Zinc Absorption from Representative Diet in a Chinese Elderly Population Using Stable Isotope Technique.

OBJECTIVE: To determine the dietary zinc absorption in a Chinese elderly population and provide the basic data for the setting of zinc (Zn) recommended nutrient intakes (RNI) for Chinese elderly people. METHODS: A total of 24 elderly people were recruited for this study and were administered oral doses of 3 mg 67Zn and 1.2 mg dysprosium on the fourth day. The primary macronutrients, energy, and phytic acid in the representative diet were examined based on the Chinese National Standard Methods. Fecal samples were collected during the experimental period and analyzed for zinc content, 67Zn isotope ratio, and dysprosium content. RESULTS: The mean (± SD) zinc intake from the representative Chinese diet was 10.6 ± 1.5 mg/d. The phytic acid-to-zinc molar ratio in the diet was 6.4. The absorption rate of 67Zn was 27.9% ± 9.2%. The RNI of zinc, which were calculated by the absorption rate in elderly men and women, were 10.4 and 9.2 mg/d, respectively. CONCLUSION: This study got the dietary Zn absorption in a Chinese elderly population. We found that Zn absorption was higher in elderly men than in elderly women. The current RNI in elderly female is lower than our finding, which indicates that more attention is needed regarding elderly females' zinc status and health.

Estimation of Iron Physiological Requirement in Chinese Children using Single Stable Isotope Tracer Technique.

Objective: This study is to obtain precise data on iron physiological requirements in Chinese children using single stable isotope tracer technique. Methods: Thirty boys (10.6 ± 0.2 years) and 27 girls (10.4 ± 0.2 years) were received oral 6 mg 57Fe each day for 5 consecutive days. Venous blood samples were subsequently drawn to examine the change of total iron concentration and 57Fe abundance at day 0, 14, 28, 60, 90, 180, 360, 450, 540, 630, 720. The iron physiological requirement was calculated by iron loss combined with iron circulation rate once 57Fe abundance stabilized in human body. Results: The iron physiological requirement was significantly lower in boys than those values in girls (16.88 ± 7.12 vs. 18.40 ± 8.81 µg/kg per day, P < 0.05). Correspondingly, the values were calculated as 722.46 ± 8.43 µg/day for boys and 708.40 ± 7.55 µg/day for girls, respectively. Considering nearly 10% iron absorption rate, the estimated average iron physiological requirement was 6.0 mg/day in boys and 6.2 mg/day in girls. Conclusion: This study indicate that iron physiological requirement could require more daily iron intake in girls as compare with the values in boys having the same body weight. These findings would be facilitate to the new revised dietary reference intakes.

Evaluation of Erythrocyte Iron Incorporation in Beijing Prepubertal Children Using a Single Stable Isotope Tracer Method.

OBJECTIVE: To analyze the rate of erythrocyte iron incorporation and provided guidance for the iron nutrition for prepubertal children. METHODS: Fifty-seven prepubertal children of Beijing were involved in this study and each subject was orally administered 3 mg of 57Fe twice daily to obtain a total of 30 mg 57Fe after a 5-d period. The stable isotope ratios in RBCs were determined in 14th day, 28th day, 60th day, and 90th day. The erythrocyte incorporation rate in children was calculated using the stable isotope ratios, blood volume and body iron mass. RESULTS: The percentage of erythrocyte 57Fe incorporation increased starting 14 th day, reached a peak at 60 d (boys: 19.67% ± 0.56%, girls: 21.33% ± 0.59%) and then decreased. The erythrocyte incorporation rates of 57Fe obtained for girls in 60th day was significantly higher than those obtained for boys ( P < 0.0001). CONCLUSIONS: The oral administration of 57Fe to children can be used to obtain erythrocyte iron incorporation within 90 d. Prepubertal girls should begin to increase the intake of iron and further studies should pay more attention to the iron status in prepubertal children.