Younger white women with vitamin D deficiencies are about three times more likely to have high blood pressure in middle age than those with normal vitamin levels, according to a study released on Thursday.
The study, presented at a meeting of the American Heart Association in Chicago, adds younger women to a growing list of people including men who may develop high blood pressure at least in part because of low vitamin D.
Researchers in Michigan, who examined data on 559 women beginning in 1992, found that those with low levels of vitamin D were more likely to have high blood pressure 15 years later in 2007.
Our results indicate that early vitamin D deficiency may increase the long-term risk of high blood pressure in women at mid-life, said Flojaune Griffin, who worked on the study for the University of Michigan School of Public Health.
Vitamin D, which the human body can make from sunlight and which is found in fatty fish, fortified milk products and dietary supplements, has long been known to contribute to healthy bones and teeth.
But deficiencies, which are widespread in women, are linked to cancer, immune system problems and inflammatory diseases.
High blood pressure raises the likelihood of stroke, heart disease and other cardiovascular problems.
The women in the blood pressure study lived in Tecumseh, Michigan, and were 24 to 44 years old with an average age of 38, when the research began.
Researchers measured vitamin D blood levels at the outset and took blood pressure readings once a year. In 2007, they compared systolic readings -- the top number in blood pressure results that indicates the pressure within blood vessels when the heart beats.
More than 10 percent of women with vitamin D deficiencies had high blood pressure in 2007, versus 3.7 percent of those with sufficient levels. When the study began, 5.5 percent with deficiencies also had high blood pressure, compared to 2.8 percent with normal vitamin D.
The study was funded by the U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases.
Almost half the population worldwide has lower-than-optimal levels of vitamin D and researchers say the problem is worsening as people spend more time indoors. African-Americans seem at especially high risk as dark skin can make it harder for the body to absorb ultraviolet light.