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 and breast cancer recurrence in the Women's Healthy Eating and Living (WHEL) Study.
BACKGROUND There is a paucity of research evaluating the relation between  vitamin D  and recurrence of breast cancer after treatment . OBJECTIVE This study was design ed to evaluate the associations between circulating concentrations of  25-hydroxyvitamin D [ 25(OH)D ]  and dietary , supplemental , and total intake of vitamin D  and recurrent or new breast cancer events within the Women 's Healthy Eating and Living ( WHEL ) Study . DESIGN A prospect i ve cohort study design ( n = 3085 ) was used to evaluate the relation between dietary , supplemental , and total vitamin D intake and recurrent breast cancer , and a nested case-control study with 512 matched pairs was used for analysis of the association between 25(OH)D and breast cancer recurrence . RESULTS No relation between 25(OH)D and breast cancer recurrence was observed . Compared with women with serum concentrations of 25(OH)D ≥ 30 ng/mL , adjusted odds ratios ( 95 % CI ) for breast cancer recurrence were 1.14 ( 0.57 , 2.31 ) for those with concentrations < 10 ng/mL , 1.00 ( 0.68 - 1.48 ) for concentrations ≥ 10 and < 20 ng/mL , and 1.05 ( 0.76 , 1.47 ) for concentrations ≥ 20 and < 30 ng/mL. No significant associations were observed when analyses were stratified by pre- and postmenopausal status or for local , regional , or distant recurrence or death . Vitamin D intake was not related to breast cancer recurrence overall , although for premenopausal women there was a significant inverse association between dietary vitamin D intake and recurrence ( P for trend = 0.02 ) . CONCLUSION These results do not provide support for a relation between concentrations of 25(OH)D after treatment and the recurrence of breast cancer . This trial is registered at clinical trials.gov for the WHEL Study as NCT00003787
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 .