VITAMIN D AND HYPERTENSION
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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