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 .
Calcium plus vitamin D supplementation and the risk of nonmelanoma and melanoma skin cancer: post hoc analyses of the women's health initiative randomized controlled trial.
PURPOSE In light of inverse relationships reported in observational studies of vitamin D intake and serum 25-hydroxyvitamin D levels with risk of nonmelanoma skin cancer ( NMSC ) and melanoma , we evaluated the effects of vitamin D combined with calcium supplementation on skin cancer in a r and omized placebo-controlled trial . METHODS Postmenopausal women age 50 to 79 years ( N = 36,282 ) enrolled onto the Women 's Health Initiative ( WHI ) calcium/vitamin D clinical trial were r and omly assigned to receive 1,000 mg of elemental calcium plus 400 IU of vitamin D3 ( CaD ) daily or placebo for a mean follow-up period of 7.0 years . NMSC and melanoma skin cancers were ascertained by annual self-report ; melanoma skin cancers underwent physician adjudication . RESULTS Neither incident NMSC nor melanoma rates differed between treatment ( hazard ratio [ HR ] , 1.02 ; 95 % CI , 0.95 to 1.07 ) and placebo groups ( HR , 0.86 ; 95 % CI , 0.64 to 1.16 ) . In subgroup analyses , women with history of NMSC assigned to CaD had a reduced risk of melanoma versus those receiving placebo ( HR , 0.43 ; 95 % CI , 0.21 to 0.90 ; P(interaction ) = .038 ) , which was not observed in women without history of NMSC . CONCLUSION Vitamin D supplementation at a relatively low dose plus calcium did not reduce the overall incidence of NMSC or melanoma . However , in women with history of NMSC , CaD supplementation reduced melanoma risk , suggesting a potential role for calcium and vitamin D supplements in this high-risk group . Results from this post hoc subgroup analysis should be interpreted with caution but warrant additional investigation
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 .