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 .
Vitamin D Status and Impact of Vitamin D3 and/or Calcium Supplementation in a Randomized Pilot Study in the Southeastern United States
Objective : Vitamin D supplementation may be required for certain subgroups in the United States in whom status and intake are inadequate , but the impact of various doses , and whether calcium administration jointly or independently influences vitamin D metabolite levels , is unclear . Methods : In a pilot chemoprevention trial of biomarkers of risk for colorectal adenoma , we measured the impact of vitamin D supplementation and /or calcium supplementation on plasma vitamin D metabolite concentrations . Ninety-two adult men and women living in the southeastern United States were r and omized to 800 IU vitamin D3 , 2000 mg elemental calcium , both , or placebo daily for 6 months . We examined vitamin D status at baseline and postintervention and compared the change in plasma 25-hydroxyvitamin D ( 25(OH)D ) and 1,25(OH)2D levels by intervention group using general linear models . Results : Eighty-two percent of the study population had insufficient plasma 25(OH)D concentrations ( < 75 nmol/L ) at baseline , with the lowest levels observed among African American participants . Vitamin D supplements , with or without calcium supplementation , raised plasma 25(OH)D concentrations , on average , by 25 to 26 nmol/L. Half of the study participants were classified as having sufficient 25(OH)D status after 6 months of 800 IU of vitamin D3 daily . Calcium alone did not influence 25(OH)D concentrations . Conclusion : In this southeastern U.S. population , half of the study participants receiving 800 IU vitamin D3 daily had blood 25(OH)D concentrations of ≤75 nmol/L after a 6-month intervention period , supporting higher vitamin D dose requirements estimated by some groups . More research is needed to identify the optimal vitamin D dose to improve 25(OH)D status in various at-risk population
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 .