Having too little vitamin D has been linked
to an increased risk of heart disease, a US study has
The Harvard Medical School team said
the risk was particularly high for those who also had
high blood pressure.
Writing in the journal Circulation, they
said correcting vitamin D deficiency could be beneficial.
A British Heart Foundation spokeswoman
said more information was needed on how the vitamin affected
Blood pressure link
Vitamin D is mainly obtained from exposure
to the sun, as well as from certain foods such as oily
fish and eggs.
There are concerns that many people,
including the elderly, pregnant women and those who wear
all-concealing clothing do not get enough of the vitamin.
A lack of the nutrient, already known
to cause weakened bones, has also been linked to multiple
sclerosis and rheumatoid arthritis.
The US study, which began in 1996, looked
at over 1,700 people with an average age of 59.
Their vitamin D levels were tested and
they were then monitored for up to seven years.
Those with low levels of vitamin D in
their blood, below 15 nanograms per millilitre (ng/ml),
had twice the risk of a heart attack, heart failure or
a stroke compared to those with higher levels (above 15ng/ml).
The highest incidence of cardiovascular
disease was seen in those with high blood pressure and
low vitamin D levels.
Overall, 28% of individuals had levels
of vitamin D below 15 ng/ml. Only 10% had levels above
30 ng/ml - considered ideal for bone health.
The researchers say that because receptors
for vitamin D are found in heart muscle and blood vessel
lining, low levels could be a contributing factor in heart
But Dr Thomas Wang, who led the research,
added: "What hasn't been proven yet is that vitamin D
deficiency actually causes increased risk of cardiovascular
"This would require a large randomised
trial to show whether correcting the vitamin D deficiency
would result in a reduction in cardiovascular risk."
Other studies looking at using different
vitamins to benefit heart health have not shown positive
But Dr Wang said: "Just because other
vitamins haven't succeeded doesn't preclude the possibility
of finding vitamins that might prevent cardiovascular
"Vitamins are easy to administer and
in general have few toxic effects."
June Davison, cardiac nurse at the British
Heart Foundation said: "This study suggests an association
with Vitamin D deficiency and an increased risk of heart
and circulatory disease.
"However, the reasons as to why this
happens are uncertain and further research is needed to
understand the mechanisms behind this."