Vitamin D Levels Linked With Health of Blood Vessels
ScienceDaily (Apr. 3, 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 the 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. Study participants who increased their vitamin D levels were able to improve vascular health and lower their blood pressure.
The data was presented by Ibhar Al Mheid, MD, a cardiovascular researcher at Emory University School of Medicine, at the annual American College of Cardiology meeting in New Orleans. Al Mheid is one of five finalists for the ACC's Young Investigators Award competition in physiology, pharmacology and pathology. He is working with Arshed Quyyumi, MD, professor of medicine and director of the Emory Cardiovascular Research Institute.
The 554 participants in the study were Emory or Georgia Tech employees -average age 47 and generally healthy -- who are taking part in the Center for Health Discovery and Well Being, part of the Emory/Georgia Tech Predictive Health Institute.
The average level of 25-hydroxyvitamin D (a stable form of the vitamin reflecting diet as well as production in the skin) in participants' blood was 31.8 nanograms per milliliter. In this group, 14 percent had 25-hydroxyvitamin D levels considered deficient, or less than 20 nanograms per milliliter, and 33 percent 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, Al Mheid says.
"We found that people with vitamin D deficiency had vascular dysfunction comparable to those with diabetes or hypertension," he says.
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.
"There is already a lot known about how vitamin D could be acting here," Al Mheid says. "It could be strengthening endothelial cells and the muscles surrounding the blood vessels. It could also be reducing the level of angiotensin, a hormone that drives increased blood pressure, or regulating inflammation."
Most Americans generally get the majority of their vitamin D from exposure to sunlight or from dietary supplements; fortified foods such as milk or cereals are a minor source. A few foods, such as oily fish, naturally contain substantial amounts of vitamin D.
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.
"This was an observational study, rather than an interventional one, and it was difficult to tease out how the people who restored their vitamin D levels got there," Al Mheid says. "We are hoping to conduct a study where we have participants take a defined regimen of vitamin D."
"With his findings showing the relationship between vitamin D deficiency and vascular dysfunction, Dr. Mheid has helped advance our understanding of the importance of Vitamin D in preventing a common health problem in aging adults," says Kenneth Brigham, MD, medical director of the Emory/Georgia Tech Center for Health Discovery and Well Being. "Additionally, ongoing health studies based on the Center's collection of health information from participants will yield more discovery as the Center continues to develop."
The Emory-Georgia Tech Predictive Health Institute is a national leader in moving the practice of medicine from a reactive, disease-focused system to a proactive health-focused system. The initiative integrates research, scholarship and education in an innovative effort aimed at revolutionizing care of people to define, preserve and prolong the health of individuals and of society.
Key areas of the Initiative include defining and measuring health using optimal biomarkers of health and understand their interrelationships, determining the best interventions to optimize health throughout an individual's or a population's lifetime.
High Levels of Vitamin D Appear to Lower Risk of Age-Related Macular Degeneration in Young WomenScienceDaily (Apr. 12, 2011) —
High levels of vitamin D in the bloodstream appear to be associated with a decreased risk of developing early age-related macular degeneration among women younger than 75 years, according to a report in the April issue of Archives of Ophthalmology, one of the JAMA/Archives journals.
"Age-related macular degeneration (AMD), a chronic, late-onset disease that results in degeneration of the macula, is the leading cause of adult irreversible vision loss in developed countries," the authors write as background information in the article. "Age-related macular degeneration affects approximately 9 percent (8.5 million) of Americans aged 40 years and older."
Amy E. Millen, Ph.D., of the School of Public Health and Health Professions, University at Buffalo, New York, and colleagues examined data from 1,313 women to investigate if serum 25(OH)D levels in the blood was associated with early age-related macular degeneration. "Serum 25(OH)D is the preferred biomarker for vitamin D status, as it reflects vitamin D exposure from both oral sources and sunlight." Women were participants of the Carotenoids in Age-Related Eye Disease Study, an ancillary study within the Women's Health Initiative Observational Study.
After adjusting for age and other known risk factors for AMD, no significant relationship was found between vitamin D status and early or advanced AMD. In women younger than 75 years (n=968), higher levels of serum 25(OH)D was associated with a significant decreased risk of early AMD, however in women 75 years and older (n=319), higher levels were associated with a borderline statistically significant increased risk.
In women younger than 75 years, intake of vitamin D from foods and supplements was associated with decreased risk of developing early AMD. Women who consumed the most vitamin D had a 59 percent decreased odds of developing early AMD compared with women who consumed the least vitamin D. The top food sources of vitamin D in the sample were milk, fish, fortified margarine and fortified cereal. No relationship was observed using self-reported time spent in direct sunlight.
"This is the second study to present an association between AMD status and 25(OH)D, and our data support the previous observation that vitamin D status may potentially protect against development of AMD," the authors conclude. "More studies are needed to verify this association prospectively as well as to better understand the potential interaction between vitamin D status and genetic and lifestyle factors with respect to risk of early AMD."