A new study published online first, and in an upcoming Lancet, shows that genetic factors affect the risk of a person having vitamin D insufficiency. The article is written by Prof Tim Spector, King’s College, London, UK; Dr Elina Hyppönen, UCL Institute of Child Health, London, UK; Dr Thomas J Wang, Massachusetts General Hospital, Boston, USA, and international colleagues from the SUNLIGHT consortium.
Vitamin D is crucial for maintenance of musculoskeletal health, and might also have a role in extraskeletal tissues. Determinants of circulating vitamin D concentrations include sun exposure and diet, but previous work showing clustering of low vitamin D concentrations within families and twins suggests that genetic factors also play a part. In this study, the authors aimed to identify common genetic variants affecting vitamin D concentrations and risk of insufficiency.
The authors did a genome-wide association study of almost 34,000 white people of European descent from 15 studies. A range of conventional techniques, including radioimmunoassay and mass spectrometry, were used to determine serum vitamin D concentrations. Vitamin D insufficiency was defined as concentrations lower than 75 nmol/L or 50 nmol/L.
Variants at three genetic sites or ‘loci’ were significantly associated with vitamin D concentrations. These loci were near genes involved in cholesterol synthesis, vitamin D metabolism, and vitamin D transport. Participants with a genotype score (combining the three confirmed variants) in the highest quartile (the 25% at greatest risk) were at two-and-a-half times increased risk of having vitamin D concentrations lower than 75 nmol compared with those in the lowest quartile (The 25% at lowest risk).
The authors conclude: “Our findings establish a role for common genetic variants in regulation of circulating vitamin D concentrations. The presence of harmful alleles at the three confirmed loci more than doubled the risk of vitamin D insufficiency. These findings improve our understanding of vitamin D regulation and could assist identification of a subgroup of the white population who are most at risk of vitamin D insufficiency and who may need extra levels of supplementation.*”
They add: “We studied only white individuals of European descent. Whether the genetic variants we identified affect vitamin D status in other racial or ethnic groups is unknown and warrants further study.”
In an accompanying comment, Dr Roger Bouillon, Katholieke Universiteit Leuven, Belgium, says: “Today’s results only partly explain the wide variability of vitamin D status, and whether these genetically based variations modify the health outcomes in vitamin D deficiency is not known. Therefore, the battle against vitamin D deficiency will probably not be modified by these new findings. We need additional studies to explain the mechanisms underlying the pandemic of vitamin D deficiency and, above all, we need a strategy to correct this serious worldwide deficiency.”
For full Article and Comment see: http://press.thelancet.com/vitamind.pdf