Conclusions and Relevance In this systematic review and meta- analysis , neither intermittent nor daily dosing with st and ard doses of vitamin D alone was associated with reduced risk of fracture , but daily supplementation with both vitamin D and calcium was a more promising strategy
Importance Vitamin D and calcium supplements are recommended for the prevention of fracture , but previous r and omized clinical trials ( RCTs ) have reported conflicting results , with uncertainty about optimal doses and regimens for supplementation and their overall effectiveness .
Objective To assess the risks of fracture associated with differences in concentrations of 25-hydroxyvitamin D ( 25[OH]D ) in observational studies and the risks of fracture associated with supplementation with vitamin D alone or in combination with calcium in RCTs .
A Trial of Calcium and Vitamin D for the Prevention of Colorectal Adenomas.
BACKGROUND Epidemiologic and pre clinical data suggest that higher intake and serum levels of vitamin D and higher intake of calcium reduce the risk of colorectal neoplasia . To further study the chemopreventive potential of these nutrients , we conducted a r and omized , double-blind , placebo-controlled trial of supplementation with vitamin D , calcium , or both for the prevention of colorectal adenomas . METHODS We recruited patients with recently diagnosed adenomas and no known colorectal polyps remaining after complete colonoscopy . We r and omly assigned 2259 participants to receive daily vitamin D3 ( 1000 IU ) , calcium as carbonate ( 1200 mg ) , both , or neither in a partial 2 × 2 factorial design . Women could elect to receive calcium plus r and om assignment to vitamin D or placebo . Follow-up colonoscopy was anticipated to be performed 3 or 5 years after the baseline examinations , according to the endoscopist 's recommendation . The primary end point was adenomas diagnosed in the interval from r and omization through the anticipated surveillance colonoscopy . RESULTS Participants who were r and omly assigned to receive vitamin D had a mean net increase in serum 25-hydroxyvitamin D levels of 7.83 ng per milliliter , relative to participants given placebo . Overall , 43 % of participants had one or more adenomas diagnosed during follow-up . The adjusted risk ratios for recurrent adenomas were 0.99 ( 95 % confidence interval [ CI ] , 0.89 to 1.09 ) with vitamin D versus no vitamin D , 0.95 ( 95 % CI , 0.85 to 1.06 ) with calcium versus no calcium , and 0.93 ( 95 % CI , 0.80 to 1.08 ) with both agents versus neither agent . The findings for advanced adenomas were similar . There were few serious adverse events . CONCLUSIONS Daily supplementation with vitamin D3 ( 1000 IU ) , calcium ( 1200 mg ) , or both after removal of colorectal adenomas did not significantly reduce the risk of recurrent colorectal adenomas over a period of 3 to 5 years . ( Funded by the National Cancer Institute ; Clinical Trials.gov number , NCT00153816 . )
Conclusions and Relevance In this systematic review and meta- analysis , neither intermittent nor daily dosing with st and ard doses of vitamin D alone was associated with reduced risk of fracture , but daily supplementation with both vitamin D and calcium was a more promising strategy
Importance Vitamin D and calcium supplements are recommended for the prevention of fracture , but previous r and omized clinical trials ( RCTs ) have reported conflicting results , with uncertainty about optimal doses and regimens for supplementation and their overall effectiveness .
Objective To assess the risks of fracture associated with differences in concentrations of 25-hydroxyvitamin D ( 25[OH]D ) in observational studies and the risks of fracture associated with supplementation with vitamin D alone or in combination with calcium in RCTs .