Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements .
The effects observed for vitamin D3 supplementation remained unchanged when grouped by various characteristics .
However , for vitamin D2 supplementation , increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods .
Conclusions Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease , cancer , and other causes .
Objective To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with  mortality from cardiovascular , cancer , or other conditions  , under various circumstances .
Vitamin D status in patients with stage IV colorectal cancer: findings from Intergroup trial N9741.
PURPOSE Previous studies have suggested that higher plasma 25-hydroxyvitamin D(3 ) [ 25(OH)D ] levels are associated with decreased colorectal cancer risk and improved survival , but the prevalence of vitamin D deficiency in advanced colorectal cancer and its influence on outcomes are unknown . PATIENTS AND METHODS We prospect ively measured plasma 25(OH)D levels in 515 patients with stage IV colorectal cancer participating in a r and omized trial of chemotherapy . Vitamin D deficiency was defined as 25(OH)D lower than 20 ng/mL , insufficiency as 20 to 29 ng/mL , and sufficiency as ≥ 30 ng/mL. We examined the association between baseline 25(OH)D level and selected patient characteristics . Cox proportional hazards models were used to calculate hazard ratios ( HR ) for death , disease progression , and tumor response , adjusted for prognostic factors . RESULTS Among 515 eligible patients , 50 % of the study population was vitamin D deficient , and 82 % were vitamin D insufficient . Plasma 25(OH)D levels were lower in black patients compared to white patients and patients of other race ( median , 10.7 v 21.1 v 19.3 ng/mL , respectively ; P < .001 ) , and females compared to males ( median , 18.3 v 21.7 ng/mL , respectively ; P = .0005 ) . Baseline plasma 25(OH)D levels were not associated with patient outcome , although given the distribution of plasma levels in this cohort , statistical power for survival analyses were limited . CONCLUSION Vitamin D deficiency is highly prevalent among patients with stage IV colorectal cancer receiving first-line chemotherapy , particularly in black and female patients
Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements .
The effects observed for vitamin D3 supplementation remained unchanged when grouped by various characteristics .
However , for vitamin D2 supplementation , increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods .
Conclusions Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease , cancer , and other causes .
Objective To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with  mortality from cardiovascular , cancer , or other conditions  , under various circumstances .