New genetic research provides compelling
evidence that low levels of vitamin D have a causal role in the development of
high blood pressure (hypertension). The findings, published in The Lancet
Diabetes & Endocrinology, suggest that vitamin D supplementation could be
effective in combating some cases of hypertension.
"In view of the costs and side
effects associated with antihypertensive drugs, the potential to prevent or
reduce blood pressure and therefore the risk of hypertension with vitamin D is
very attractive", explains study leader Professor Elina Hyppönen from the
University of South Australia.
There has been considerable interest in
the role of vitamin D in hypertension, but until now, a direct causal link has
not been shown. Results from observational studies have suggested a strong
association between low vitamin D levels and increases in blood pressure and
hypertension, but randomised trials have not provided consistent evidence.
This Mendelian randomisation study used
genetic data from the D-CarDia collaboration, involving over 146 500
individuals of European ancestry from across Europe and North America.
Researchers used two common genetic
variants that affect circulating 25-hydroxyvitamin D or 25(OH)D concentrations
(which are generally used to determine a person's vitamin D status), to measure
the causal effect between vitamin D status and blood pressure and hypertension
risk. They found that for each 10% increase in 25(OH)D concentration there was
a drop in diastolic blood pressure (-0.29 mm Hg) and systolic blood pressure
(-0.37 mm Hg), and an 8.1% decrease in the odds of developing hypertension.
According to Professor Hyppönen,
"Mendelian randomisation helps to determine cause and effect because by
using genetic data we can better avoid confounding, reverse causation, and
bias. However, because we cannot exclude the possibility that our findings were
caused by chance, they need to be replicated in an independent, similarly
powered study. Further studies using randomised controlled trials are also
needed to confirm causality and the potential clinical benefits of vitamin D
supplementation."*
Writing in a linked Comment, Dr Shoaib
Afzal and Dr Børge Nordestgaard from Copenhagen University Hospital and the
University of Copenhagen in Denmark say, "Although [this] study is an
important step towards delineation of the role of low vitamin D concentrations
in the pathogenesis of hypertension, much remains unknown. 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. Finally, randomised intervention trials will be
needed to determine whether vitamin D supplementation can be used to prevent or
treat hypertension before such a strategy can be used clinically."
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