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The effect of heat stress and high-fluoride intake through water containing up to 2.67 ppm F on gastrointestinal function was studied in two different groups of healthy male subjects (soldiers). In one group the study was conducted for 60 days and in the other group for 24 months on a longitudinal basis when they moved to a desert area. A significant increase in body weight was seen only in the longer term study. No significant change in blood hemoglobin or total plasma protein was noted in either the shortterm or the long-term study. There was a significant increase in blood albumin level on the 15th day. The A:G ratio was significantly lower on the 60th day as compared to the ratio on the 15th day. The subjects had more than 30% excretion of D-xylose in 5 hr during all the test periods, thereby signifying unaltered intestinal absorption.

The results indicate that healthy natives of tropical areas who are well acclimatized to heat stress do not suffer from intestinal malabsorption on induction to a desert area. Even higher levels of fluoride intake through water do not appear to affect protein metabolism and intestinal absorption when adequate nutrition is maintained.