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 .
The tolerability and biochemical effects of high‐dose bolus vitamin D2 and D3 supplementation in patients with vitamin D insufficiency
Objectives : To investigate the practicality and tolerability of high‐dose intramuscular ( i.m . ) vitamin D2 or oral vitamin D3 replacement in vitamin D‐insufficient patients , and to evaluate the biochemical efficacy of each formulation . Methods : Sixty‐nine patients with vitamin D insufficiency [ 25‐hydroxyvitamin D ( 25(OH)D ) < 40 nmol/L ] were recruited from the Rheumatology Outpatient Department of St George 's Hospital , London . In study 1 , 50 patients received 300 000 IU i.m . vitamin D2 ( ergocalciferol ) . In study 2 , 19 patients received 300 000 IU oral vitamin D3 ( cholecalciferol ) under observation . Biochemical response was measured at baseline , and at 12 and 24 weeks . Results : Bolus i.m . vitamin D2 or oral vitamin D3 was well tolerated . The change from baseline in serum 25(OH)D was significantly greater at 6 and 12 weeks in study 2 ( p<0.0001 and < 0.0001 , respectively ) . In study 1 , a modest increase in mean serum 25(OH)D at 6 , 12 , and 24 weeks was observed but no patients achieved a serum 25(OH)D concentration ⩾50 nmol/L. PTH remained elevated in 42 % of patients with secondary hyperparathyroidism at 12 weeks . In study 2 , 100 % and 89 % of patients had serum 25(OH)D>50 nmol/L at 6 and 12 weeks , respectively . All patients with elevated baseline PTH were fully suppressed at 12 weeks . No cases of hypercalcaemia were observed in either group . Conclusion : The 300 000‐IU bolus of vitamin D2 or D3 was practical , well tolerated , and safe . Vitamin D3 had greater potency than equimolar vitamin D2 , with a higher , sustained serum 25(OH)D response and efficacious PTH suppression . To adequately treat vitamin D insufficiency we would recommend administering 300 000 IU oral vitamin D3 approximately three times per year
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 .