Low levels of vitamin D may play a causal role in the development of hypertension, researchers found.

by Parker Brown
June 26, 2014

Low levels of vitamin D may play a causal role in the development of hypertension, researchers found.

Each 10% increase in vitamin D concentration was associated with lower diastolic blood pressure (-.29 mm Hg, 95% CI minus 0.52-minus 0.07, P=0.01), lower systolic blood pressure (-.37mm Hg, 95% CI minus 0.73-minus 0.003, P=.052), and reduced odds of hypertension (OR .92, 95% CI 0.87-0.97 P=.002), according to Karani Vimaleswaran, PhD, of University College London, and colleagues.

In a Mendelian randomization study, the authors analyzed variants of genes that affect vitamin D synthesis and substrate availability in up to 146,581 participants from D-CarDia — a large collaboration of studies — and from other studies. Their analysis appeared online June 26 in The Lancet Diabetes & Endocrinology.

Previous research has found a similar association between low levels of vitamin D and hypertension. But Vimaleswaran and colleagues were interested in circumventing both reverse causation and confounding variables.

The meta-analysis included 31 cohort studies of adults in Europe and North America (with almost 100,000 participants) and four adolescent cohorts (with about 8,500 participants), along with data from the International Consortium for Blood Pressure.

Michael Holick, MD, PhD, of Boston University, told MedPage Today that the study’s results didn’t come as a surprise. “There’s a lot of evidence pointing in the direction that vitamin D plays a role in improving cardiovascular health, including risk of hypertension,” he said.

The study is timely, because there’s been a discrepancy between findings of observational effects of vitamin D — which have been strong — and the weaker effects found in trial results, according to an accompanying commentary by Børge G. Nordestgaard, PhD, and Shoaib Afzal, MD, PhD, both of the University of Copenhagen in Denmark.

But the study also had some limitations; for instance, the researchers couldn’t completely rule out that some results were due to chance. Nordestgaard and Afzal urged caution in interpretation of the data.

Although the study “is an important step towards delineation of the role of low vitamin D concentrations in the pathogenesis of hypertension, much remains unknown,” they said. “Confirmation of these results in independent, similarly powered studies will be necessary, as will evidence of a corresponding benefit for the prevention of diseases caused by hypertension such as stroke.”