The same vitamin D deficiency that can result in weak bones has been associated with an increased risk of cardiovascular disease (CVD), according to a Framingham Heart Study report published Jan. 7 online in Circulation: Journal of the American Heart Association.
“Vitamin D deficiency is associated with increased cardiovascular risk, above and beyond established cardiovascular risk factors,” said Thomas J. Wang, MD, assistant professor of medicine at Harvard Medical School in Boston. “The higher risk associated with vitamin D deficiency was particularly evident among individuals with high blood pressure.”
In a study of 1,739 Framingham Heart Study participants (average age 59, all Caucasian), researchers found that those with blood levels of vitamin D below15 nanograms per milliliter (ng/mL) had twice the risk of a cardiovascular event such as a heart attack, heart failure or stroke in the next five years compared to those with higher levels of vitamin D.
When researchers adjusted for traditional cardiovascular risk factors such as high cholesterol, diabetes and high blood pressure, the risk remained significant with a 62 percent higher risk of a CV event in participants with low levels of vitamin D compared to those with higher levels.
Researchers observed the highest rate of cardiovascular disease events in subset analyses dividing 688 participants according to high blood pressure status. After researchers adjusted for conventional CV risk factors, participants with hypertension and a vitamin D deficiency had about 2 times the risk of having a CVD event in five years.
“We found that people with low vitamin D levels had a higher rate of cardiovascular events over the five-year follow-up period,” Wang said.
The study participants had no prior CVD and were tested for vitamin D status, and then followed for an average of 5.4 years.
The participants attended the examinations between 1996 and 2001, and researchers obtained medical histories, physical exams and laboratory assessments of vascular risk factors. They also obtained medical records related to CVD.
Overall, 28 percent of individuals had levels of vitamin D below15 ng/mL and 9 percent had levels below 10 ng/mL. Although levels above 30 ng/mL are considered optimal for bone metabolism, only 10 percent of the study sample had levels in this range, researchers said.
During follow-up, the authors found:
- 120 participants developed a first CV event including fatal and nonfatal coronary heart disease;
- 28 participants had fatal or nonfatal cerebrovascular events such as nonhemorrhagic stroke;
- 19 participants were diagnosed with heart failure; and
- 8 had occurrences of claudication, fatigue in the legs during activity.
Wang said that “20 to 30 percent of the population in many areas has moderate to severe vitamin D deficiency,” attributable to lack of sun exposure, pigmented skin that prevents penetration of the sun’s rays and inadequate dietary intake of vitamin D enriched foods.
“What hasn’t been proven yet is that vitamin D deficiency actually causes increased risk of cardiovascular disease. This would require a large randomized trial to show whether correcting the vitamin D deficiency would result in a reduction in cardiovascular risk,” the authors wrote.
Therefore, Wang and colleagues do not recommend physicians check for vitamin D deficiency or that those with a known vitamin D deficiency be treated to prevent heart disease at this time.
“On the flip side, just because other vitamins haven’t succeeded doesn’t preclude the possibility of finding vitamins that might prevent cardiovascular disease,” Wang said.
The National Institute of Health, the U.S. Department of Agriculture and American Heart Association funded the study.