Bioavailability of Iron-fortified Whey Protein Concentrate in Iron-deficient Rats

An iron-fortified whey protein concentrate (Fe-WPC) was prepared by addition of ferric chloride to concentrated whey. A large part of the iron in the Fe-WPC existed as complexes with proteins such as ${\beta}$-lactoglobulin. The bioavailability of iron from Fe-WPC was evaluated using iron-deficient rats, in comparison with heme iron. Rats were separated into a control group and an iron-deficiency group. Rats in the control group were given the standard diet containing ferrous sulfate as the source of iron throughout the experimental feeding period. Rats in the iron-deficiency group were made anemic by feeding on an Fe-deficient diet without any added iron for 3 wk. After the iron-deficiency period, the iron-deficiency group was separated into an Fe-WPC group and a heme iron group fed Fe-WPC and hemin as the sole source of iron, respectively. The hemoglobin content, iron content in liver, hemoglobin regeneration efficiency (HRE) and apparent iron absorption rate were examined when iron-deficient rats were fed either Fe-WPC or hemin as the sole source of iron for 20 d. Hemoglobin content was significantly higher in the rats fed the Fe-WPC diet than in rats fed the hemin diet. HRE in rats fed the Fe-WPC diet was significantly higher than in rats fed the hemin diet. The apparent iron absorption rate in rats fed the Fe-WPC diet tended to be higher than in rats fed the hemin diet (p = 0.054). The solubility of iron in the small intestine of rats at 2.5 h after ingestion of the Fe-WPC diet was approximately twice that of rats fed the hemin diet. These results indicated that the iron bioavailability of Fe-WPC was higher than that of hemin, which seemed due, in part, to the different iron solubility in the intestine.