Lean beef and beef fat interact to enhance nonheme iron absorption in rats

Nonheme iron absorption is enhanced when meat replaces non-meat protein sources in a meal. Our objective was to examine the hypothesis that both lean and fat fractions of meat contribute to this enhancement. Weanling rats were assigned, according to a 3 x 3 factorial design, to one of nine nutritionally complete diets formulated to contain various combinations of protein (lean beef, skim milk or egg white) and fat sources (beef fat, milk fat or partially hydrogenated vegetable fat). Diets contained 20% protein and 20% fat. After 4 d of consuming the assigned diets, the rats were deprived of food overnight and offered a meal of their respective diet labeled extrinsically with 59FeCl3. Feeding of the unlabeled diets was continued for 14 d. Iron absorption was estimated from 59Fe retention, monitored by whole-body counting over the 14-d period. Absorption was highest from diets containing beef regardless of the fat source, but the combination of beef and beef fat was highest of all. In the comparison of absorption from the lean beef and other diets, there was significant interaction between lean beef and fat source on iron absorption. These results suggest that the iron absorption-enhancing properties of meat may involve an interaction between the lean and fat fractions of meat.