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 .
Serum vitamin D concentration and prostate cancer risk: a nested case-control study.
BACKGROUND Epidemiological studies have yielded inconsistent associations between vitamin D status and prostate cancer risk , and few studies have evaluated whether the associations vary by disease aggressiveness . We investigated the association between  vitamin D status , as determined by serum 25-hydroxyvitamin D [ 25(OH)D ] level , and risk of prostate cancer in a case-control study nested within the Prostate , Lung , Colorectal , and Ovarian ( PLCO ) Cancer Screening Trial . METHODS The study included 749 case patients with incident prostate cancer who were diagnosed 1 - 8 years after blood draw and 781 control subjects who were frequency matched by age at cohort entry , time since initial screening , and calendar year of cohort entry . All study participants were selected from the trial screening arm ( which includes annual st and ardized prostate cancer screening ) . Conditional logistic regression was used to estimate adjusted odds ratios ( ORs ) with 95 % confidence intervals ( CIs ) by quintile of season-st and ardized serum 25(OH)D concentration . Statistical tests were two-sided . RESULTS No statistically significant trend in overall prostate cancer risk was observed with increasing season-st and ardized serum 25(OH)D level . However , serum 25(OH)D concentrations greater than the lowest quintile ( Q1 ) were associated with increased risk of aggressive ( Gleason sum > or = 7 or clinical stage III or IV ) disease ( in a model adjusting for matching factors , study center , and history of diabetes , ORs for Q2 vs Q1 = 1.20 , 95 % CI = 0.80 to 1.81 , for Q3 vs Q1 = 1.96 , 95 % CI = 1.34 to 2.87 , for Q4 vs Q1 = 1.61 , 95 % CI = 1.09 to 2.38 , and for Q5 vs Q1 = 1.37 , 95 % CI = 0.92 to 2.05 ; P(trend ) = .05 ) . The rates of aggressive prostate cancer for increasing quintiles of serum 25(OH)D were 406 , 479 , 780 , 633 , and 544 per 100 000 person-years . In exploratory analyses , these associations with aggressive disease were consistent across subgroups defined by age , family history of prostate cancer , diabetes , body mass index , vigorous physical activity , calcium intake , study center , season of blood collection , and assay batch . CONCLUSION The findings of this large prospect i ve study do not support the hypothesis that vitamin D is associated with decreased risk of prostate cancer ; indeed , higher circulating 25(OH)D concentrations may be associated with increased risk of aggressive disease
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 .