Nutritional Needs in Cold and High-Altitude Environments Applications for Military Personnel in Field Operations (1996) / Chapter Skim
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13 Effects of Cold and altitude on Vitamin and Mineral Requirements
13 Effects of Cold and altitude on Vitamin and Mineral Requirements
Pages 215-244
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From page 215... ...
However, a superficial perusal of the published literature on the effects of altitude demonstrates that the preponderance of research efforts has been directed to understanding the impact of a limited oxygen supply on human performance. With respect to nutrition, there has been only a modest effort to determine energy intake and to determine the preferred mix of energy derived from carbohydrate, fat, and protein.
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From page 216... ...
Each micronutrient intake goal has been derived by the author from a systematic reading of the relevant published literature and from personal consideration of widely-accepted, general nutrition principles. Construction of the micronutrient intake goals assumes that the individuals using it are in generally good health and nutrient status prior to beginning the expedition or maneuver.
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From page 217... ...
Therefore, for the construction of the micronutrient intake goal, an estimated average energy intake of 4,500 kcal/d will be assumed in order to keep the personnel in energy balance. Any deficit between energy intake and expenditure must result in loss of body tissue.
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From page 218... ...
Lui and Roels (1980) reported that vitamin A deficiency did not affect energy production by the Krebs cycle, but glycogen synthesis from lactate and glycerol appeared to be slowed down.
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From page 219... ...
Therefore, the suggested micronutrient intake goal for vitamin A is set at the RDA and MRDA level of 1,000 fig RE (Table 13-1~. This recommendation is in contrast to the Thomas et al.
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From page 222... ...
Author's Recommendation The exposure of the skin to ultraviolet radiation, coupled with a possible release of vitamin D stores from mobilization and utilization of fat stores during prolonged and strenuous physical exertion coupled with inadequate energy intake, should provide sufficient vitamin D to meet nutritional needs in both cold and high-altitude environments. In addition to sunlight, the inclusion of vitamin D-supplemented milk powder in the diet should provide
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From page 223... ...
. For these reasons, the suggested micronutrient intake goal for vitamin E is set at 400 mg octocopherol equivalents (ATE)
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From page 224... ...
Hence, it is suggested that the micronutrient intake goal for vitamin K be set at the RDA level of 70 to 80 fig, which is commensurate with what is found normally in foods. WATER-SOLUBLE VITAMINS All of the water-soluble vitamins, with the exception of folio acid and vitamin C, are intimately involved in the oxidation and conversion of food to energy at multiple steps leading up to and in the functioning of the Krebs cycle (see Hunt and Groff, 1990~.
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From page 225... ...
It is also necessary for the conversion of pyruvate to acetyl-CoA, in the hexose monophosphate shunt, and in the synthesis of fatty acids from acetyl-CoA. A deficiency of niacin could impair glycolysis and the Krebs cycle, whereas excessive niacin supplementation may suppress the release of free fatty acids from adipose tissue through decreased lipolysis, resulting in a decreased availability of a major fuel source for utilization during strenuous exercise (Bulow, 1981; Carlson et al., 1963~.
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From page 226... ...
For this reason, the suggested micronutrient intake goal for niacin is set at 20 mg/d, which is between the RDA and the MRDA (Table 1311. This amount should be sufficient to prevent a deficiency of the vitamin but not so high as to inhibit release of fatty acids.
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From page 227... ...
did not appear to affect vitamin B6 status, as determined by concentrations of PLP in serum and erythrocytes. There was an increased intake of vitamin B6 during Operation Everest II (Rose et al., 1987~.
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From page 228... ...
Due to the unknown effects of supplemental vitamin B6 on hemoglobin oxygen binding affinity, no increased intakes of vitamin B6 above RDA or MRDA levels have been included in the suggested micronutrient intake goal (Table 13-11. vitamin Be Functions Vitamin B,2 is needed for the conversion of methylmalonyl-CoA into succinyl-CoA, which enters directly into the Krebs cycle.
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From page 229... ...
Due to the low toxicity of this vitamin (NRC, 1989) and due to its essentiality in energy production, 10 mg of pantothenic acid per day is recommended in the suggested micronutrient intake goal (Table 13-1~.
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From page 230... ...
Pernicious anemia is caused by decreased absorption or inadequate intake of vitamin By. It is suggested that the micronutrient intake goal for folic acid be set at 400 ,ug/d (Table 13-11.
