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Protein requirements in tropical countries: nitrogen losses in sweat and their relation to nitrogen balance

Published online by Cambridge University Press:  09 March 2007

Ann Ashworth  and
A. D. B. Harrower
Ann Ashworth
Affiliation:
Medical Research Council, Tropical Metabolism Research Unit, University of the West Indies, Jamaica
A. D. B. Harrower
Affiliation:
University of Edinburgh Medical School, Edinburgh
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Abstract

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1. An experiment was undertaken to determine whether high rates of sweating in a tropical climate affect protein requirements by increasing the total nitrogen losses from the body.

2. Six fully acclimatized volunteers were given a diet supplying 50 g protein (= 8 g N) daily. They performed strenuous physical work of a normal nature for an average of 6½ h a day for two 5-day periods. During control periods the subjects took minimal exercise and lived in a cool environment. N balance was measured throughout.

3. Rates of sweating were measured by weighing. Whole body sweat was collected and the concentrations were measured of nitrogen, sodium and potassium. During 6½ h work approximately 3 l. of sweat were lost, containing on average 0·49 g N, 64 m-equiv. Na and 22 m-equiv. K.

4. The N concentration in sweat was 0·20 mg/g, which is lower than that found by most other workers. It is suggested that acclimatization is an important factor in reducing N loss by sweating.

5. There was a marked decrease in urinary Na excretion during sweating, which compensated fully for the loss of Na in sweat. Renal compensation for loss of K was less efficient.

6. Because the total N loss in sweat was small, it was not possible to establish with certainty whether it was compensated for by a reduced renal excretion of N. However, after the initial period the subjects were in N balance in spite of the relatively low protein intake.

7. It is concluded that there is no evidence to suggest that heavy sweating under natural conditions in a tropical climate causes a significant increase in protein requirements.

Type
Research Article
Information
British Journal of Nutrition , Volume 21 , Issue 4 , December 1967 , pp. 833 - 843
Copyright
Copyright © The Nutrition Society 1967

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