Free radicals are substances, generally pollutants, that bind to constituents in cells and prevent proper function. Anti-oxidants bind to the free radicals before they can do their damage. It is important to find a good vitamin supplement, or set of supplements. Vitamins should be derived from natural sources. The proper dosage is also of importance.
Proper amounts differ per individual.
Again, check with your health care provider about this. There is no substitute for proper diet in the maintenance of health. But vitamin supplementation is necessary to bring our nutritional standards back to the level of our forefathers.