There was a suggestion that whole-body or lumbar spine BMD may be a useful biomarker in older people but not in adolescents .
This systematic review confirmed that circulating 25(OH)D is a robust and reliable marker of vitamin D status .
BACKGROUND Although serum 25-hydroxyvitamin D [ 25(OH)D ] is the currently accepted vitamin D status marker of choice , use of other biomarkers or functional endpoints have been suggested .
OBJECTIVE The objective was to systematic ally review the effectiveness of 25(OH)D , parathyroid hormone ( PTH ) , bone turnover markers , bone mineral density ( BMD ) , and calcium absorption as biomarkers of vitamin D status .
Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial.
BACKGROUND Numerous observational studies have found supplemental calcium and vitamin D to be associated with reduced risk of common cancers . However , interventional studies to test this effect are lacking . OBJECTIVE The purpose of this analysis was to determine the efficacy of calcium alone and calcium plus vitamin D in reducing incident cancer risk  of all types . DESIGN This was a 4-y , population -based , double-blind , r and omized placebo-controlled trial . The primary outcome was fracture incidence , and the principal secondary outcome was cancer incidence . The subjects were 1179 community-dwelling women r and omly selected from the population of healthy postmenopausal women aged > 55 y in a 9-county rural area of Nebraska centered at latitude 41.4 degrees N. Subjects were r and omly assigned to receive 1400 - 1500 mg supplemental calcium/d alone ( Ca-only ) , supplemental calcium plus 1100 IU vitamin D3/d ( Ca + D ) , or placebo . RESULTS When analyzed by intention to treat , cancer incidence was lower in the Ca + D women than in the placebo control subjects ( P < 0.03 ) . With the use of logistic regression , the unadjusted relative risks ( RR ) of incident cancer in the Ca + D and Ca-only groups were 0.402 ( P = 0.01 ) and 0.532 ( P = 0.06 ) , respectively . When analysis was confined to cancers diagnosed after the first 12 mo , RR for the Ca + D group fell to 0.232 ( CI : 0.09 , 0.60 ; P < 0.005 ) but did not change significantly for the Ca-only group . In multiple logistic regression models , both treatment and serum 25-hydroxyvitamin D concentrations were significant , independent predictors of cancer risk . CONCLUSIONS Improving calcium and vitamin D nutritional status substantially reduces  all-cancer risk in postmenopausal women . This trial was registered at clinical trials.gov as NCT00352170
There was a suggestion that whole-body or lumbar spine BMD may be a useful biomarker in older people but not in adolescents .
This systematic review confirmed that circulating 25(OH)D is a robust and reliable marker of vitamin D status .
BACKGROUND Although serum 25-hydroxyvitamin D [ 25(OH)D ] is the currently accepted vitamin D status marker of choice , use of other biomarkers or functional endpoints have been suggested .
OBJECTIVE The objective was to systematic ally review the effectiveness of 25(OH)D , parathyroid hormone ( PTH ) , bone turnover markers , bone mineral density ( BMD ) , and calcium absorption as biomarkers of vitamin D status .