A decades-long study of more than 7,000 Japanese-American men in Hawaii has yielded valuable insight into the possible connection between a lack of vitamin D and increased risk of stroke later in life.

The results of the study were reported today in the medical journal “Stroke,” published by the American Heart Association.

Gotaro Kojima, lead author of the study and geriatric medicine fellow at the University of Hawaii’s John A. Burns School of Medicine, said the study “confirms that eating foods rich in vitamin D might be beneficial for stroke prevention.”

The study tracked 7,385 Japanese-American men living on Oahu who were part of the Kuakini Honolulu Heart Program. All were between the ages of 45 and 68 years when the study began in 1965.

The participants were divided into four groups according to the amount of vitamin D they had consumed. Researchers tracked the participants’ health records through 1999 to determine the incidence of stroke.

The study found that participants who consumed the least dietary vitamin D had a 22 percent higher risk of stroke and a 27 percent higher risk of ischemic (blood-clot-related) stroke compared to those who consumed the highest levels of vitamin D. (Researchers adjusted the findings for age, total calorie intake, body-mass index, hypertension and other significant health factors.)

Vitamin D is a nutrient that can prevent rickets in children and bone loss in adults. It is also believed to lower a person’s risk of cancer, diabetes and other diseases.

Vitamin D is absorbed from sunlight, but this process becomes more difficult as people age, Kojima said. People can supplement their vitamin D intake by consuming fortified milk and breakfast cereals, fatty fish and egg yolks.

Kojima said it is unclear whether the results of the study could b applied to different ethnic groups or to women.