The measurement of food iron absorption in man. A methodological study on the measurement of dietary non-haem-Fe absorption when the subjects have a free choice of food items.

1. The present study was considered as a first step to develop a method to measure food iron absorption from realistic common meals prepared and consumed by the subjects themselves in their own homes. The absorption of Fe from the meals was measured by means of the extrinsic-tag method modified to allow for a free choice of food items. 2. The mean Fe intake was 2.79 mg and the mean Fe absorption approximately 0.30 mg. The Fe status of the subjects corresponded to 31.5% absorption from a reference dose solution containing 3 mg elemental Fe as ferrous ascorbate. The variation in food Fe absorption obtained in this field study was found to be of the same magnitude as that obtained in studies performed under more controlled conditions as in the laboratory. 3. The conclusion was drawn that the proposed method could be used in realistic field studies aimed at, for example, explaining or preventing a high prevalence of deficiency. A suffciently long run-in period and a careful instruction of the subjects was considered essential for the design of future field studies.