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be paid to those factors that will encourage adequate ration consumption to minimize the potential for reduced nutrient intake over time.

It is also fitting to consider the quote from Dill (1985) cited by Buskirk:

In the hot desert even a well trained human can sprint only about half the distance one would guess before collapsing. One should respect the incredible intensity of the desert, protect oneself with shade, spare water, slow movement, equally-minded partners, then enjoy and relish its beauty.

Buskirk continues:

Unfortunately, military personnel engaged in combat or under the threat of combat may not have the luxury of contemplating beauty, but they nevertheless must deal with the "incredible intensity of the desert."

Vitamins

There has been considerable research dealing with the effects of temperature and exercise on vitamin requirements, particularly requirements for the B vitamins and vitamin C. A review of this published literature was presented at the workshop by Priscilla M. Clarkson (Chapter 8).

B Vitamins

Although there is limited evidence of small increases in the loss of some B vitamins in sweat during work in hot environments, these losses are not sufficient to increase the requirements beyond the intakes recommended in the current MRDAs. Because the vitamins thiamin, riboflavin, niacin, and vitamin B6 are important in energy metabolism, their intake should be related to energy intake. As noted earlier, the MRDAs are based on the RDAs and are revised periodically to reflect the regular revision of the RDAs. For these vitamins, the current MRDAs (see Table 1-1) are based directly on the amounts given in the ninth edition of the RDAs (NRC, 1980) (vitamin B6) or are based on the amounts given in the ninth edition of the RDAs with a higher assumed caloric intake (thiamin, riboflavin, and niacin). The MRDAs are currently undergoing revision to reflect the changes in the tenth edition of the RDAs (NRC, 1989b), current scientific knowledge, and the demands of military tasks. Thus, the recommendations contained in the present MRDAs for these B vitamins appear sufficient to satisfy requirements for hot environments as long as the rations are consumed in adequate amounts. Furthermore, consideration can be given to decreasing the MRDAs for these nutrients in the revised edition of this regulation, in keeping with the recommendations of the tenth edition of the RDAs and on the basis of caloric intake.

There is no evidence that the levels of folic acid and B12 required for



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