Comparison of a Modified Hemoglobin Regeneration Efficiency Method with a Slope-Ratio Assay in Measuring Relative Bioavailability of Cocoa Powder Iron Using Rats

Abstract

The slope-ratio assay is being used as a gold standard for determining iron bioavailability in foods. We compared the modified hemoglobin (Hb) regeneration efficiency (HRE) method (Yokoi K, Konomi A, & Otagi M (2009) Br J Nutr 102: 215-220) with the slope-ratio assay for measurement of iron bioavailability. The relative bioavailability of iron in cocoa powder was measured by both methods using ferric citrate as a control (i.e., 1.00). In the slope-ratio assay, thirty-two 4-week-old male F/344N rats were depleted in iron stores for 28days, and then eight groups of four rats each were repleted for 25days using graded levels of dietary ferric citrate or the cocoa powder. The slope for the cocoa powder 1.720g Hb/L/(mg Fe/kg) was 0.99 that of ferric citrate 1.727g Hb/L/(mg Fe/kg). On the other hand, the HRE value of the cocoa powder was 0.96 that of ferric citrate, based on the previous report. The relative iron bioavailabilities measured by both methods agreed, indicating that the modified HRE method is compatible with the slope-ratio assay in measuring the bioavailability of iron in foods.