Vitamin, selenium, zinc and copper interactions in free radical protection against ill-placed iron.

The possible involvement of highly reactive free radicals in the development of disease, particularly cancer and inflammation, and in tissue injury following heart attack, transplant surgery or certain types of chemical poisoning, are currently attracting considerable interest. Although in the healthy body, carefully controlled reactions catalysed by enzymes continue to be the rule, it now appears more and more likely that in ill-health, non-enzymic free-radical oxidation processes catalysed by iron can sometimes play a critical, if not a central, role. Of course to nutritionists, such interest in non-enzymic oxidations is nothing new. The fact that foodstuffs generally deteriorate on storage, not only in terms of palatability but also in nutritional value, has long been the bane of the food industry. Papers such as ‘The effect of heat and aeration upon the fat-soluble vitamine’ (Hopkins, 1920), ‘Inactivation of vitamin A by rancid fat’ (Powick, 1925), ‘The autooxidation of fats with reference to their destructive effects on vitamin E’ (Cummings & Mattill, 1931) and ‘Vitamin E in iron-treated dry rations’ (Waddell & Steenbock, 1931), clearly illustrate the early interest in this area. By the mid-1940~, in spite of the limited techniques available, much of the ground work had already been laid for what we currently know about free radicals, trace metals and vitamins in the development of food rancidity. By then, unsaturated fats were known to be particularly susceptible to oxidation by a metal-catalysed, free-radical chain reaction. Oxygen was known to be consumed in the process and when P-carotene was present a fading of the familiar red-orange colour was observed. Various hydroxylated compounds including vitamin E were known to delay the onset of rancidity and the additional presence of vitamin C could delay the onset even further (Golumbic & Mattill, 1941). Now 40 years later many of these oxidation phenomena are being studied again. This time, however, interest is focused more on the eater than on the eaten. It could be said that medicine and biochemistry have caught up with the food industry. ‘We contain unsaturated fat, Fe and 0,: why don’t we go rancid?’ Or put another way, ‘Why doesn’t living matter go rancid until it in turn becomes food? Antioxidants such as propyl gallate or butylated hydroxy toluene are often added to biscuits and other fat-containing foodstuffs to prolong shelf-life. ‘What are the body’s natural antioxidants?’ Such questions are providing much of the impetus for the current surge of interest in the role of free-radical reactions, hydrogen peroxide and what has been variously described as ‘decompartmentalized’, ‘ill-placed’, ‘free’, or