Electrolyte loss in sweat and iodine deficiency in a hot environment

The authors studied electrolyte loss from profuse sweating in soccer-team p layers and evaluated the relationship between this source of iodine loss an d iodine deficiency. Thirteen male soccer-team players and 100 sedentary st udents from the same high school were evaluated for 8 d, during which the p layers were training. The authors analyzed 208 sweat samples to determine l osses of iodine, sodium, potassium, and calcium in sweat. Excretion of urin ary electrolytes by the subjects was also measured. The mean losses of iodi ne, sodium, potassium, and calcium in sweat following a 1-hr game were 52 m ug, 1,896 mg, 248 mg, and 20 mg, respectively; the ratios of sweat loss to urinary daily loss of the four electrolytes were 0.75, 0.2, 1.88, and 0.92, respectively. Urinary iodine was significantly (p <.02) lower than the nor mal level of 50 <mu>g/gm creatinine in 38.5% of the soccer players, compare d with 2% of the sedentary students. Forty-six percent of the players had G rade I goiter, compared with a mere 1% of the sedentary students (p <.01). The results of the study suggest that loss of iodine through profuse sweati ng may lead to iodine deficiency, and loss of electrolytes through sweating may have a dietary significance for heat-stressed individuals or for indiv iduals who perform heavy workloads.