Volume and composition of hand sweat of white and black men and women in desert walks

Abstract

Many investigators have sought, but failed to find, ethnic differences in the number and regional distribution of active sweat glands. In this study measurements have been made of sweat secreted on one hand and also on the whole body of Whites and Blacks walking in desert heat. Whites numbered 31 men and 27 women, ages 30 to 88 years; there were 21 Black men and 31 Black women, ages 16 to 61 years. Each walked on three occasions for 1 hour at a rate that required an oxygen consumption of about 40% of aerobic capacity. Ambient temperature ranged from 32 to 44 degrees C in 1979 and 1980; means were 38.4 degrees C in 1979 and 36.7 degrees C in 1980. There was no sweat in the gloves of many Blacks; this was true of only a few Whites. Volume of body sweat increased in both races with rate of walking; volume of hand sweat increased more in Whites than in Blacks. The Mann-Whitney test revealed that volumes of hand sweat were significantly greater for Whites than for Blacks. It was concluded that in desert walks most Whites and few Blacks sweat freely on their hands. In samples of hand sweat, Na+, K+, and Cl- were determined. Concentrations of each ion varied widely in both races, and were unrelated to race. Concentrations of Na+ and Cl- generally are somewhat higher in hand sweat than in body sweat; concentrations of K+ are much higher. It follows that the values for concentration of Na+ and Cl- reported in Table 3 probably are somewhat higher than would have been found in body sweat, and concentrations of K+ are probably much higher.

Racial Differences in Urinary Potassium Excretion

“…Racial differences in sweat K have not been well studied; a study of hand sweat of white and black individuals who walked in a desert did not reveal a racial difference in sweat K concentration, but the volume of hand sweat (which has a higher concentration of K than body sweat) was higher, not lower, in white than in black individuals. 28 Black-white differences in stool excretion could possibly account for racial differences in urinary K excretion, but this has also not been well studied. In two small studies (one in South Africa and one in the United States), urinary and stool K excretion were both higher in white than in black individuals on uncontrolled diets, but the ratio of fecal to urinary K was higher in black than in white individuals.…”

Gastrointestinal and renal excretion of potassium in African–Americans and White Americans

“…Aloia has shown that black women have greater total body Na þ content and that the excess body Na þ compared with White women is localized to skeletal tissue [38]. Finally, it should be noted that there is no racial difference in the loss of K þ by sweat [27,39].…”

Decreased Na+,K+,2Cl− cotransport and salt retention in Blacks: a provocative hypothesis

“…Second, in humans, sweat glands contribute up to 50% of total salt and water excretion during extensive exercise and psychoemotional activity [9]. Third, in a hot environment, the function of sweat glands is suppressed in Blacks compared to Whites [10]. Fourth, salt retention by sweat glands results in augmented salt-loading of renal distal tubules, which in turn leads to apical membrane depolarization and enhanced K þ secretion [11].…”