The detenmnation of optimal nutritional status has traditionally been based upon generalized parameters such as weight gain and body fat levels. Vitamin and mineral requirements were often related to the intakes needed to prevent overt signs of deficiency diseases such as beriberi or scurvy. However, in the past decade or so, there have been intensive investigations to determine the subtle changes in physiological functions associated with marginal micronutrient intakes. There is a growing consensus that immune system activities are very sensitive indicators of micronutrient status. During...