RESUMO
Free radicals are normally produced as a by-product of cellular metabolism. Free radicals are capable of killing bacteria, damage biomolecules, provoke immune response, activate oncogens, cause atherogenesis and enhance ageing process. However, in healthy conditions nature has endowed human body with enormous antioxidant potential. Subtle balance exists between free radical generation and antioxidant defence system to cope with oxidative stress by various enzymes and vitamins at cellular level which prevent the occurrence of disease. However, factors tilting the balance in favour of excess free radicals generation lead to widespread oxidative tissue damage and diseases. Therefore, trouble starts when there is an excess of free radicals and the defence mechanism lags behind. Overwhelming production of free radicals in response to exposure to toxic chemicals and ageing may necessitate judicious antioxidant supplement to help alleviate free radical mediated damage.