The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels
Background A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D ( 25OHD ) levels on non-skeletal outcomes .
We performed a systematic quantitative review on characteristics of r and omized clinical trials ( RCTs ) included in meta-analyses ( MAs ) on non-skeletal effects of vitamin D supplementation .
Baseline characteristics of participants in the VITamin D and OmegA-3 TriaL (VITAL).
Evidence for a role of supplemental vitamin D and marine omega-3 fatty acids in preventing cancer and cardiovascular disease ( CVD ) remains inconclusive and insufficient to inform nutritional recommendations for primary prevention . The VITamin D and Omega-A 3 TriaL ( VITAL ) is an ongoing nationwide , r and omized , double-blind , placebo-controlled clinical trial design ed to fill this knowledge gap . The study population consists of 25,874 U.S. adults without cancer or CVD at baseline , who were selected only on age ( men aged ≥50 and women aged ≥55 ) , with an oversampling of African Americans ( n=5,107 ) . In a 2 × 2 factorial design , participants were r and omized to one of four supplement groups : [ 1 ] active vitamin D3 ( cholecalciferol ; 2000 IU/d ) and active marine omega-3 fatty acids ( Omacor ® fish oil , eicosapentaenoic acid [ EPA ] and docosahexaenoic acid [ DHA ] , 1g/d ) ; [ 2 ] active vitamin D and omega-3 placebo ; [ 3 ] vitamin D placebo and active marine omega-3 fatty acids ; or [ 4 ] vitamin D placebo and omega-3 placebo . The mean length of the r and omized treatment period will be 5 years . The r and omization was successful , as evidence d by similar distributions of baseline demographic , health , and behavioral characteristics across treatment groups . The similar distribution of known potential confounders across treatment groups strongly suggests that unmeasured or unknown potential confounders are also equally distributed . VITAL is expected to provide important information on the benefit-risk balance of vitamin D and omega-3 fatty acid supplementation when taken for the primary prevention of cancer and CVD
The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels
Background A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D ( 25OHD ) levels on non-skeletal outcomes .
We performed a systematic quantitative review on characteristics of r and omized clinical trials ( RCTs ) included in meta-analyses ( MAs ) on non-skeletal effects of vitamin D supplementation .