There is currently no firm evidence that vitamin D supplementation decreases or increases cancer occurrence in predominantly elderly community-dwelling women .
Vitamin D₃ supplementation  decreased cancer mortality  and vitamin D supplementation  decreased all-cause mortality , but these estimates are at risk of type I errors due to the fact that too few participants were examined , and to risks of attrition bias originating from substantial dropout of participants .
Combined vitamin D₃ and calcium supplements  increased nephrolithiasis , whereas it remains unclear from the included trials whether vitamin D₃ , calcium , or both were responsible for this effect .
BACKGROUND The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory .
OBJECTIVES To assess the beneficial and harmful effects of vitamin D supplementation for prevention of cancer in adults .
Prospective study of serum 25(OH)-vitamin D concentration and risk of oesophageal and gastric cancers
We prospect ively examined the relation between pretrial serum vitamin D status and risk of oesophageal and gastric cancers among subjects who developed cancer over 5.25 years of follow-up , including 545 oesophageal squamous cell carcinomas ( ESCC ) , 353 gastric cardia adenocarcinomas , 81 gastric noncardia adenocarcinomas , and an age- and sex-stratified r and om sample of 1105 subjects . The distribution of  serum 25(OH)D  was calculated using the known sampling weights . For the cohort as a whole , the 25th , 50th , and 75th percentile concentrations of 25(OH)-vitamin D were 19.6 , 31.9 , and 48.7 nmol l−1 , respectively , and we found that higher serum 25(OH)D concentrations were associated with monotonically increasing risk of ESCC in men , but not in women . Comparing men in the fourth quartile of serum 25(OH)D concentrations to those in the first , we found a hazard ratio ( HR ) ( 95 % confidence interval ( CI ) ) of 1.77 ( 1.16–2.70 ) , P trend=0.0033 . The same comparison in women had a HR ( 95 % CI ) of 1.06 ( 0.71–1.59 ) , P trend=0.70 . We found no associations for gastric cardia or noncardia adenocarcinoma . Among subjects with low vitamin D status , higher serum 25(OH)D concentrations were associated with significantly increased risk of ESCC in men , but not in women . Further refinements of the analysis did not suggest any factors , which could explain this unexpected result
There is currently no firm evidence that vitamin D supplementation decreases or increases cancer occurrence in predominantly elderly community-dwelling women .
Vitamin D₃ supplementation  decreased cancer mortality  and vitamin D supplementation  decreased all-cause mortality , but these estimates are at risk of type I errors due to the fact that too few participants were examined , and to risks of attrition bias originating from substantial dropout of participants .
Combined vitamin D₃ and calcium supplements  increased nephrolithiasis , whereas it remains unclear from the included trials whether vitamin D₃ , calcium , or both were responsible for this effect .
BACKGROUND The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory .
OBJECTIVES To assess the beneficial and harmful effects of vitamin D supplementation for prevention of cancer in adults .