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 .
Optimal vitamin D status: a critical analysis on the basis of evidence-based medicine.
CONTEXT Public health authorities around the world recommend widely variable supplementation strategies for adults , whereas several professional organizations , including The Endocrine Society , recommend higher supplementation . METHODS We analyzed published r and omized controlled clinical trials to define the optimal intake or vitamin D status for bone and extraskeletal health . CONCLUSIONS The extraskeletal effects of vitamin D are plausible as based on pre clinical data and observational studies . However , apart from the beneficial effects of 800 IU/d of vitamin D3 for reduction of falls in the elderly , causality remains yet unproven in r and omized controlled trials ( RCTs ) . The greatest risk for cancer , infections , cardiovascular and metabolic diseases is associated with 25-hydroxyvitamin D ( 25OHD ) levels below 20 ng/mL. There is ample evidence from RCTs that calcium and bone homeostasis , estimated from serum 1,25-dihydroxyvitamin D and PTH , calcium absorption , or bone mass , can be normalized by 25OHD levels above 20 ng/mL. Moreover , vitamin D supplementation ( 800 IU/d ) in combination with calcium can reduce fracture incidence by about 20 % . Such a dose will bring serum levels of 25OHD above 20 ng/mL in nearly all postmenopausal women . Based on calculations of the metabolic clearance of 25OHD , a daily intake of 500 - 700 IU of vitamin D3 is sufficient to maintain serum 25OHD levels of 20 ng/mL. Therefore , the recommendations for a daily intake of 1500 - 2000 IU/d or serum 25OHD levels of 30 ng or higher for all adults or elderly subjects , as suggested by The Endocrine Society Task Force , are premature . Fortunately , ongoing RCTs will help to guide us to solve this important public health question
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 .