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 .
Effect of Vitamin D Supplementation on Blood Pressure in Blacks
Blacks have significantly higher rates of hypertension than whites , and lower circulating levels of 25-hydroxyvitamin D. There are few data about the effect of vitamin D3 ( cholecalciferol ) supplementation on  blood pressure in blacks . During 2 winters from 2008 to 2010 , 283 blacks ( median age , 51 years ) were r and omized into a 4-arm , double-blind trial for 3 months of placebo , 1000 , 2000 , or 4000 international units of cholecalciferol per day . At baseline , 3 months , and 6 months , systolic and diastolic pressure and 25-hydroxyvitamin D were measured . The 3-month follow-up was completed in 250 ( 88 % ) participants . The difference in systolic pressure between baseline and 3 months was + 1.7 mm Hg for those receiving placebo , −0.66 mm Hg for 1000 U/d , −3.4 mm Hg for 2000 U/d , and −4.0 mm Hg for 4000 U/d of cholecalciferol ( −1.4 mm Hg for each additional 1000 U/d of cholecalciferol ; P=0.04 ) . For each 1-ng/mL increase in plasma 25-hydroxyvitamin D , there was a significant 0.2-mm Hg reduction in systolic pressure ( P=0.02 ) . There was no effect of cholecalciferol supplementation on diastolic pressure ( P=0.37 ) . Within an unselected population of blacks , 3 months of oral vitamin D3 supplementation significantly , yet modestly , lowered systolic pressure . Future trials of vitamin D supplementation  on blood pressure are needed to confirm these promising results , particularly among blacks , a population for whom vitamin D deficiency may play a more specific mechanistic role in the pathogenesis of hypertension
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 .