title: Studies on zinc bioavailability from a representative diet in Chinese urban women of childbearing age using a double label stable isotope technique.
abstract: The objectives of the study were to determine dietary zinc bioavailability by using a double label stable isotope technique, and to identify the zinc content and levels of some possible factors which may affect zinc utilization in a typical representative Chinese urban diet. Twenty urban women of childbearing age were fed a diet extrinsically labeled with 67Zn and received intravenous (i.v.) injections of 70Zn. Fecal monitoring, urine monitoring and chemical balance technique were used simultaneously for comparisons. Isotopic enrichment in feces and urine after oral and i.v. administration of stable zinc isotopes was measured to determine the ways of zinc absorption. The mean (+/-SD) zinc intake from the representative Chinese diet was 10.22+/-0.80 mg/day, which is lower than the reference nutrient intake (RNI) level (11.5 mg/day), and mainly came from the subsidiary foods (63%). The mean dietary Fe/Zn weight was 1.1+/-0.1. The phytate/zinc molar ratio in the diet was about 3:1. The phytic acidxCa/zinc molar ratio in the diet was about 45:1. The apparent and true absorption rates of 67Zn were 36.2+/-9.7% and 38.2+/-10.1%, respectively, which were higher than the apparent absorption determined by balance technique (29.7+/-10.6%). The mean fractional absorption (FA) determined in urine was 35.7+/-13.3. In conclusion, the subsidiary food is the main source of dietary zinc in this typical diet. The extrinsic labeling technique by use of stable isotopes was more reliable and accurate to determine zinc absorption. Moreover, the double isotopic tracer ratio (DITR) technique applied to urine samples was a more practical and valuable way to evaluate zinc absorption than other methods. It can be speculated that iron and phytic acid might not be the main inhibitors in the representative Chinese diet.
authors.affiliation: Key laboratory of Trace Element Nutrition of The Ministry of Health, Institute of Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, No. 27 Nanwei Road, Xuanwu District, Beijing 100050, China.
authors.forename: Lichen
authors.initials: L
authors.lastname: Yang
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Yang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Piao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.forename: Penggao
authors.initials: P
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
mesh_terms: D000042:Absorption; D000328:Adult; D044466:Asian People; D001682:Biological Availability; D002681:China; D004032:Diet; D019587:Dietary Supplements; D004602:Elements; D005243:Feces; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D009747:Nutritional Physiological Phenomena; D009753:Nutritive Value; D015032:Zinc / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D017967:Zinc Compounds; D015033:Zinc Isotopes; D015037:Zinc Radioisotopes
chemical_list: D004602:Elements; D017967:Zinc Compounds; D015033:Zinc Isotopes; D015037:Zinc Radioisotopes; D015032:Zinc