American Journal of Clinical Nutrition, Vol 18, 443-448, Copyright © 1966 by The American Society for Clinical Nutrition, Inc.

Comparisons of Nitrogen, Calcium and Iodine Excretion in Arm and Total Body Sweat

¹ From the U. S. Army Medical Research and Nutrition Laboratory, Fitzsimons General Hospital, Denver, Colorado

In this study comparison of excretions of nitrogen, calcium and iodine, between arm and total body sweat, showed fairly good agreement. Calcium determined from total body sweat ranged from 71 to 76 per cent of that derived by extrapolation from arm sweat, the nitrogen value was 86 to 93 per cent. These values are in better agreement if one takes into account the approximate 7.5 per cent respiratory water loss, which has been included in the calculations of values obtained for total arm sweat. Correlation between the excretion in arm and total body sweat is excellent if all arm sweat samples weighing less than 16 gm. are eliminated. On the basis of these comparisons the calcium losses in sweat reported previously still remain high.

These findings again reaffirm the presence of additional nitrogen, calcium and iodine losses in sweat that have been ignored in many balance studies. Previous calcium and nitrogen balance studies in which equilibrium apparently was attained should be re-evaluated, with consideration being given to these sweat losses, particularly in studies involving men living and working in high environmental temperatures. These sweat losses are probably of little practical significance in studies of fairly inactive subjects living on an air-conditioned ward or in a temperate environment.

It is recommended that in future studies related to sweat collection, the total body sweat procedure should be utilized, wherever possible.