The vast majority of studies reported inverse associations between 25(OH)D concentration and all-cause mortality .
This association appeared to be non-linear , with progressively lower mortality with increasing 25(OH)D up to a point , beyond which there was no further decrease .
There is moderate evidence that vitamin D status is inversely associated with cancer mortality and death due to respiratory diseases , while for cardiovascular mortality , there is weak evidence of an association in observational studies , which is not supported by the data from intervention or Mendelian r and omization studies .
Epidemiological evidence suggests that vitamin D deficiency is associated with increased mortality , but it is unclear whether this is explained by reverse causation , and if there are specific causes of death for which vitamin D might be important .
The inverse association between serum 25-hydroxyvitamin D and mortality may be modified by vitamin A status and use of vitamin A supplements
Background Low serum 25-hydroxyvitamin D [ 25(OH)D ] levels have been associated with higher risk of many diseases that affect mortality , including cardiovascular disease ( CVD ) and cancer . The inverse association between serum 25(OH)D and mortality may be modified by excess circulating vitamin A , due to interactions of vitamin A at the level of the vitamin D nuclear receptor . In this prospect i ve cohort study , we investigated whether the association of 25(OH)D with all-cause , cancer , and CVD mortality  was modified by circulating vitamin A or preformed vitamin A intake from supplements . Methods We analyzed 15,998 adults in the Third National Health and Nutrition Examination Survey ( NHANES III ) , 1988–1994 . Mortality data for all-cause ( n = 3890 ) , cancer ( n = 844 ) , and CVD mortality ( n = 1715 ) were assessed through December 2006 .  Serum 25(OH)D was measured using a radioimmunoassay kit , vitamin A biomarkers were measured by HPLC , and information on supplement use was obtained by self-report . Multivariable hazard ratios ( HRs ) and corresponding 95 % confidence intervals ( CI ) were estimated by proportional hazards regression . Results Serum 25(OH)D was significantly inversely associated with all-cause mortality ( HR 0.93 , 95 % CI 0.89 , 0.97 , per 10 ng/mL increase ) and also with CVD mortality and mortality due to non-cancer/non-cardiovascular causes , but not with cancer mortality . The observed inverse associations remained statistically significant only among participants with serum retinyl esters < 7.0 μg/dL. High intake ( > 5000 IU/day ) of preformed vitamin A from supplements attenuated the inverse association of 25(OH)D with overall mortality . The observed interactions were not statistically significant . Conclusions 25(OH)D was inversely associated with overall mortality , CVD mortality , and mortality due to non-cancer/non-CVD causes , but not with cancer mortality . A possible interaction between vitamin A exposure and 25(OH)D concentration appears to be associated with an attenuation of the inverse association between risk of death and quartile of 25(OH)D concentration
The vast majority of studies reported inverse associations between 25(OH)D concentration and all-cause mortality .
This association appeared to be non-linear , with progressively lower mortality with increasing 25(OH)D up to a point , beyond which there was no further decrease .
There is moderate evidence that vitamin D status is inversely associated with cancer mortality and death due to respiratory diseases , while for cardiovascular mortality , there is weak evidence of an association in observational studies , which is not supported by the data from intervention or Mendelian r and omization studies .
Epidemiological evidence suggests that vitamin D deficiency is associated with increased mortality , but it is unclear whether this is explained by reverse causation , and if there are specific causes of death for which vitamin D might be important .