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tion problems, and coping with threats and emergencies. A group led by Sargent and Johnson at the University of Illinois spent considerable time and effort in the 1940s and 1950s working on undernutrition (as well as more normal nutrition). They established fundamental physiological, nutritional bases for an all-environment survival ration (Sargent and Johnson, 1957):

  1. Maximal feasible kcal content provided by a balanced mixture of first-class protein, carbohydrate, and fat. The goal should be 2,000 kcal per man per day, of which protein should provide 15 percent of kcal, carbohydrate 52 percent of kcal, and fat 33 percent of kcal.

  2. Water allowance as liberal as possible, with a goal of three quarts per man per day for hot weather, and no less than one quart per man per day under any circumstances.

  3. An optimal osmotic intake, neither too large nor too small. The goal should be 700 milliosmols per day, provided by the sum of protein and minerals.

  4. Within limits set by the recommended proportions of protein, carbohydrate, and fat, minimal ketogenicity, minimal specific dynamic action, and maximal water of oxidation.

Although the focus was on adequate carbohydrate supply during the 1940s and 1950s, largely to avoid the debilitating effects of ketosis, there was also concern about adequate protein and preservation of body tissue including skeletal muscle mass. Mitchell and Edman (1949, 1951) said about protein:

Considering all evidence, it may be concluded that protein requirements may be slightly increased in the tropics by some 5 to 10 grams daily ... Laboratory experiments show that protein requirements may be increased slightly by (a) a stimulation of tissue catabolism if pyrexia occurs, and (b) by sweat losses of nitrogen uncompensated by diminished losses in the urine.

Consolazio and Shapiro (1964) found in the summary of their studies of men exercising under different climatic conditions that protein intake in the hot climate exceeded the National Research Council's recommended allowance of 100 g per day. In contrast to the conclusion of Mitchell and Edman (1949, 1951), Consolazio and Shapiro felt that increased protein intake in the heat was due not to an innate desire for protein, but to the relatively greater caloric intake. Recently, Paul (1989) suggested that because protein and amino acids contribute from 5 to 15 percent of energy for prolonged exercise—with the higher values perhaps associated with glycogen depletion—adequate protein intake is important when exercising in the heat. He pointed out that urine and sweat urea increase during prolonged, relatively intense exercise. Nevertheless, there appears to be no evidence that protein

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