(Ivanhoe Newswire) -- Vitamin D deficiency in premenopausal women may increase the risk of developing systolic hypertension 15 years later, according to a new study. Researchers examined women enrolled in the Michigan Bone Health and Metabolism Study and analyzed data from 559 Caucasian women living in Tecumseh, MI. The study began in 1992 when the women were 24 to 44 years old, with an average age of 38 years.

Researchers took blood pressure readings annually throughout the study. They measured vitamin D blood levels once in 1993, and then compared their systolic blood pressure measurements in 2007.
 
Premenopausal women who had vitamin D deficiency in 1993 had three times the risk of developing systolic hypertension 15 years later, according to researchers. "This study differs from others because we are looking over the course of 15 years, a longer follow-up than many studies," Flojaune C. Griffin, M.P.H., co-investigator of the study and a doctoral candidate in epidemiology at the University of Michigan School of Public Health in Ann Arbor, was quoted as saying. "Our results indicate that early vitamin D deficiency may increase the long-term risk of high blood pressure in women at mid-life."

At the study onset, 2 percent of women had been diagnosed with hypertension, and an additional 4 percent had undiagnosed systolic hypertension. But 15 years later, 19 percent of the women had been diagnosed with hypertension, and an additional 6 percent had undiagnosed systolic hypertension, a significant difference.
Researchers controlled for age, fat mass, anti-hypertensive medication use, and smoking.

Researchers determined vitamin D status by measuring blood concentrations of 25-hydroxyvitamin D, which represents vitamin D storage in the body. This assessment in the blood reflects vitamin D obtained from ultraviolet B rays through sun exposure, vitamin D from foods such as fatty fish or fortified milk products and dietary supplements.

Vitamin D is either synthesized in the skin through exposure to ultraviolet B rays in sunlight or ingested as dietary vitamin D. Experts in the medical community generally agree that vitamin D deficiency among women is widespread. Researchers report many women don't get enough sunlight exposure to help keep vitamin D levels near to normal, nor do they have diets or take supplements that support normal levels of vitamin D, said Griffin.
However, Griffin said there is no general agreement about the optimal intake of vitamin D. Some researchers said the current recommended intake of 400 to 600 international units (IU) daily is inadequate and suggest a much higher daily intake, from 1,000 to 5000 IU.