Low concentrations of vitamin D have been associated with increased mortality in observational studies in humans, but a cause-and-effect link has been difficult to pin down. This new research published in the British Medical Journal has used a novel approach in which the genetic variants in DHCR7 and CYP2R1 have been measured along with health and mortality statistics in large Danish populations. The genetic variants are linked to a marker of vitamin D status (25-hydroxyvitamin D). Those with genetically low 25-hydroxyvitamin D levels had increased mortality (including cancer but not cardiovascular mortality). This work has used a neat methodology and it may have revealed a causal role for low vitamin D levels in mortality. However, it may require decades for this health risk to become evident and it does not mean that vitamin D supplementation later in life will mitigate the risk.
