Genetically low vitamin D concentrations cause premature death
A new Danish study indicates that gene variations, which are associated with low levels of vitamin D in the blood, can lead to premature death. It is not yet known whether dietary supplements can counteract this effect.
The amount of vitamin D in your blood depends on what you eat and how much sunlight you get. Now a study shows, that it is also depends on your genetic make-up.
Individuals, who are born with gene variants that are associated with low levels of vitamin D in the blood, face an increased risk of premature death.
"For the first time we can confirm that low levels of vitamin D actually is a cause of a greater propensity to premature death," says Shoaib Afzal from Herlev Hospital.
Afzal is the lead author of the new study, recently published in the British Medical Journal.
Genes control vitamin D level
In the study, scientists have taken a close look at two genes, which influence how much vitamin D, we have in our blood.
The gene CYP2R1 controls how we convert vitamin D in the liver, while the gene DHCR7 controls how much vitamin D we can receive from the sun.
Professor Lars Rejnmark of the Department of Medical Endocrinology at Aarhus University Hospital, explains that all genes are found in active or less active variants. If, for instance, you have the active version of one of the genes seen in the study, you will form more vitamin D while in the sun.
“The study also shows that you will probably live longer if you have this very active version of the gene," says Rejnmark.
Blood from 30.000 Danes
First the scientists measured the level of vitamin D in the blood of 30,000 Danes. As many previous studies have shown, they quickly detected the statistical correlation between low levels of vitamin D and early death.
Taking the study one step further, they analysed the genetical variations in the blood. Using their experience from the analysis, they went even further. This time analysing the genetics of 96,000 Danes.
The analysis showed that variations in the genes can make vitamin D levels drop by two nano-molar vitamin D per litre of blood. “In contrast to other studies in this field, we have proven a causal relationship between mortality and the level of vitamin D by looking at genetical variations,” says Afzal.
Effect of dietary supplements on mortality rates stay unknown
Currently, the scientists do not know whether taking dietary supplements containing vitamin D has any effect on the mortality rates.
“Honestly, we don’t know yet," says Professor Rejnmark.
The authors of the study also approach this problem.
"Our study shows that low levels of vitamin D causes increased mortality, but the best way to increase levels of the vitamin in the population on a large scale, has not yet been clarified,” says Professor Børge Nordestgaard from Herlev Hospital in a press release.
The study has its limitations
The British Medical Journal writes about the study:
“The study is well conducted but is subject to potential limitations, as are all mendelian randomisation studies”, and points out; “we should be careful not to over-interpret”.
They draw attention to the fact that the same Danish scientists recently found a correlation between concentrations of vitamin D and the risk of developing type 2 diabetes - a study which was also based on the data from the Herlev-Østerbro Study.
“The epidemiological cliché that ‘more data are required to confirm this finding’ once again applies,” the report concludes.
Translated by: Hugh Matthews
- 'Genetically low vitamin D concentrations and increased mortality: mendelian randomisation analysis in three large cohorts' 2014, British Medical Journal, doi: http://dx.doi.org/10.1136/bmj.g6330
- Vitamin D genes and mortality