Recent meta-analyses reinforce the finding that 10 - 20 μg per day of vitamin D can reduce all-cause mortality and cancer mortality in middle-aged and older people .
Although vitamin D doses were greater than those assessed in the past , we found no new evidence that supplementation could have an effect on most non-skeletal conditions , including cardiovascular disease , adiposity , glucose metabolism , mood disorders , muscular function , tuberculosis , and colorectal adenomas , or on maternal and perinatal conditions .
The compilation of results from 83 trials showed that vitamin D supplementation had no significant effect on biomarkers of systemic inflammation .
The main new finding highlighted by this systematic review is that vitamin D supplementation might help to prevent common upper respiratory tract infections and asthma exacerbations .
There remains little evidence to suggest that vitamin D supplementation has an effect on most conditions , including chronic inflammation , despite use of increased doses of vitamin D , strengthening the hypothesis that low vitamin D status is a consequence of ill health , rather than its cause .
We further hypothesise that vitamin D supplementation could exert immunomodulatory effects that strengthen resistance to acute infections , which would reduce the risk of death in debilitated individuals .
Effect of Vitamin D and Calcium Supplementation on Cancer Incidence in Older Women: A Randomized Clinical Trial
Importance Evidence suggests that low vitamin D status may increase the risk of cancer . Objective To determine if dietary supplementation with vitamin D3 and calcium reduces the risk of  cancer among older women . Design , Setting , and Participants A 4-year , double-blind , placebo-controlled , population -based r and omized clinical trial in 31 rural counties ( June 24 , 2009 , to August 26 , 2015—the final date of follow-up ) . A total of 2303 healthy postmenopausal women 55 years or older were r and omized , 1156 to the treatment group and 1147 to the placebo group . Duration of treatment was 4 years . Interventions The treatment group ( vitamin D3 + calcium group ) received 2000 IU/d of vitamin D3 and 1500 mg/d of calcium ; the placebo group received identical placebos . Main Outcomes and Measures The primary outcome was the incidence of all-type cancer ( excluding nonmelanoma skin cancers ) , which was evaluated using Kaplan-Meier survival analysis and proportional hazards modeling . Results Among 2303 r and omized women ( mean age , 65.2 years [ SD , 7.0 ] ; mean baseline serum 25-hydroxyvitamin D level , 32.8 ng/mL [ SD , 10.5 ] ) , 2064 ( 90 % ) completed the study . At year 1 , serum 25-hydroxyvitamin D levels were 43.9 ng/mL in the vitamin D3 + calcium group and 31.6 ng/mL in the placebo group . A new diagnosis of cancer was confirmed in 109 participants , 45 ( 3.89 % ) in the vitamin D3 + calcium group and 64 ( 5.58 % ) in the placebo group ( difference , 1.69 % [ 95 % CI , −0.06 % to 3.46 % ] ; P = .06 ) . Kaplan-Meier incidence over 4 years was 0.042 ( 95 % CI , 0.032 to 0.056 ) in the vitamin D3 + calcium group and 0.060 ( 95 % CI , 0.048 to 0.076 ) in the placebo group ; P = .06 . In unadjusted Cox proportional hazards regression , the hazard ratio was 0.70 ( 95 % CI , 0.47 to 1.02 ) . Adverse events potentially related to the study included renal calculi ( 16 participants in the vitamin D3 + calcium group and 10 in the placebo group ) , and elevated serum calcium levels ( 6 in the vitamin D3 + calcium group and 2 in the placebo group ) . Conclusions and Relevance Among healthy postmenopausal older women with a mean baseline serum 25-hydroxyvitamin D level of 32.8 ng/mL , supplementation with vitamin D3 and calcium compared with placebo did not result in a significantly lower risk of all-type cancer at 4 years . Further research is necessary to assess the possible role of vitamin D in cancer prevention . Trial Registration clinical trials.gov Identifier :
Recent meta-analyses reinforce the finding that 10 - 20 μg per day of vitamin D can reduce all-cause mortality and cancer mortality in middle-aged and older people .
Although vitamin D doses were greater than those assessed in the past , we found no new evidence that supplementation could have an effect on most non-skeletal conditions , including cardiovascular disease , adiposity , glucose metabolism , mood disorders , muscular function , tuberculosis , and colorectal adenomas , or on maternal and perinatal conditions .
The compilation of results from 83 trials showed that vitamin D supplementation had no significant effect on biomarkers of systemic inflammation .
The main new finding highlighted by this systematic review is that vitamin D supplementation might help to prevent common upper respiratory tract infections and asthma exacerbations .
There remains little evidence to suggest that vitamin D supplementation has an effect on most conditions , including chronic inflammation , despite use of increased doses of vitamin D , strengthening the hypothesis that low vitamin D status is a consequence of ill health , rather than its cause .
We further hypothesise that vitamin D supplementation could exert immunomodulatory effects that strengthen resistance to acute infections , which would reduce the risk of death in debilitated individuals .