Excretion of Sodium, Potassium, Magnesium and Iron in Human Sweat and the Relation of Each to Balance and Requirements

The results of this study show that a considerable quantity of sodium, potassium, magnesium and iron are lost in sweat of men during 16 consecutive days' exposure to environmental temperatures of 100°F. During a 7.5-hour collection period, the sweat excretions averaged 0.601 gm/hour for sodium, 0.125 gm/hour for potassium, 2.3 mg/hour for magnesium and 0.13 mg/hour for iron. Very small quantities of phosphorus are excreted in sweat, averaging between 0.45 to 0.81 mg/hour. In the past, with the exception of sodium, very few investigators have recognized the fact that the mineral losses in sweat could be appreciable and as a result these losses have, all too frequently, been neglected in computing mineral balance. This could result in misinterpretation of the data, especially under conditions of profuse sweating. The total mineral loss should include the mineral loss in sweat. This in turn would help in estimating more realistically the minimal daily allowances of minerals.