IRON AND ZINC INTERACTIONS IN HUMANS

Iron deficiency is the most common nutritional deficiency in the world ; zinc deficiency is associated with poor growth and development and i mpaired immune response. Several Third World countries are taking meas ures to increase the dietary intake of iron and zinc with fortificatio n of foods or dietary supplements. Several studies showed that high ir on concentrations can negatively affect zinc absorption in adults when these trace minerals are given in solution. However, when iron and zi nc are given in a meal, this effect is not observed. Solomons (J Nutr 1986;116:927-35) postulated that the total amount of ionic species aff ects the absorption of zinc and that a total dose of >25 mg Fe may pro duce a measurable effect on zinc absorption. This could occur if iron supplements are taken with a meal, and iron experts recommend that iro n supplements be taken between meals. Recent studies using stable isot opes showed that fortifying foods with iron at current fortification a mounts has no adverse effect on zinc absorption. There are 5 zinc salt s listed as generally recommended as safe (GRAS) by the US Food and Dr ug Administration for food fortification. From 1970 to 1987, the total amount of zinc salts used in food continually increased, with zinc ox ide and zinc sulfate showing the largest increases. Twelve iron source s are listed as GRAS; elemental iron has become the source of choice b ecause it is less expensive to produce and has fewer organoleptic prob lems. Use of ferrous fumarate is also increasing.