Nutritional Needs in Hot Environments Applications for Military Personnel in Field Operations (1993) / Chapter Skim
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8. The Effect of Excercise and Heat on Vitamin Requirements
8. The Effect of Excercise and Heat on Vitamin Requirements
Pages 137-172
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From page 137... ...
A review of early studies suggested that vitamins were lost to a significant degree in sweat (Robinson and Robinson, 19541. For this reason, exerciseespecially in hot environments was considered to result in vitamin deficiencies.
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From page 138... ...
This chapter also examines whether exercise in a hot environment will lead to an increased requirement for certain vitamins and whether vitamin supplements will reduce heat stress. Vitamins are classified as either water soluble or fat soluble.
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From page 139... ...
Nijakowski (1966) found that blood levels of thiamin were lower in male athletes compared with a control group, however, it is possible that the lower levels were due to plasma volume expansion in athletes.
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From page 140... ...
Because of the role of thiamin in energy metabolism, it would seem that thiamin deficiency would lead to decrements in exercise performance. However, although thiamin-deficient diets along with deficiencies in other B complex vitamins were shown to adversely affect performance (for review see Van der Beek, 1985)
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From page 141... ...
Van der Beek (1985) reviewed other studies on riboflavin restriction and concluded that riboflavin depletion did not alter work performance on submaximal treadmill tests.
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From page 142... ...
The recommended intake of riboflavin is linked to caloric intake (0.6 mg per 1000 kcal) , and to be safe, this recommendation should be followed by people living and working in a hot environment.
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From page 143... ...
The only information with regard to niacin requirements in a hot environment comes from an early study that found that nicotinic acid was lost in the sweat in significant amounts (100 ,ug per 100 ml; Mickelsen and Keys, 1943~. However, later studies did not agree with this finding (Mitchell and Edman, 1951; Robinson and Robinson, 1954~.
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From page 144... ...
resulted in significant increases in blood levels of PLP that were independent of changes in plasma volume, blood glucose, blood free fatty acid levels, and blood enzyme levels. The authors suggested that the increase in plasma PLP could be due to a release of vitamin B6 from the liver to be used in skeletal muscle to fully saturate glycogen phosphorylase or be used for other critical PLP-dependent reactions (for example, aminotransaminase reactions)
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Cycle ergometry exercise of short duration resulted in a decrease in pantothenic acid levels in the blood, but the levels were unchanged after a long-duration exercise of 4
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From page 146... ...
Because plasma volume was not corrected for, it is difficult to interpret these changes. The effect of pantothenic acid supplementation on exercise performance is equivocal.
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From page 147... ...
Folic acid deficiency has been suggested to be the most common vitamin deficiency in humans and can result in anemia (Keith, 1989~. No studies have assessed the relationship of folic acid status and exercise performance or the effect of folio acid supplementation on performance.
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From page 148... ...
The effect of B complex supplementation on endurance capacity during a treadmill test was examined in physically active male college students (Read and McGuffin, 1983~. The supplement contained 5 mg thiamin, 5 mg riboflavin, 25 mg niacin, 2 mg pyridoxine, 0.5 ,ug vitamin B12, and 12.5 mg pantothenic acid.
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From page 149... ...
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~.
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From page 150... ...
These data provide no evidence to suggest that chronic exercise creates a vitamin C deficiency. Acute exercise appears to increase blood levels of ascorbic acid.
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From page 151... ...
Whether the criterion score reflected an individual's soreness is uncertain. Also, because the exercise used in this study may not have produced significant muscle damage, especially with regard to the generation of free radicals, further study of the relationship of vitamin C and exercise-induced muscle damage is warranted.
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From page 152... ...
, a similar experiment was performed, but blood ascorbic acid levels were also assessed daily during the 10 days of heat stress. Resting blood ascorbic acid levels increased by the same amount in subjects receiving either the 250-mg or the 500-mg vitamin C supplement, and blood levels reached the saturation point between the third and the fifth day.
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From page 153... ...
(1990) developed a sports drink especially for athletes training in hot environments.
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Because no studies have been uncovered that examined the relationship of vitamin K (a vitamin necessary for blood clotting) with exercise performance or heat stress, this vitamin will not be discussed in the following sections.
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From page 155... ...
D3 in the blood; however, blood levels do not fully reflect the extent of storage. Although few studies have examined biochemical status of vitamin D in athletes (Adams et al., 1982; Cohen et al., 1985)
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From page 156... ...
Vitamin E has been shown to function as an antioxidant of polyunsaturated fatty acids in cellular membranes (Machlin and Bendich, 19871. In this role, vitamin E serves as a free radical scavenger to protect cell membranes from lipid peroxidation.
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From page 157... ...
. · Motor fitness tests, cardiorespiratory efficiency during cycle ergometry exercise and bench stepping, and 400-m swim times in male and female trained swimmers given 400 mg daily for 6 weeks (Sherman et al., 1976)
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showed that lipid peroxidation was lower in a group of mountain climbers supplemented with vitamin E Vitamin E may play an antioxidant role in reducing muscle damage from strenuous exercise (Ebbeling and Clarkson, 1989~.
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From page 159... ...
There is no information to suggest that exposure to a hot environment would increase their need above levels recommended by the National Research Council. Since World War I, vitamin C has received popular attention as a nutrient that can reduce heat stress.
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Rubin 1975 Effect of feeding polyunsaturated fatty acids with a low vitamin E diet on blood levels of tocopherol in men performing hard physical labor.
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drink supplementation on athletes training in hot environments.
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Mickelsen, and A Keys 1944b Vitamin C and ability to work in hot environments.
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Keys, A., and A.F. Henschel 1941 High vitamin supplementation (B1, nicotinic acid and C)
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Scherzer, and J Harrison 1985 Effects of pantothenic acid supplementation on human exercise.
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1990 Pantothenic acid.
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From page 166... ...
Van der Beek, E.J., W van Dokkum, J
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We have a few minutes for DR. EVANS: Well, we have one paper that we published in January and two more that are about to be published in which we have looked at the effects of vitamin E supplementations on skeletal muscle damage, circulating and skeletal muscle cytokine (CK)
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From page 168... ...
168 PRISCILLA M CLARKSON effects on vitamin supplementation have been measured just using a gross measure in a VO2 ma'` .
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VITAMIN REQUIREMENTS IN THE HEAT 169 pen to recall whether he assessed what the vitamin C status was before he did the supplementation?
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They don't drink milk and they don't see the sun very much and it may be associated with a profound muscle weakness due to a calcium metabolism problem.
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VITAMIN REQUIREMENTS IN THE HEAT 171 done any studies and looked at the types of microbes that are in the GI tract, the possibility of infection (subclinical infections) that occur in long-distance runners?
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