Low levels of vitamin D are associated with an increased risk of high blood pressure in women, say US researchers.
Previous research has suggested that higher levels of vitamin D and exposure to the sun – the major source of vitamin D – are associated with lower blood pressure, but there is a lack of data supporting the association, explain Dr John Forman and colleagues from Harvard Medical School in Boston, Massachusetts.
To investigate further, the team examined data on 1484 women, aged between 32 and 52 years, who participated in a long-term health study that started in 1989. None of the women had high blood pressure at enrolment.
All of the women supplied blood samples between 1997 and 1999 and were monitored until 2005, during which time 750 developed high blood pressure.
Analysis revealed women who developed high blood pressure had, on average, significantly lower levels of vitamin D than those who did not develop the condition.
After accounting for age, body mass index, physical activity levels, family history of high blood pressure and other factors, the researchers found that women with the lowest levels of vitamin D were 66% more likely to develop high blood pressure than those with the highest levels of the vitamin.
Furthermore, compared with women with “adequate” levels of vitamin D, those who had vitamin D deficiency (less than 30 ng/ml) were 47% more likely to develop high blood pressure.
Writing in the journal Hypertension, Dr Forman and team conclude that low levels of vitamin D “are independently associated with a higher risk of incident hypertension [high blood pressure]”.
They add: “Given the high prevalence of vitamin D deficiency plus the availability of relatively cheap and effective interventions to raise [vitamin D] levels, these results could have substantial public health implications.
“Our findings should be tested in randomised trials to determine whether vitamin D supplementation could be effective in reducing blood pressure.”