Free radicals are a normal and natural by-product of the energy producing biochemical reactions in the mitochondria of each and every cell in the body. Like other waste products, however, free radicals can cause problems if they're produced in excessive quantities which cannot be safely disposed of. In the case of excessive free radicals, the problems caused are damage to the very cells and molecules of the body; damage which spreads rapidly through chain reactions as the damaged cells and molecules themselves become free radicals. Left unchecked, these chain reactions can accelerate the process of aging within the body and even contribute to the development of the characteristic diseases of degeneration - heart and circulatory problems, age-related cognitive and visual impairment, and even cancer.

The so-called superoxide free radicals are a particularly pernicious example and are released upon the metabolism of oxygen within cells, literally with breath we take Superoxide free radicals react with other by-products of energy production to form hydroxyl, the most damaging free radical of all, and to attack the mitochondria of the cells themselves.

Since it is the mitochondria which ultimately produce the energy for all the body's vital reactions, mitochondrial damage due to free radicals can only mean the production of less and less energy and the gradual deterioration and degeneration of the entire organism. It has even been argued that the rate of mitochondrial damage is the key to the rate of ageing itself.

The antioxidant enzymes, superoxide dismutase, catalase and glutathione, are the body's first line of defence against superoxide free radicals and work in a closely complementary fashion. It is dismutase that first breaks down the superoxide free radicals into oxygen and hydrogen peroxide, but catalase is then required to break down that hydrogen peroxide into plain oxygen and water. Further free radical attack would otherwise turn the hydrogen peroxide into the dreaded hydroxyl which once formed cannot be neutralized by any enzyme.

So far, so good, but the problem is that catalase is water and not fat soluble and is therefore ineffective at protecting those vital parts of the cell, such as the membranes, which are actually formed of fat. For this the body also needs glutathione to soak up and neutralise any rogue hydrogen peroxide molecules in these areas. Glutathione also acts directly against any free radicals attacking the fatty membranes themselves.

Each of these enzymes is formed by the body from the amino acids in the proteins in your diet and each is needed for the others to function correctly. This holistic functioning of the body is also reflected in the dietary requirements for the successful production of the enzymes. As well as a good supply of first-class protein, ie that containing each of the eight essential amino acids, a wide variety of vitamins and minerals are required to allow optimal levels of enzyme manufacture.

In particular, vitamin C and those of the B complex, together with trace minerals such as manganese, zinc, copper, sulfur and selenium appear particularly important. But it can never be stressed too strongly that the body functions holistically and a deficiency or malfunction of any one of its myriad of incredibly complex and interdependent systems is almost invariably part of a more general malaise.

Damage to cells once done appears to be irreversible. That's why although there may be ways to slow down the aging process, nobody's yet figured out how to reverse it. By the time you see the visible evidence of nutritional deficiencies it's probably already too late.

So in seeking to ensure an adequate supply of anti-oxidant enzymes, the only sensible policy to pursue is to ensure that the diet is rich in all essential nutrients.

Unfortunately that's easier said than done in our "advanced" Western civilisation of these days. Intensive over exploitation of farm soils, the modern prevalence of highly refined grains, and the treatment of fruits and vegetables with preservatives, dyes, pesticides and even radiation is a proven disaster for vitamin and mineral retention in food.

This does not for a moment mean that it's not worth trying to eat a diet rich in anti-oxidants - that's to say a diet which includes lavish servings of fresh fruit and vegetables. But it does mean that a regime of sensible anti-oxidant supplements may be a wise precaution, and its one increasingly adopted by many well informed individuals, including physicians, as a sensible and cost effective form of health insurance.