Reduced Vitamin D Levels Linked to Arterial Stiffness

Reduced Vitamin D Levels Linked to Arterial Stiffness

July 2011

A lack of vitamin D, even in generally healthy people, is linked with stiffer arteries and an inability of blood vessels to relax, research from Emory/Georgia Tech Predictive Health Institute has found. The results add to evidence that lack of vitamin D can lead to impaired vascular health, contributing to high blood pressure and the risk of cardiovascular disease. The study was presented at the Annual American College of Cardiology Meeting.

Dr. Ibhar Al Mheid, along with Arshed Quyyumi, MD, evaluated data from participants in the Emory/Georgia Tech study. Endothelial function was evaluated via brachial artery flow-mediated dilation, and microvascular function and arterial stiffness were assessed. Blood samples were analyzed for serum 25-hydroxyvitamin D, a form of the vitamin that reflects dietary intake and skin protection.

Study participants who increased their vitamin D levels were able to improve vascular health and lower their blood pressure. The 554 participants in the study were Emory or Georgia Tech employees—average age 47 and generally healthy—who are members of the Center for Health Discovery and Well Being.

The average level of 25-hydroxyvitamin D in participants' blood was 31.8 nanograms per milliliter. In this group, 14% had 25-hydroxyvitamin D levels considered deficient—less than 20 nanograms per milliliter—and 33% had levels considered insufficient—less than 30 nanograms per milliliter.

The researchers monitored the ability of participants' blood vessels to relax by inflating and then removing a blood pressure cuff on their arms. To allow blood to flow back into the arm, blood vessels must relax and enlarge—a change that can be measured by ultrasound. The researchers also made other measurements of smaller blood vessels and examined the resistance to blood flow imposed by the arteries.

Even after controlling for factors such as age, weight and cholesterol, people with lower vitamin D levels still had stiffer arteries and impaired vascular function, according to Dr. Al Mheid, a cardiovascular researcher at Emory University School of Medicine. "We found that people with vitamin D deficiency had vascular dysfunction comparable to those with diabetes or hypertension,” Dr. Al Mheid said.

Throughout the body, a layer of endothelial cells lines the blood vessels, controlling whether the blood vessels constrict or relax and helping to prevent clots that lead to strokes and heart attacks. Referring to the actions of vitamin D, Dr. Al Mheid said: "It could be strengthening endothelial cells and muscles surrounding the blood vessels. It could also be reducing the level of angiotensin, a hormone that drives increased blood pressure, or regulating inflammation.”

Participants whose vitamin D levels increased over the next six months, either from dietary supplements or ample sun exposure, tended to improve their measures of vascular health and had lower blood pressure. Forty-two study participants with vitamin D insufficiency whose levels later went back to normal had an average drop in blood pressure of 4.6 millimeters mercury.

Annual American College of Cardiology Meeting