Iron Metabolism in Human Subjects on Daily Intakes of Less than 5 Milligrams

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Abstract
The iron metabolism of four healthy college girls was studied for periods varying from 3 to 8 months. The greater part of the time the subjects were on a diet adequate in all known dietary essentials except that it contained only 3.5 mg. to 4.5 mg. of iron. A fecal excretion of iron which did not exceed the iron intake did not mean the body was in iron equilibrium. At all times on the low-iron diet the total of fecal, urinary and menstrual iron losses exceeded the intake so that the body was losing iron from its storage depots. The extent of this loss averaged 0.33 mg. of iron daily on an intake of 3.50 mg. When the iron content of the diet was increased to 6.55 mg. by replacing the 750 ml. of milk in the basal diet of three subjects with 116 gm. of lean beef, there was an average daily retention of 2.14 mg. of iron. The iron content of the blood serum decreased consistently and significantly during the low-iron regimen but whenever the intake of iron was increased the serum iron levels rose markedly and then dropped again when the low iron intake was resumed. The results suggest that there is no need for emphasis on amounts of iron exceeding 6.5 mg. daily in the diet of normal young women; emphasis should rather be placed on liberal amounts of other dietary essentials.