Some nutritional aspects of trace metals.

A brief outline of the known biochemical roles of manganese and chromium is given before the problems of determining human trace metal status are discussed. The factors predisposing to trace metal deficiency are reviewed but particular emphasis is placed upon those which alter the bioavailability of essential trace metals from natural and synthetic diets. This is illustrated by practical examples which show the importance of investigating the bioavailability of the trace metal content of artificial diets used in paediatric care. The results of such studies highlight the need to assess similarly the adequacy of the trace element composition of the many meat substitutes and extenders available currently. Finally, some aspects of trace metal supplementation of intravenous feeding regimens are described.