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From page 231... ...
Hasunen and Pekkarinen (1976) reported daily dietary intakes of only 17 to 34 mg of vitamin C by Finnish Skolt children.
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From page 232... ...
(1950) reported a decreased urinary excretion of ascorbic acid when subjects were repeatedly exposed to simulated altitudes of 5,450 m (17,869 ft)
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From page 233... ...
Nevertheless, it is possible that supplemental vitamin C may have protective or beneficial effects on the pulmonary as well as the immunological systems for those engaged in strenuous physical exertion such as occurs when working at high altitudes or in the cold. Author's Recommendation Due to the relatively low toxicity of vitamin C, the role of vitamin C in the synthesis of adrenal hormones, its possible role in maintaining core and surface body temperature, its apparent beneficial effects in pulmonary function, and its possible role in maintaining immune function, it is suggested that the micronutrient intake goal be set at 250 mg/d for prolonged expeditions or maneuvers in cold or high-altitude environments (Table 13-1~.
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From page 234... ...
Author's Recommendation Because intakes of calcium have been reported to be near that suggested by the RDA and there have been no indications of an inadequate intake or adverse change in status of calcium during the 9-wk period at high and extreme altitude, there is no basis for recommending the micronutrient intake goal of calcium above the current RDA and MRDA levels of 800 to 1,200 mg/d (Table 13-1~. Phosphorus Functions Phosphorus is required for bone formation and integrity, with approximately 85 percent of the total phosphorus in the adult body localized in the bones (NRC, 1989~.
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From page 235... ...
Author's Recommendation Because there has been no indication of abnormally low intake or excessive excretion of phosphorus in the cold or at high altitudes, there is no justification for recommending the micronutrient intake goal for phosphorus above the RDA and MRDA level of 800 to 1,200 mg/d (Table 13-1~. Magnesium Functions Magnesium is essential for the production of ATP and for numerous other enzymatic reactions.
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From page 236... ...
Authors Recommendation Due to the essentiality of magnesium in energy production, its low toxicity, and the observed low intake during the On Top Everest '89 expedition, the suggested micronutrient intake goal for magnesium is set at 400 mg/d, which is at the upper range set by the MRDA (Table 13-1~. Iron Functions Iron is an essential constituent of hemoglobin and myoglobin as well as several enzymes.
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From page 237... ...
. The lack of decline in serum ferritin indicates that there was an adequate intake of iron and of iron stores to prevent onset of iron deficiency brought on by the altitudeinduced polycythemia.
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From page 238... ...
Due to the high suggested dose of vitamin C, which enhances absorption of nonheme iron, the suggested micronutrient intake goal level of iron should be sufficient to prevent onset of an iron deficiency. Zinc and Copper Functions Both zinc and copper are required as enzyme cofactors, with substantial amounts of zinc stored in bone and muscle tissue (NRC, 1989~.
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From page 239... ...
Due to consistently low intakes and periodic high excretions of zinc during the On Top Everest '89 expedition, it is suggested that the micronutrient intake goal of zinc be provided in the foods actually consumed by soldiers or others working in the cold or at high altitudes. This increased amount of zinc is not high enough to adversely affect copper status (NRC, 1989~.
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From page 240... ...
Duration of this study must be sufficient to allow for changes in nutrient status if any, to occur; that is, a range of 3 to 4 months. Whereas simulated high altitudes, such as those produced by the excellent studies conducted during Operation Everest II, can be used to investigate the effects of low oxygen pressure on nutrient intakes and changes in status, such hypobaric chamber experiments cannot duplicate the massive expenditures of energy, the prolonged exposure to cold, and the psychological concerns regarding danger and isolation that occur during actual expeditions to high altitudes.
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From page 241... ...
Havel, and L Ekelud 1963 Effect of nicotinic acid on the turnover rate and oxidation of the free fatty acids of plasma in man during exercise.
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From page 242... ...
Mazess, R.B., and W Mather 1 976a Bone mineral content of north Alaskan Eskimos.
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From page 243... ...
Cymerman 1987 Operation Everest II: Effects of a simulated ascent to 29,000 feet on nutrition and body composition. Technical Report T1S-87.
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From page 244... ...
Natick, Mass.: U.S. Army Research Institute of Environmental Medicine.
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