Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron

Background: Dietary iron absorption from a meal is determined by iron statu s, heme- and nonheme-iron contents, and amounts of various dietary factors that influence iron absorption. Limited information is available about the net effect of these factors. Objective: The objective was to develop an algorithm for predicting the eff ects of factors known to influence heme- and nonheme-iron absorption from m eals and diets. Design: The basis for the algorithm was the absorption of iron from a wheat roll (22.1 +/- 0.18%) containing no known inhibitors or enhancers of iron absorption and adjusted to a reference dose absorption of 40%. This basal a bsorption was multiplied by the expected effect of different amounts of die tary factors known to influence iron absorption: phytate, polyphenols, asco rbic acid, meat, fish and seafood, calcium, egg, soy protein, and alcohol. For each factor, an equation describing the dose-effect relation was develo ped. Special considerations were made for interactions between individual f actors. Results: Good agreement was seen when measurements of iron absorption from 24 complete meals were compared with results from use of the algorithm (r(2 ) = 0.987) and when mean iron absorption in 31 subjects served a varied who le diet labeled with heme- and nonheme-iron tracers over a period of 5 d wa s com pared with the mean total iron absorption calculated by using the alg orithm (P = 0.958). Conclusions: This algorithm has several applications. It can be used to pre dict iron absorption from various diets, to estimate the effects expected b y dietary modification, and to translate physiologic into dietary iron requ irements from different types of diets.