β carotene prevents free radical formation by quenching singlet oxygen, a highly reactive form of oxygen. Vitamin C is another free radical scavenger which deactivates free radicals. It works specially in the plasma, lung fluid, aqueous humour and interstitial fluid. It can increase white blood cell activity; play important roles in the biochemistry of antibodies, prostaglandin E 1 , B and T lymphocytes, and interferon. Vitamin E also scavenges free radicals in the blood along with β carotene and vitamin C. Moreover, vitamin E is essential to protect against some of the ill effects of smog and smoke. In relation to other nutrients vitamin E protects vitamin A from being destroyed in the body.
Vitamin C is the most powerful reducing agent known to be present in living tissues. Vitamin C deficiency produces scurvy. It is a cofactor in numerous biological processes. Vitamin C and molecular oxygen are essential for the conversion of proline to hydroxyproline, dopamine to noradrenaline . Vitamin C is also essential for the synthesis of adrenal steroid hormones. Vitamin C is important in the defense against infection and studies shown that vitamin C is important for the normal functioning of T-lymphocyte and leukocyte. Ascorbic acid has some antiinflammatory activity and protects cells against oxidation of essential molecules. In high doses, (1-2 g daily) ascorbic acid increases iron absorption.
vitamin E seems to be as a defense against oxidative stress and lipid peroxidation. In most cell membranes there is one molecule of tocopherol for every 1000 lipid molecules. Tocopherol mops up peroxide radicals and then needs a supply of reduced hydrogen to restore the steady-state situation. This is usually supplied by ascorbic acid or reduced glutathione.
Dosage & Administration
Vitamin C is generally a safe drug for human use in normal doses. Larger doses may lead to gastrointestinal tract upset and renal stone formation.
Vitamin E is considered safe even in large doses. Doses over 800 mg may cause diarrhoea, abdominal pain or cramps, fatigue and reduced resistance to bacterial infection and transiently raised blood pressure.