Genetically low vitamin D levels are associated with increased mortality, a Danish study published in the BMJ has found.
The study observed 95,766 white participants of Danish descent from three cohorts in Copenhagen, who had genetic variants that affected vitamin D levels. Other factors known to affect mortality, such as smoking, alcohol consumption, physical activity, blood pressure, cholesterol levels and body mass index were also recorded. Between study entry and 2013, 10,349 participants from the three cohorts died.
The study was conducted to discern whether taking vitamin supplements would increase life expectancy.
The study found that those with genetically low vitamin D levels were two per cent more likely to experience all cause mortality, and three per cent more likely to for cancer mortality. However, it also observed that low levels of vitamin D did not affect cardiovascular mortality rates. It is also unknown whether low levels of vitamin D are a cause of increased mortality, or merely a marker of poor health, which leads to early death.
The authors concluded that 'the clinical implication of our findings remain limited, as widespread vitamin D supplementation can be recommended only after benefit is shown in randomised intervention trials.'
Several trials on the effects of vitamin D supplementation will begin reporting their results in 2017.
Writing in an editorial on the study, Paul Welsh, a fellow at the British Heart Foundation and Naveed Sattar, professor of metabolic medicine at the University of Glasgow, said: 'Even if we believe the study to be robust, and despite the narrow confidence intervals around the estimates, the borderline significance of the findings means that we should be careful not to over-interpret.' Professor Sattar summarised his position: 'In short, this study gives hope that trials may show something positive but we need to wait for trials to change anything.'