavenging properties. On this theoretical basis supported by some epidemiological observations, cohort studies and prospective trials β carotene, vit C and especially vit E have been claimed to protect against atherosclerosis leading to coronary artery disease as well as many types of cancers (lung, breast, mouth, skin, esophagus, stomach, etc.). As a result, vit E and others are being aggressively promoted and many physicians are prescribing them for prophylaxis of these conditions. Learning from mass media, people on their own also are consuming them on a large scale. However, the evidence of a beneficial effect is highly contradictory.

Several large observational studies (involving tens of thousands of subjects) and their metaanalysis have failed to demonstrate any benefit of antioxidant vitamins in terms of cardiovascular event/cancer prevention in well nourished population. On the other hand, there is some indication of increased risk of CHF with >400 mg/day α tocopherol and increased risk of hip fracture among postmenopausal women with high dose of vit A. Therefore, it would be well advised to adopt a healthy lifestyle, viz. eating sufficient fruits and vegetables, doing regular exercise, avoiding overweight and smoking, rather than consuming antioxidant medications.

A large number of antioxidant proprietary preparations (ANTOXID, CAROFIT, GLACE, VITOXID, REVOX, CARNITOR, CARNIVITE, etc.)

containing widely variable amounts of βcarotene, vit A acetate, vit E, vit C, selenium, zinc, copper, manganese, carnitine (a substance synthesized in liver and kidney, and involved in intracellular transport of longchain fatty acids) are briskly promoted and consumed, but with no credible evidence of benefit, and may be some potential harm.