Nutrition Reviews, Vol. 55, No. 6 233 Strategies for the Prevention of Iron Deficiency Through Foods in the Household Miguel Layrisse, M.D., and María Nieves García-Casal, Ph.D. June 1997: 233–239 The authors are with the Instituto Venezolano de Investigaciones Científicas, Apdo. 21827 Caracas 1020-A, Venezuela. A portion of the studies reported herein was supported by the National Council of Scientific and Technology Research. Iron deficiency can be caused not only by diets deficient in iron but by poor absorption of available dietary iron. Extrinsically tagging foods with radioiron allows the exact measurement of iron absorbed from heme and nonheme iron foods. It has furthered the study of the effect of enhancers and inhibitors of iron absorption. As a result, we have a greater understanding of why iron deficiency and iron deficiency anemia are prevalent in populations of low socioeconomic status and of which food vehicles and iron compounds are most suitable for iron fortification. Introduction In the 1940s, the measurement of iron absorption by chemi- cal methods existed, 1,2 but in 1951 Moore and Dubach 3 introduced a more physiologic method, incorporating ra- dioactive iron during the life of animals and vegetables. This procedure was not received with much enthusiasm owing to the tediousness of plant culture, the large amount of radioiron necessary for biologic tagging, and the indi- vidual variability of iron absorption, which required the utilization of a large number of subjects for each experi- ment. Only labeled hemoglobin, which is easy to prepare from small animals, was used as a model to measure iron absorption from food. According to the revision carried out by Moore in 1964, 4 of 133 iron absorption tests, 51 were from hemoglobin and only 15 from food of vegetable origin. This sample indicated that iron from animal foods, with the exception of eggs, was better absorbed than iron from food of vegetable origin. At the end of 1969 the results of a collaborative study carried out in Venezuela by the Department of Botany and Medicine of the University of Washington in the United States and by the Department of Pathophysiology of the Instituto Venezolano de Investigaciones Científicas (IVIC) were published. One hundred and thirty-one subjects were tested for iron absorption from six foods of vegetable ori- gin and three foods of animal origin. 5 This study was en- larged with additional tests from seven foods of vegetable origin and five foods of animal origin in 782 subjects di- vided into normal iron status and iron-deficient groups (Figure 1). 6 The previous year Layrisse et al. 7 published a paper on the interaction between foods of animal and vegetable origin given at the same meals with different radioiron. The effect on iron absorption was studied. Results showed that iron absorption from veal muscle was not affected by either black beans or corn, but the veal muscle increased the iron absorbed from vegetable foods. This study, utiliz- ing intrinsically labeled foods of animal and vegetable ori- gin, was used as background for the determination of the intraluminal heme and nonheme iron pools. Intraluminal Heme and Nonheme Iron Pools In 1972 three groups of researchers published separately the results of iron absorption studies from either wheat or maize biologically labeled with radioiron. The dough was mixed with a soluble iron salt to yield a ferric chloride la- beled with other radioiron and then baked and adminis- tered to subjects. These studies demonstrated that iron salt and food iron were absorbed to the same extent and that the ratio of mean iron absorption between the two absorption rates was close to one. 8–10 These data provided the background for the concept of the intraluminal nonheme iron pool. In the same way, hemoglobin from rabbit and veal muscle tagged with different radioiron and given sepa- rately in one meal demonstrated that hemoglobin absorp- tion is less than 50% of the iron absorption from muscle; its absorption was similar to the absorption from meat in the form of a hamburger when they were mixed together in one meal. 9,10 The concepts of nonheme and heme iron pools were confirmed when veal muscle, maize, rice, and black beans were administered in a meal to 20 individuals (Table 1). 9 Ferritin and hemosiderin from animal foods can be considered a subgroup of the nonheme iron pool. Iron absorption is lower with these than with vegetable foods