Research Article

Calcium absorption in postmenopausal Chinese women: a randomized crossover intervention study

Yu-ming Chena1a2, Birgit Teuchera3, Xin-yi Tanga4, Jack R. Daintya3, Kenneth K. C. Leea5, Jean L. F. Wooa6 and Suzanne C. Hoa1 c1

a1 Department of Community & Family Medicine, and the School of Public Health, The Chinese University of Hong Kong, Hong Kong, SAR Peoples Republic of China

a2 Department of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, 510080, Peoples Republic of China

a3 Institute of Food Research, Norwich Research Park, Norwich, NR4 7UA, UK

a4 Department of Pediatrics, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, Peoples Republic of China

a5 School of Pharmacy, The Chinese University of Hong Kong, Hong Kong, SAR Peoples Republic of China

a6 Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, SAR Peoples Republic of China

Abstract

The Ca intake and food sources of Chinese postmenopausal women are quite different from those of their Western counterparts. But, little information on Ca metabolism is available in Chinese populations. We determined true fractional calcium absorption (TFCA), true Ca absorption ( = TFCA × Ca intake, Va), urinary Ca excretion (Vu) and the difference between Va and Vu (Va − u), in response to three dietary Ca intake levels. Twenty-one healthy postmenopausal Chinese women aged 49–64 years were recruited for this randomized crossover trial from a general community, Guangzhou, China. Subjects were randomly assigned to receive 0, 500 and 1000 mg Ca/d for 5 weeks separated by 2-week washout periods. TFCA using Ca stable isotopes, total urinary Ca excretion and Ca intake were determined after 4 weeks of adaptation. Mean values for total Ca intake (Vi) of the three phases were 391 (sd 197), 880 (sd 130) and 1382 (sd 160) mg/d. On usual diet, TFCA, Vu, Va and Va − u were 0·57 (sd 0·12), 175 (sd 59) mg/d, 216 (sd 98) mg/d and 41 (sd 99) mg/d, respectively. With the supplementations of 500 and 1000 mg Ca/d, TFCA significantly decreased to 0·52 (sd 0·12) and 0·43 (sd 0·13) (P < 0·001); whereas urinary Ca (P = 0·003), Va and Va − u increased significantly (P < 0·001). Using a mixed-effects nonlinear regression model, it was estimated that Va − u was approaching a plateau when mean Ca intake reached 1300 mg/d. In conclusion, the present findings suggest postmenopausal Chinese women have high Ca absorption efficiency and a mean Ca intake of about 1300 mg/d is required to maximize the Va − u.

(Received January 10 2006)

(Revised July 17 2006)

(Accepted July 17 2006)

Correspondence:

c1 *Corresponding author: Professor Suzanne C. Ho, Department of Community and Family Medicine, The Chinese University of Hong Kong, 4th Floor, School of Public Health, Prince of Wales Hospital, Shatin, N.T., Hong Kong SAR, fax +852 2602 6986, email suzanneho@cuhk.edu.hk

Footnotes

Abbreviations: NTx, cross-linked N-telopeptide; PTH, parathyroid hormone; TFCA, true fractional calcium absorption

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