There is currently no firm evidence that vitamin D supplementation decreases or increases cancer occurrence in predominantly elderly community-dwelling women .
Vitamin D₃ supplementation  decreased cancer mortality  and vitamin D supplementation  decreased all-cause mortality , but these estimates are at risk of type I errors due to the fact that too few participants were examined , and to risks of attrition bias originating from substantial dropout of participants .
Combined vitamin D₃ and calcium supplements  increased nephrolithiasis , whereas it remains unclear from the included trials whether vitamin D₃ , calcium , or both were responsible for this effect .
BACKGROUND The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory .
OBJECTIVES To assess the beneficial and harmful effects of vitamin D supplementation for prevention of cancer in adults .
Biochemical bone markers and bone mineral density during postmenopausal hormone replacement therapy with and without vitamin D3: a prospective, controlled, randomized study.
The effects of  postmenopausal hormone replacement therapy ( HRT ) and vitamin D on the serum concentrations of three bone biochemical markers and their associations with bone mineral density ( BMD ) were studied in a population -based 1-yr follow-up study . A total of 72 healthy postmenopausal women were r and omized into 4 treatment groups : HRT group ( sequential combination of 2 mg estradiol valerate and 1 mg cyproterone acetate ) , D group ( vitamin D3 , 300 IU/day ) , HRT+D group ( both of the above ) , and placebo group ( calcium lactate , 500 mg/day ) . Serum concentrations of osteocalcin ( OC ) and bone-specific alkaline phosphatase ( BAP ) were measured as biochemical markers of bone formation , and serum type I collagen carboxy-terminal telopeptide was measured as a marker of bone resorption at baseline and after 6 and 12 months of treatment . To investigate the associations of these markers with BMD , lumbar ( L2-L4 ) and femoral neck BMDs were determined by dual x-ray absorptiometry at baseline and after 2.5 yr of treatment . In both hormone groups , the serum concentrations of the three bone metabolic markers had decreased after 12 months . Those of OC decreased by 29.2 % ( P = 0.017 ) in the HRT group and by 37.3 % ( P = 0.004 ) in the HRT+D group , and BAP concentrations decreased by 34.4 % ( P < 0.001 ) in the HRT group and by 36.2 % ( P < 0.001 ) in the HRT+D group . Serum type I collagen carboxy-terminal telopeptide concentrations had decreased by 21.6 % ( P = 0.012 ) in HRT group and by 14.1 % ( P = 0.011 ) in the HRT+D group . In the D group , the serum concentrations of BAP had decreased by 11.7 % ( P = 0.040 ) after 12 months , but the other two markers showed no change . The only change seen in the placebo group was a 19.2 % increase in OC concentrations ( P = 0.041 ) after 6 months , but at 12 months , the mean OC level was similar to that at baseline . After 2.5 yr , both lumbar and femoral BMD had decreased in the D group [ 2.1 % ( P = 0.022 ) and 3.6 % ( P = 0.019 ) , respectively ] and in the placebo group [ 3.3 % ( P = 0.009 ) and 2.7 % ( P = 0.010 ) , respectively ] , whereas no significant changes occurred in the hormone groups . There were significant inverse correlations between the changes in lumbar and femoral BMDs and changes in all three biochemical markers ( r = -0.240 through -0.336 ; P = 0.005 - 0.064 ) . Our results suggest that HRT counteracts the biochemical changes caused by increased bone turnover associated with menopause . Importantly , the changes in bone markers correlate with long term changes in BMDs of lumbar spine and femoral neck .  Low dose vitamin D treatment , however , seems to have only marginal effects on bone metabolism in early postmenopausal healthy women
There is currently no firm evidence that vitamin D supplementation decreases or increases cancer occurrence in predominantly elderly community-dwelling women .
Vitamin D₃ supplementation  decreased cancer mortality  and vitamin D supplementation  decreased all-cause mortality , but these estimates are at risk of type I errors due to the fact that too few participants were examined , and to risks of attrition bias originating from substantial dropout of participants .
Combined vitamin D₃ and calcium supplements  increased nephrolithiasis , whereas it remains unclear from the included trials whether vitamin D₃ , calcium , or both were responsible for this effect .
BACKGROUND The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory .
OBJECTIVES To assess the beneficial and harmful effects of vitamin D supplementation for prevention of cancer in adults .