Current methods for estimating dietary iron bioavailability do not work in China

Three current equations for estimating iron bioavailability were evaluated, and adjustments were proposed that would allow us to most effectively study iron bioavailability in China. Dietary intake data were obtained from 24-h dietary recalls taken over three consecutive days as part of the third Chinese National Nutrition Survey. Hemoglobin status was measured for 42,606 Chinese adults aged 18-60 y. The mean iron intake was 24.4 mg per capita per day, which was 177% of the Chinese RDA (209% of U.S. RDA). About 18% of the sample was classified as being anemic, indicating a large iron deficiency anemia and iron bioavailability problem in China. A number of methods proposed by World Health Organization and U.S. scholars were examined for adjusting iron bioavailability. Even the methods that consider several iron enhancers and inhibitors did not work adequately for the Chinese diet. The statistical assessment of the fit between iron bioavailability and hemoglobin status provided direction for adjusting the best of these predictive equations. We propose a new predictive approach for iron bioavailability which is more predictive of Chinese iron status. Consideration of additional dietary elements such as rice and bean consumption patterns are important. Our findings provide insight into additional factors which may influence iron bioavailability as well as possible improved methods for estimating the combined effect of multiple dietary factors on iron bioavailability, particularly in a vegetarian diet.