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 .
Overview of the Cohort Consortium Vitamin D Pooling Project of Rarer Cancers
The Cohort Consortium Vitamin D Pooling Project of Rarer Cancers ( VDPP ) brought together 10 cohorts to conduct a prospect i ve study of the association between vitamin D status , measured as serum concentrations of 25-hydroxyvitamin D ( 25(OH)D ) , and the development of 7 rarer cancer sites : endometrial , esophageal , gastric , kidney , non-Hodgkin lymphoma , ovarian , and pancreatic cancers . The cohorts come from 3 continents , with participants from a wide range of latitude who are racially diverse . Across each cancer site , there was no evidence of a protective association between higher concentrations of 25-hydroxyvitamin D ( > 75 nmol/L ) and cancer outcome . An increased risk at very high levels ( ≥100 nmol/L ) was noted for pancreatic cancer , confirming previous reports . The articles included in this issue detail the overall design and governance of the project , correlates of vitamin D status , and results from the cancer site-specific investigations . The Vitamin D Pooling Project realizes a major goal of consortium efforts , namely , to rigorously test hypotheses for rarer cancer outcomes that may not be adequately addressed in any one prospect i ve cohort study . The results of this study have application for the planning and conduct of intervention trials , especially in determining potential risks
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 .