Keywords: Iron, Copper, Zinc, Iodine, Selenium, Diet, Human.

The essential mineral elements are crucial in maintaining 'normal health' in humans, animals and plants. Along with the vitamins, these essential elements occur in minute amounts in the human diet. Despite being essential at parts per million or fractions of parts per million, in some cases there can be too little in the diet. In the human diet, these so-called 'trace elements' that are best characterised are iron, copper, zinc, iodine and selenium. The essentiality of these elements derives from their roles as co-factors in essential proteins and enzymes, the only exception to this is iodine which forms an integral part of thyroxine and triiodothyronine, the biologically-active thyroid hormones. As well as being essential for health, these trace elements can be consumed in toxic quantities and the ratio of essential to toxic levels in the diet can be as low as 5-fold. Much research with animal models of trace element deficiency has produced data that has been used to imply the functions of these trace elements in humans. Similarly, the animal research has been used to inform the recommendations for the adequate levels of trace elements in human diets. Thus the essentiality of trace elements in the diet for human health remains a complex subject in which many questions remain to be answered. Particularly, much research is required to determine what are important dietary interactions between the trace elements which may lead to inadequate functions in the human body. When such knowledge has been derived we will be in a better position to answer the question, "Is there a problem with trace element supply, and does this have consequences to the human population"?

John R Arthur, Rowett Research Institute, Bucksburn, Aberdeen, U.K.

19 Pages, 8 Tables, 24 References.