Evidence to suggest that the administration of recombinant cytokines can modulate immune function in a desirable manner is limited. Their effectiveness has not been demonstrated in healthy subjects.

Field studies must be based on the results of prior experiments conducted in controlled laboratory and clinical settings. Experimental designs and methods must be validated by pilot tests prior to use.

Total energy intake appears to play the greatest role in nutritional modulation of immune function. Since it has been demonstrated that prolonged energy deficits resulting in significant weight loss have an adverse effect on immune function, emphasis should be placed on the importance of adequate ration intake during military operations to minimize weight loss. Weight loss in the range of 10 percent in operations extending over 4 weeks raisee the concern of reduced physical and cognitive performance and has potential health consequences for some individuals (IOM, 1995).

The nutritional status of soldiers should be optimized prior to deployment, engagement in any exercise or training course, or even brief encounters with anything that would present a potential immune challenge (disease, toxic agent, or environmental stress). When consumed as recommended, operational rations provide adequate energy and macronutrients.

Nutrients that appear to play a role in immune function include protein, iron, zinc, copper, and selenium; the B-group vitamins, especially B₆, B₁₂, and folate; vitamin A and its precursor, β-carotene, vitamins C and E; the amino acids glutamine and arginine; and the polyunsaturated fatty acids. It is difficult, however, to consider the role of one nutrient in isolation. Evidence for a distinct role for vitamin C in immunomodulation remains controversial, and the role of vitamin E has been demonstrated chiefly in the elderly. There is no evidence at this time to indicate that the levels of vitamins A, C and E, or trace elements including zinc, copper, or selenium, are inadequate in operational rations. Increasing or decreasing the consumption of n-6 or n-3 PUFAs or altering their intake ratios may impact immunological function.

The effects of providing supplements of vitamins A, C and E, as well as certain polyunsaturated fatty acids and amino acids, prior to, during, or following infections are virtually unknown in young, healthy adult men. Many questions remain regarding the efficacy of these nutrients in amounts that exceed Military Recommended Dietary Allowance (MRDA) levels. However,