RESUMO
An excess of free-radical production has been linked to many diseases and to the ageing process. Oxidant by-products of normal metabolism can cause extensive damage to DNA, protein and lipid. Exposure to ultraviolet light, cigarette smoke and other environmental pollutants may also increase the free radical burden. The accumulation of unrepaired oxidative damage products is likely to be a major factor in cellular ageing. Many repair processes are available to the cell, including enzyme and structural defences. The large group of natural antioxidants is also part of a protective mechanism. High consumption of fruit and vegetables in the diet is associated with a lowered risk of degenerative diseases. At present, however, there are few data to support the routine use of exogenous antioxidants to prevent and treat these diseases.
