Antioxidants are believed to quench free radicals. Free radicals are atoms or molecules with ‘singlet’, i.e. unpaired electron which makes them highly reactive.
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.
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