OBJECTIVESIn order to understand the absorption and utilization of calcium, iron and zinc in cow milk, soy milk powder and dephytinized soy milk powder in the children and adolescents, and to lay a foundation for the improvement of protein and mineral nutrition in Chinese residents with popularizing consumption of soy milk powder.

METHODSTotally, 57 boys aged 12 to 14 years were selected and divided into three groups, matched by age, hemoglobin concentration, height and weight. The boys were given 220 ml of fortified and dephytinized soy milk, soy milk or cow milk, respectively, containing calcium 270 mg, iron 4 mg and zinc 4 mg, which were labeled with stable isotopes (44)Ca, (58)Fe and (70)Zn in a single serving size, and their feces were labeled with brilliant blue and dysprosium. Feces specimens were collected for all the subjects and absorption rate of calcium, iron and zinc were measured for all the children who took fortified and dephytinized soy milk, soy milk or cow milk, respectively. Calcium in feces was measured with heat ionized mass spectrometry, and recovery of (58)Fe and (70)Zn in feces and content of dysprosium were measured with induction coupling iso-ionic mass spectrometry, and then absorption rates of iron and zinc were calculated and adjusted by the recovery rate of dysprosium.

RESULTSIron absorption rate was (6.7 +/- 3.8)% in soy milk powder group, (15.5 +/- 9.2)% in the cow milk group and (20.6 +/- 7.3)% in dephytinized soy milk powder group, respectively. Calcium absorption rate was (43.5 +/- 10.7)%, (64.2 +/- 11.4)%, and (50.9 +/- 6.6)% in the three groups, respectively. Absorption rate of zinc was (11.3 +/- 6.5)%, (31.2 +/- 10.4)% and (20.1 +/- 7.4)%, respectively. Significant increase in absorption of calcium, iron and zinc was observed in the groups with fortified and dephytinized soy milk powder, as compared with those consuming nondephytinized soy milk powder. Absorption rate of calcium and zinc was significantly higher in the group with cow milk than that in the group with dephytinized and fortified soy milk powder, and iron bioavailability was lower in the group with cow milk than that with dephytinized soy milk powder, with no significant difference. Absorption rates of calcium, iron and zinc were higher in children of China due to their long term adaptation to dietary intake of lower mineral and protein, and higher fiber.

CONCLUSIONSBioavailability of calcium, iron and zinc in soy milk powder could be increased by dephytinized treatment for it.