EFFECTS OF NITROGEN, PHOSPHORUS, AND CAFFEINE ON CALCIUM BALANCE IN WOMEN

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 99  (1) , 46-55
Abstract
Women during the postmenopausal years lose bone at a rate of 10-15% per decade. This loss is a principal factor in the development of postmenopausal osteoporosis. An inadequate Ca intake may be a contributory factor in this postmenopausal bone loss. The effects of different levels of N, P and caffeine intake on Ca balance and on certain of its components were assessed in 170 studies in normal middle-aged, but still premenopausal women. Statistically significant negative associations with Ca balance were found for N and for caffeine, but no effect could be found for P. Higher N intakes were associated with proportionately higher levels of urinary Ca; higher P intake was associated with slightly lower levels of urinary Ca but also with slightly more intestinal secretion of Ca. Since these 2 effects were opposite in direction, there was no net association of different P intakes with Ca balance. Caffeine intake was associated with higher levels of both urinary Ca and intestinal Ca secretion. None of the 3 intake variables was associated with differences in Ca absorption efficiency. Both the N and the caffeine effects were proportional to intake. The magnitude of the effects observed was such that a 50% increase in intake of N above the group mean intake value would be predicted to result in Ca balance shift of -0.032 g/day. For caffeine, the corresponding Ca balance shift would be predicted to be -0.006 g/day.