a1 Department of Paediatrics, Faculity of Medicine, The Chinese University of Hongkong, Shatin, Hongkong
a2 Department of Nutrition and Food Hygiene, Sun Yat Sen University of Medical Sciences, Guangzhou, China
a3 Jiangmen Epidemic Station, Jiangmen, Guangdong Province, China
a4 Centre for Clinial Trials and Epidemiologial Research, Faculty of Medicine, The Chinese University of Hongkong, Shatin, Hongkong
a5 Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich NR4 7UA
A double-blind controlled Ca supplementation trial was conducted for 6 months in thirty-four 7-year-old Chinese children from Hongkong and Jiangmen, China. The children were randomly allocated to the study group (n 17) or control group (n 17), and a CaCO3 tablet (300 mg Ca) or a placebo tablet was taken daily. True fractional Ca absorption (TFCA) was evaluated before and after the trial using stable isotopes: 8 mg44Ca mixed in 100 g chocolate milk was given after an intravenous injection of 0·75 mg 42Ca. There was no significant difference in baseline TFCA between the study group (60·6 (SD 11·4)%) and the controls (58·2 (SD 9.0)% P = 0·55). Serum 25-hydroxycholecalciferol levels were comparable between the two groups (P = 0·71). After 6 months, TFCA of the study group (55·6 (SD 12·7)%) was significantly lower than that of the controls (64·3 (SD 10·7)% P = 0·015). By comparing the individual changes in TFCA after the trial between the two groups there was a non-significant reduction in TFCA (5·03 (SD 12·4)% P = 0·11, Wilcoxon signed-rank test) in the study group (60·6–55·6%), whereas a significant increase in TFCA (6·17(SD 7·7)% P = 0·004, Wilcoxon signed-rank test) was observed in the controls (58·2–64·3%). The differential in TFCA between the two groups after 6 months was significantly different (P = 0·001), and remained significant after adjustment for baseline dietary intakes, weight and height by multiple-regression analysis (P = 0·003). If the mechanism of TFCA from chocolate milk in response to the treatment effects is similar to that from the total diet, then our results suggest that children with adequate vitamin D status can adapt to a change in Ca intake by adjusting the efficiency of TFCA. In corollary, children on habitually-low Ca diets have a higher TFCA than the counterparts with higher Ca diets.
(Received March 01 1994)
(Revised June 01 1994)
(Accepted June 24 1994)
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