. "8. The Effect of Excercise and Heat on Vitamin Requirements." Nutritional Needs in Hot Environments: Applications for Military Personnel in Field Operations. Washington, DC: The National Academies Press, 1993.
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Nutritional Needs in Hot Environments: Applications for Military Personnel in Field Operations
nicotinamide ingested for 3 days prior to exposure to heat for 2 to 4 days. During the heat exposure, the temperature was 110° to 120°F in the day and 85° to 90°F at night. The vitamin supplementation had no effect on sweat composition, water balance, strength tests, or exercise performance and recovery. Thus, the vitamin supplementation did not affect the rate and degree of acclimatization, the incidence of heat exhaustion, and the ability to perform work in the hot environment (Mayer and Bullen, 1960).
Although studies are equivocal with regard to whether supplementation of several of the B complex vitamins will enhance performance in a hot environment, these studies mainly assessed the effects of a short period of supplementation and a short exposure to exercise in the heat. Because exercise in the heat may increase energy expenditure (Consolazio, 1963), it is possible that a deficiency in B complex vitamins could occur if the dietary intake is not increased accordingly. This is especially true because of the loss of several of the B complex vitamins in sweat. Although the loss is small, if the intake of these vitamins is also compromised, a deficiency could occur. If caloric intake should be increased by work in a hot environment, then the intake of these vitamins would increase accordingly. Thus, for adults, 0.5 mg thiamin per 1000-kcal diet, 0.6 mg riboflavin per 1000-kcal diet, 0.016 mg vitamin B6 per g protein, and 6.6 mg niacin per 1000-kcal diet are recommended (National Research Council, 1989).
Vitamin C (Ascorbic Acid)
Scurvy was identified as far back as the ancient Greeks and Romans. This condition proved to be a scourge to armies, navies, and explorers until the early 1900s when Albert Szent-Gyorgyi first identified a substance that was later named vitamin C and used to prevent scurvy (Sauberlich, 1990). Vitamin C has numerous functions, including the biosynthesis of collagen, catecholamines, serotonin, and carnitine. It also plays a role as an antioxidant and is needed for nonheme iron absorption, transport, and storage (Keith, 1989).
Vitamin C is probably one of the most studied vitamins and one of the most controversial. The popularly believed benefits of vitamin C supplementation range from curing or preventing the common cold to reducing fatigue, wound healing, preventing injury, and enhancing performance capacity (Jaffe, 1984; Keith, 1989; National Research Council, 1989; Pike and Brown, 1984). Vitamin C is widely distributed throughout the body with highest concentrations in the pituitary, adrenals, and leukocytes. Major concentrations also are found in skeletal muscle, brain, and liver.
Ascorbic acid can be measured in the serum or plasma, leukocytes, and urine; however, levels in the plasma or serum are most commonly used (Sauberlich, 1990). Of several groups of athletes studied, most had adequate