Levels of calcium, magnesium and zinc in urine among adult women in relation to age with special reference to menopause.
OBJECTIVE
This study was initiated to examine, on a basis of large-scale epidemiology, if urinary calcium (Ca), magnesium (Mg) and zinc (Zn) levels change as a function of age and menopause.


METHODS
Spot urine samples were collected from adult women, and analyzed for the minerals. Additional information e.g. on smoking habits was obtained by questionnaires, so that cases were classified into 10,464 never-smokers, 1,351 current smokers and 343 past smokers. The mineral concentrations were evaluated as observed (e.g. Ca-U(ob)), and after correction for creatinine (CR) concentration (e.g. Ca-U(cr)) or specific gravity (SG) (e.g. Ca-U(sg)).


RESULTS
Analyses with never-smokers showed that age-dependent changes in Ca-U(ob), Mg-U(ob) and Zn-U(ob) were minute. Menopause induced a small increase in Ca-U(ob) and a small decrease in Zn-U(ob). Values after CR or SG correction were increased in accordance with both age and menopause, possibly due to age- and menopause-associated decreases in urine density.


CONCLUSIONS
Ca-U(ob), Mg-U(ob) and Zn-U(ob) did not vary substantially throughout life. Ca-U(ob) and Zn-U(ob) were slightly higher and lower, respectively, in post-menopausal women than in pre-menopausal women, but such changes were too small to affect life-long stabilities. Thus, the urinalyses did not suggest need of additional supply of Ca, Mg or Zn at advanced ages. Correction for CR or SG may induce a bias in evaluation of age-dependent changes in mineral concentrations, because CR and SG decrease in accordance with age.
Ikeda
M
M
Kyoto Industrial Health Association, 67 Nishinokyo-Kitatsuboicho, Nakagyo-ku, Kyoto 604-8472, Japan. ikeda@kyotokojohokenkai.or.jp
Ezaki
T
T
Moriguchi
J
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000652:urine*; D002118:Calcium / Q000652:urine*; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D007564:Japan; D008274:Magnesium / Q000652:urine*; D008593:Menopause / Q000652:urine*; D008875:Middle Aged; D009751:Nutritional Requirements; D012907:Smoking / Q000652:urine; D013046:Specific Gravity; D015032:Zinc / Q000652:urine*
D003404:Creatinine; D008274:Magnesium; D015032:Zinc; D002118:Calcium