Nutritional Needs in Hot Environments Applications for Military Personnel in Field Operations (1993) / Chapter Skim
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7. The Effect of Excercise and Heat on Mineral Metabolism and Requirements
7. The Effect of Excercise and Heat on Mineral Metabolism and Requirements
Pages 117-136
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From page 117... ...
that individuals engaged in strenuous exercise have a higher requirement for some minerals compared to sedentary individuals due to increased rates of urinary and sweat losses of select minerals and (b) that the perceived inadequate intake of some minerals results in a lowering of endurance capacity and ultimately may lead to the development of some disease states.
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From page 118... ...
This hypothesis would be consistent with the observation that exercise can result in increased rates of tissue lipid peroxidation (Davies et al., 1982~. Although the above observations suggest that selenium metabolism may be influenced by exercise, to date there is no compelling evidence that selenium supplementation is necessary for i 1989; Lang et al., 1987~.
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From page 119... ...
This increase in serum chromium was still evident 2 hours after the completion of the run, and urinary chromium loss was elevated twofold on the run day compared to non-run days. Basal urinary chromium excretions have been shown to be lower in individuals routinely engaged in strenuous activity compared to sedentary controls (Anderson et al., 1988)
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From page 120... ...
High levels of physical activity have been suggested to cause "sports anemia" (typically defined as a drop in hemoglobin concentration, hematocrit, and red~blood cell count; Balaban et al., 1989; Yoshimura, 1970~. The phenomenon of sports anemia has been associated with increased erythrocyte destruction, depressed iron absorption, increased sweat loss of iron, and gastrointestinal blood loss (Dressendorfer et al., 1991; Ehn et al., 1980; Frederickson et al., 1983; Paulev et al., 1983; Puhl et al., 1981; Stewart et al., 19841.
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From page 121... ...
Given that prolonged exposure to a regimen of strenuous exercise and/or exposure to conditions resulting in high rates of sweat loss is associated with marked changes in zinc metabolism (see below) , the potential negative effects of excess iron supplementation are clear.
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From page 122... ...
However, by day 1 postrace, zinc concentrations were back to control levels. The observation that plasma zinc concentrations can increase significantly during strenuous exercise has since been verified by numerous investigators (Dressendorfer et al., 1982; Lukaski et al., 1984; Ohno et al., 1985; Van Rij et al., 19861.
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From page 123... ...
The mechanisms underlying the development of exercise-induced hypozincemia are presumably multifactorial and may include impaired absorption of zinc, excessive sweat and urinary loss of the element, and an altered metabolism of zinc (Anderson et al., 1984; Deuster et al., 1989; Miyamura et al., 19871. Although there is considerable debate about the value of plasma zinc in diagnosing zinc deficiency, most investigators agree that prolonged low plasma zinc concentrations are indicative of suboptimal zinc status.
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From page 124... ...
(1970) reported that serum magnesium concentrations in marathon runners immediately following a race were significantly lower than preface values, a phenomenon that was attributed to sweat losses of the element during the run.
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From page 125... ...
Given the recognition that marginal magnesium deficiency can present a significant health risk to an individual, studies are needed that define the functional consequences of exercise- and heat-induced reductions in plasma magnes~um concentrations. EFFECTS OF EXERCISE AND HEAT ON COPPER METABOLISM Acute, strenuous exercise has been reported by several investigators to result in a marked increase in plasma copper concentrations, which has been attributed to an increase in plasma ceruloplasmin concentrations (Haralambie, 1975; Ohno et al., 1984; Olha et al., 19821.
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From page 126... ...
Reasons for the above differences in reported effects of exercise on plasma copper concentrations are various, including differences in copper status of the subjects; type, intensity, and duration of the exercise; physical condition of the individual; and extent of exercise-induced tissue trauma. Presumably, increases in plasma copper occur primarily when there is tissue damage that triggers an acute-phase response.
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From page 127... ...
The simultaneous exposure to hot temperatures would be expected to accelerate the development of a marginal copper condition. CONCLUSIONS Prolonged strenuous exercise can result in marked changes in chromium, copper, iron, magnesium, and zinc metabolism.
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Halliwell 1988 Iron, copper and zinc concentrations in human sweat and plasma; the effect of exercise.
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Dowson 1991 Red blood cell magnesium and chronic fatigue syndrome. Lancet 337:757-760.
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Barnard, and Y Ohira 1977 Physical work capacity and metabolic stress in subjects with iron deficiency anemia.
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Stromme 1975 Serum and erythrocyte zinc concentrations after prolonged heavy exercise.
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Schwartzman, and D Allalouf 1988 Iron deficiency caused by 7 weeks of intensive physical exercise.
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Meen, and S.B. Stromme 1973 Whole blood, serum and erythrocyte magnesium concentrations after repeated heavy exercise of long duration.
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Bray, and W.J. Pories 1986 Changes in zinc metabolism following exercise in human subjects.
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Unfortunately, you can't get animals much more deficient and get meaningful data. We were curious if we could get a dose response using animals fed diets containing less than 50 fig of magnesium per gram, however once pronounced signs of magnesium deficiency occurred, it was difficult to get the males to run.
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