Effects of stearic acid and beef tallow on iron utilization by the rat

Two experiments were done in which anemic rats were fed diets containing safflower oil or stearic acid and low (10 ppm) or adequate (39-42 ppm) iron. Diets were 24% fat by weight. In the stearic acid diets, 2% (Experiment 1) or 4% (Experiment 2) of the fat was supplied by safflower oil to satisfy essential fatty acid requirements. Repletion of hemoglobin, hematocrit, and liver iron was assessed. Compared with safflower oil in both experiments, stearic acid had a significant positive effect (P less than 0.0001) on repletion of hemoglobin (Hb), hematocrit (Hct), and liver iron concentration; the effect on Hb and Hct was most pronounced when dietary iron was low. When expressed as g Hb/mg Fe intake, Hb repletion was affected by a significant interaction between fat and Fe (P less than 0.002) and was greatest in rats fed low iron stearic acid diets. In a third experiment, rats were fed low dietary iron and 24% safflower oil, 20% stearic acid + 4% safflower oil, 3.2% stearic acid + 20.8% safflower oil, or 20% beef tallow + 4% safflower oil. The 20% beef tallow provided 3.2% stearic acid in the total diet. The response of Hb and Hct were similar to those in the first two experiments for rats fed safflower oil or stearic acid. Rats fed beef tallow had significantly greater (P less than 0.05) Hb and Hct repletion than did rats fed safflower oil, although the degree of repletion was less than that observed in rats fed 20% stearic acid. There was no difference in iron repletion of rats fed 3.2% stearic acid and rats fed beef tallow. We conclude that stearic acid enhances iron utilization by rats.