title: Sodium is the leading dietary factor associated with urinary calcium excretion in Hong Kong Chinese adults.
abstract: We conducted a cross-sectional population-based study comprising 1010 Hong Kong Chinese (500 men and 510 women) aged 25-74 years during 1995-6. The study examined the important dietary, lifestyle and anthropometric factors associated with urinary calcium excretion. Dietary intakes were assessed by means of food frequency questionnaire. Spot urine was collected to measure the urinary excretion profiles of calcium (Ca), sodium (Na), potassium (K) and creatinine (Cr). When expressed as ratios of cations to urinary Cr, significant relationships were noted between urinary Ca and Na (r: approximately 0.6), and between urinary Ca and K (r: 0.17-0.21). Stepwise multiple linear regression analyses were carried out separately in men and women aged below and above 50 years. We found that urinary Na/Cr was the leading independent factor associated with urinary Ca/Cr in all four age and sex groups. It accounted for 22% of urinary Ca/Cr variations in women aged below 50 years, and 35-43% in the other three age and sex groups. We estimated that urinary Ca excretion increased by about 1.4 (range 1.37-1.43) mmol per 100 mmol increase in urinary Na. Except in men aged 50 years and over, urinary K/Cr was inversely associated with urinary Ca/Cr in all groups. Age was independently and positively associated with urinary Ca/ Cr in subjects aged below 50 years. We did not observe any significant relation between urinary Ca/Cr and dietary protein, phosphorus, alcohol drinking and smoking. In conclusion, we found that urinary Na/Cr, but not dietary protein, Ca or phosphorus, is the most important factor influencing urinary Ca/Cr excretion in our population. Urinary K is a potential factor for Ca conservation.
authors.affiliation: Department of Community and Family Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, NT. Suzanneho@cuhk.edu.hk
authors.forename: S C
authors.initials: SC
authors.lastname: Ho
authors.forename: Y M
authors.initials: YM
authors.lastname: Chen
authors.forename: J L
authors.initials: JL
authors.lastname: Woo
authors.forename: S S
authors.initials: SS
authors.lastname: Leung
authors.forename: T H
authors.initials: TH
authors.lastname: Lam
authors.forename: E D
authors.initials: ED
authors.lastname: Janus
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002118:Calcium / Q000652:urine*; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D004032:Diet / Q000009:adverse effects*; D005260:Female; D006723:Hong Kong / Q000208:ethnology; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000652:urine*; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*
chemical_list: D017673:Sodium Chloride, Dietary; D003404:Creatinine; D011188:Potassium; D002118:Calcium