British Journal of Nutrition

Studies of mineral absorption and bioavaility

True fractional calcium absorption in Chinese children measured with stable isotopes (42Ca and 44Ca)

Warren T.L. Leea1, Sophie S.F. Leunga1, Susan J.Fairweather-Taita2, Dora M.Y. Leunga1, Heidi S.Y. Tsanga1, John Eaglesa2, Tom Foxa2, S.H. Wanga3, Y.C. Xua3, W.P. Zenga4, Joseph Laua5 and J.R.L. Masareia6

a1 Department of Paediatrics, Faculty of Medicine, The Chinese University of Hongkong, Shatin, Hongkong

a2 AFRC Institute of Food Research Norwich Laboratory, Norwich Research Park, Colney, Norwich NR4 7UA

a3 Department of Nutrition and Food Hygiene, Sun Yat Sen University of Medical Sciences, Guangzhou, China

a4 Jiangmen Epidemic Station, Jiangmen, Guandong Province, China

a5 Centre for Clinical Trials and Epidemiological Research, Faculty of Medicine, The Chinese University of Hongkong, Shatin, Hongkong

a6 Department of Chemical Pathology, Faculty of Medicine, The Chinese University of Hongkong, Shatin, Hongkong

Abstract

True fractional Ca absorption (TFCA) was compared in children with different habitual Ca intakes using a double-label stable-isotope technique. Chinese children aged 7 years from Hongkong (n 22) and Jiangmen (n 12) participated in the study. An oral administration of 8 mg 44Ca in 100 g chocolate milk was given shortly after an intravenous injection of 0·75 mg 42Ca. Ca isotopic ratios were determined in urine samples collected 24 h later using thermal-ionization mass spectrometry. There was no significant difference in TFCA between Jiangmen and Hongkong children (P=0·16). TFCA of a lower-Ca-intake group (Ca > 500 mg/d, n 19) with mean Ca intake 359 mg/d was 63·1 (SD 10·7)%; and that of a higher-Ca-intake group (Ca > 500 mg/d, n 15) with mean Ca intake 862 mg/d was 54·8 (SD 7·3)%; the difference in TFCA was significant (P=0·016). Serum levels of 25-hydroxycholecalciferol of the children were adequate (33·7 (SD 7·7) ng/ml). The present study indicates that growing children accustomed to a low-Ca diet appear to be able to enhance their absorptive capacity. If it is assumed that dietary Ca absorption by Chinese children resembles their TFCA from a single meal of chocolate milk, then the recommended dietary allowance (RDA) for Ca for Chinese children would be lower than the US RDA (800 mg/d), which is based on an estimated 40% Ca absorption as reported for Caucasian children. A comparative absorption study is necessary to determine whether there is any difference in TFCA between Caucasian and Chinese children.

(Received September 13 1993)

(Revised April 12 1994)

(Accepted April 26 1994)

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