In subgroup analyses , all cause mortality was significantly lower in trials with vitamin D3 supplementation than in trials with vitamin D2 supplementation ( P for interaction=0.04 ) ; neither vitamin D3 nor vitamin D2 was associated with a statistically significant reduction in all cause mortality .
CONCLUSIONS Vitamin D supplementation alone was not associated with  all cause mortality in adults compared with placebo or no treatment .
Vitamin D supplementation reduced the risk of cancer death by 16 % .
Additional large clinical studies are needed to determine whether vitamin D3 supplementation is associated with lower all cause mortality .
OBJECTIVE To investigate whether vitamin D supplementation is associated with lower mortality in adults .
Vitamin D, Insulin Secretion, Sensitivity, and Lipids
OBJECTIVE Vitamin D deficiency is associated with an unfavorable metabolic profile in observational studies . The intention was to compare insulin sensitivity ( the primary end point ) and secretion and lipids in subjects with low and high serum 25(OH)D ( 25-hydroxyvitamin D ) levels and to assess the effect of vitamin D supplementation on the same outcomes among the participants with low serum 25(OH)D levels . RESEARCH DESIGN AND METHODS Participants were recruited from a population -based study ( the Tromsø Study ) based on their serum 25(OH)D measurements . A 3-h hyperglycemic clamp was performed , and the participants with low serum 25(OH)D levels were thereafter r and omized to receive capsules of 20,000 IU vitamin D3 or identical-looking placebo twice weekly for 6 months . A final hyperglycemic clamp was then performed . RESULTS The 52 participants with high serum 25(OH)D levels ( 85.6 ± 13.5 nmol/L [ mean ± SD ] ) had significantly higher insulin sensitivity index ( ISI ) and lower HbA1c and triglycerides ( TGs ) than the 108 participants with low serum 25(OH)D ( 40.3 ± 12.8 nmol/L ) , but the differences in ISI and TGs were not significant after adjustments . After supplementation , serum 25(OH)D was 142.7 ± 25.7 and 42.9 ± 17.3 nmol/L in 49 of 51 completing participants r and omized to vitamin D and 45 of 53 r and omized to placebo , respectively . At the end of the study , there were no statistically significant differences in the outcome variables between the two groups . CONCLUSIONS Vitamin D supplementation to apparently healthy subjects with insufficient serum 25(OH)D levels does not improve insulin sensitivity or secretion or serum lipid profile
In subgroup analyses , all cause mortality was significantly lower in trials with vitamin D3 supplementation than in trials with vitamin D2 supplementation ( P for interaction=0.04 ) ; neither vitamin D3 nor vitamin D2 was associated with a statistically significant reduction in all cause mortality .
CONCLUSIONS Vitamin D supplementation alone was not associated with  all cause mortality in adults compared with placebo or no treatment .
Vitamin D supplementation reduced the risk of cancer death by 16 % .
Additional large clinical studies are needed to determine whether vitamin D3 supplementation is associated with lower all cause mortality .
OBJECTIVE To investigate whether vitamin D supplementation is associated with lower mortality in adults .