Bioavailability of egg yolk iron measured by hemoglobin regeneration in anemic rats

Biological availability of egg yolk iron and effect of egg yolk on absorption of iron from the reference salt, ferrous sulfate, were evaluated in hemoglobin repletion assays with anemic rats. Three measures of response, hemoglobin concentration, gain in hemoglobin iron content, and gain in carcass iron content were related to total dietary iron intake by regression analyses. Relative biological value (RBV) of yolk iron, in diets without ascorbic acid, compared to that of the reference salt was 85%. RBV of egg iron was equivalent to ferrous sulfate iron in diets containing 1 g ascorbic acid per kilogram of diet. Increasing increments of egg yolk in diets containing ascorbic acid had no significant effect on utilization of iron from the reference salt as measured by gain in hemoglobin or carcass iron content during the regeneration period. Stimulation of iron utilization from egg yolk by ascorbic acid was mild in these studies and was less in diets containing 32 mg/kg of egg yolk iron than in those containing 15 mg/kg of iron from egg.