Effect of cow milk factor(s) on the bioavailability of non-milk riboflavin in rats

Abstract

The influence of milk factor(s) on the bioavailability of non-milk riboflavin was assessed using riboflavin-deficient young rats. Milk retentate prepared by 28 h dialysis of raw cows' milk (3·5% fat) was used as the source of milk factor(s). The repletion test diets provided contained (A) pure riboflavin (300 μg), (B) undialysed raw milk (300 μg), (C) milk retentate alone (75 μg bound riboflavin) or (D) milk retentate (75 μg) plus pure riboflavin (225 μg), as the source of riboflavin, for 15 days. Total hepatic riboflavin content and erythrocyte glutathione reductase (EGR) activity were selected as response criteria. Groups B and D, which received undialysed milk and milk retentate supplemented with pure riboflavin, respectively, had significantly (P < 0·05) greater total hepatic riboflavin content and EGR activity restoration than A. The estimate of the influence of milk factor(s) on the availability of non-milk riboflavin from other dietary sources after correcting for baseline data on total hepatic riboflavin content and EGR activity restoration, showed that bioavilability of non-milk riboflavin was enhanced in the presence of milk factor(s).