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 .
A prospective nested case-control study of vitamin D status and pancreatic cancer risk in male smokers.
Sun exposure is associated with lower death rates for pancreatic cancer in some ecological studies . Skin exposure to UVB light induces cutaneous production of precursors to 25-hydroxyvitamin D [ 25(OH)D ] . Pancreatic islet and duct cells express 25(OH)D(3)-1alpha-hydroxylase that generates the biologically active 1,25(OH)(2 ) vitamin D form . Thus , 25(OH)D concentrations could affect pancreatic function and possibly pancreatic cancer etiology . We conducted a prospect i ve nested case-control study in the Alpha-Tocopherol , Beta-Carotene Cancer Prevention cohort of male Finnish smokers , ages 50 to 69 years at baseline , to test whether more adequate vitamin D status , as determined by prediagnostic serum 25(OH)D concentrations , was associated with lower pancreatic cancer risk . Two hundred incident exocrine pancreatic cancer cases that occurred between 1985 and 2001 ( up to 16.7 years of follow-up ) were matched by age and date of blood draw to 400 controls who were alive and free of cancer at the time the case was diagnosed .  Odds ratios ( OR ) and 95 % confidence intervals ( 95 % CI ) were calculated using conditional logistic regression . Higher vitamin D concentrations were associated with a 3-fold increased risk for pancreatic cancer ( highest versus lowest quintile , > 65.5 versus < 32.0 nmol/L : OR , 2.92 ; 95 % CI , 1.56 - 5.48 , P(trend ) = 0.001 ) that remained after excluding cases diagnosed early during follow-up . Contrary to expectations , subjects with higher prediagnostic vitamin D status had an increased pancreatic cancer risk compared with those with lower status . Our findings need to be replicated in other population s and caution is warranted in their interpretation and implication . Our results are intriguing and may provide clues that further the underst and ing of the etiology of this highly fatal cancer
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 .