Dietary recommendations and r and omized trials on vitamin D supplementation should evaluate whether increases in circulating 25-hydroxyvitamin D levels match expectations -- for instance , the average increases obtained by trials on vitamin D3 without concomitant calcium supplements
CONTEXT Few studies in subjects over 50 yr of age have evaluated the influence of variable doses of vitamin D supplementation on serum 25-hydroxyvitamin D levels .
OBJECTIVE We performed a meta- analysis of changes in circulating 25-hydroxyvitamin D level associated with vitamin D supplementation in Caucasian subjects over 50 yr old .
Serum ionized calcium, intact PTH and novel markers of bone turnover in bedridden elderly patients.
Chronic immobilization could markedly affect calcium and bone metabolism in elderly people . To investigate this , and to test the theory of ' type II ' osteoporosis in bedridden elderly patients with low vitamin D status , 55 such subjects were examined .  Serum concentrations of ionized calcium ( Ca++ ) , intact parathyrin ( PTH ) and two novel markers of bone collagen formation ( carboxyterminal propeptide of type I procollagen ; PICP ) and resorption ( carboxyterminal crosslinked telopeptide of type I collagen ; ICTP ) were measured . The effects on these parameters after 40 weeks of supplementation with vitamin D ( 1000 IU d-1 ) and /or calcium ( 1 g d-1 ) were subsequently prospect ively evaluated . Despite low ( mean 11.6 nmoll-1 ) serum 25-hydroxyvitamin D levels ( 25-OHD ) , those of 1,25-dihydroxy-vitamin D ( 1,25-(OH)2D ) were mostly normal . Neither correlated with Ca++ or PTH . PTH correlated negatively not only with Ca++ ( r = -0.328 , P < 0.05 ) but also with ICTP ( r = -0.306 , P < 0.05 ) . Mean PICP was normal but ICTP was elevated and tended to correlate positively with Ca++ ( r = 0.268 , P = 0.06 ) . Vitamin D supplementation did not change PICP or ICTP considerably , despite slightly increased 1,25-(OH)2D and slightly decreased PTH . Ca++ values were normal and remained stable . In conclusion , Ca++ and PTH are poor indicators of vitamin D status in chronically immobilized elderly subjects . Furthermore , the results suggest that the increased bone resorption is not due to ' type II ' secondary hyperparathyroidism ; rather the resorption is primarily increased . Correction of vitamin D deficiency does not seem to benefit ageing bones unless adequate mechanical loading is provided
Dietary recommendations and r and omized trials on vitamin D supplementation should evaluate whether increases in circulating 25-hydroxyvitamin D levels match expectations -- for instance , the average increases obtained by trials on vitamin D3 without concomitant calcium supplements
CONTEXT Few studies in subjects over 50 yr of age have evaluated the influence of variable doses of vitamin D supplementation on serum 25-hydroxyvitamin D levels .
OBJECTIVE We performed a meta- analysis of changes in circulating 25-hydroxyvitamin D level associated with vitamin D supplementation in Caucasian subjects over 50 yr old .