Influence of Altitude Changes on Intestinal Iron Absorption

The absorption of iron in the form of ferrous sulfate was studied in 82 subjects and under various conditions of altitude exposure. Intestinal absorption of iron increased during the first days of exposure to an altitude of 14,900 feet and reached a maximum at the end of a week. It was less marked 4 weeks later. Iron absorption decreased in natives of high altitude brought down to sea level, reached a minimum in 3 weeks, and then returned to normal within 16 months. Studies on the recovery of iron in feces confirmed the changes that were interpreted on the basis of the amount of iron appearing in the red blood cells plus the iron that presumably reached the circulating plasma but was not used in red cell formation. The possible significance of failure in some cases to recover a small fraction of the total iron that was administered is discussed.