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 .
[GRADE guidelines: 5. Rating the quality of evidence: publication bias].
In the GRADE approach , r and omized trials are classified as high quality evidence and observational studies as low quality evidence but both can be rated down if a body of evidence is associated with a high risk of publication bias . Even when individual studies included in best- evidence summaries have a low risk of bias , publication bias can result in substantial overestimates of effect . Authors should suspect publication bias when available evidence comes from a number of small studies most of which have been commercially funded . A number of approaches based on examination of the pattern of data are available to help assess publication bias . The most popular of these is the funnel plot ; all , however , have substantial limitations . Publication bias is likely frequent , and caution in the face of early results , particularly with small sample size and number of events , is warranted
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 .