Nov. 16, 2009 (Orlando, Fla.) -- Some men with low levels of vitamin D in their blood are at particularly high risk of developing heart disease and weakened bones that can lead to osteoporosis, researchers report.
In a study of more than 1,000 men, those with low levels of both vitamin D and the sex hormone estrogen were at significantly increased risk of having cardiovascular disease, says study head Erin Michos, MD, a cardiologist at Johns Hopkins.
Role of Estrogen and Vitamin D
The new findings build on previous studies showing that low levels of vitamin D and estrogen, a sex hormone found in differing amounts in men and women, are independent risk factors for developing plaque-laden arteries and weakened bones.
The new study confirmed that men who had low levels of estrogen were at increased risk of both heart disease and osteopenia.
And if both estrogen and vitamin D levels were depressed, the men's rates of heart and bone disease were even higher, Michos says.
Michos and colleagues now plan to analyze blood samples from women to see if the same results hold true for them. Studies are also under way to determine whether vitamin D supplements can cut the risk of heart attack, stroke, and osteoporosis.
The findings were presented at the annual meeting of the American Heart Association (AHA).
How to Get Enough Vitamin D
Previous research showed that 41% of men and 53% percent of women are deficient, with vitamin D levels below 28 nanograms per milliliter, Michos says.
The Institute of Medicine suggests that an adequate daily intake of vitamin D is between 200 and 400 international units for children and adults up to age 70. But Michos feels this is inadequate to achieve optimal nutrient blood levels.
Michos recommends that men and women boost their vitamin D levels by eating diets rich in fatty fish, such as cod, sardines, and mackerel. She also suggests consuming fortified dairy products, taking vitamin supplements, and briefly exposing skin to the sun's vitamin-D-producing ultraviolet light.
AHA spokeswoman Alice Lichtenstein, DSc, a nutritionist at Tufts University, says the new studies add to growing evidence suggesting a link between vitamin D insufficiency and cardiovascular disease.
But until well-designed studies show that vitamin D can improve heart health, people should refrain from taking mega-supplements on their own, she says.
"People sometimes think if a little is good, a lot is better. But that's not always true. Too much vitamin D can build up and be toxic to organs like the kidney," Lichtenstein says.
Low Levels of Vitamin D Linked to Stroke
Also at the meeting, Utah researchers reported that low levels of vitamin D may raise the risk of stroke, heart disease, and death.
The researchers followed 27,686 people, ages 50 and older, with no history of cardiovascular disease. The participants were divided into three groups based on their vitamin D levels: normal (more than 30 nanograms per milliliter), low (15 to 30 nanograms per milliliter), or very low (less than 15 nanograms per milliliter).
After one year, those with very low levels of vitamin D were 77% more likely to die, 45% more likely to develop heart disease, and 78% more likely to have a stroke, compared with people with normal vitamin D levels.
"We concluded that among patients 50 years of age or older, even a moderate deficiency of vitamin D levels was associated with developing coronary artery disease, heart failure, stroke and death," says researcher Heidi May, PhD, an epidemiologist with the Intermountain Medical Center in Murray, Utah.