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 .
Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial.
OBJECTIVES The objective of the present study was to examine the cross-sectional relation between serum 25-hydroxyvitamin D [ 25-(OH ) D ] levels and  depression in overweight and obese subjects and to assess the effect of vitamin D supplementation on depressive symptoms . DESIGN Cross-sectional study and r and omized double blind controlled trial of 20,000 or 40,000 IU vitamin D per week versus placebo for 1 year . SETTING A total of 441 subjects ( body mass index 28 - 47 kg m(-2 ) , 159 men and 282 women , aged 21 - 70 years ) recruited by advertisements or from the out-patient clinic at the University Hospital of North Norway . MAIN OUTCOME MEASURES Beck Depression Inventory ( BDI ) score with subscales 1 - 13 and 14 - 21 . RESULTS Subjects with serum 25(OH)D levels < 40 nmol L(-1 ) scored significantly higher ( more depressive traits ) than those with serum 25(OH)D levels > or = 40 nmol L(-1 ) on the BDI total [ 6.0 ( 0 - 23 ) versus 4.5 ( 0 - 28 ) ( median and range ) ] and the BDI subscale 1 - 13 [ 2.0 ( 0 - 15 ) versus 1.0 ( 0 - 29.5 ) ] ( P < 0.05 ) . In the two groups given vitamin D , but not in the placebo group , there was a significant improvement in BDI scores after 1 year . There was a significant decrease in serum parathyroid hormone in the two vitamin D groups without a concomitant increase in serum calcium . CONCLUSIONS It appears to be a relation between serum levels of 25(OH)D and symptoms of depression . Supplementation with high doses of vitamin D seems to ameliorate these symptoms indicating a possible causal relationship
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 .