High doses of vitamin D keep arteries more flexible, potentially warding off heart disease, heart attacks, and strokes, preliminary research suggests.

In just four months, vitamin D supplements reduced arterial stiffness in a group of 70 young black men and women in a small-scale clinical trial.

The flexibility of participants’ arteries improved even more with higher doses, said senior researcher Dr. Yanbin Dong, a professor with the Medical College of Georgia at Augusta University, in Augusta.

Human skin naturally synthesizes vitamin D when exposed to bright sunshine.

However, darker skin absorbs less sunlight, making black people more susceptible to vitamin deficiency, the researchers said.

In addition, body fat tends to capture and hold vitamin D, also contributing to deficiency.