SALT LAKE CITY — People who are deficient in vitamin D and raise their intake — through supplements or more sun exposure — can cut their risk for heart disease and a host of other chronic conditions, according to new research from Intermountain Medical Center.
Researchers found that raising the amount of vitamin D in the blood can help some people reduce the risk of heart disease by 30 percent. Recent studies have shown that as many as three-quarters of Americans have a concentration of vitamin D in their blood that is below normal.
"The question we looked at is, if you do something about it, like taking vitamin-D supplements, does that reduce the risk?" said Dr. J. Brent Muhlestein, the lead author of the study and director of cardiovascular research at Intermountain's Heart Institute. He and his colleague Dr. Heidi May found that "there is a reduced risk of cardiovascular death after patients knew their level was low and did something to normalize it."
More than 40,000 patient records were examined during two Intermountain Medical Center studies to come up with the new correlation. The research was presented publicly for the first time Monday during the American College of Cardiology's annual conference in Atlanta.
Muhlestein said the level of vitamin D that long has been recommended probably is not optimal. "If you want to eliminate any association between your level of vitamin-D levels and cardiovascular disease risk, you probably want to attain 43 (nanograms per milliliter of blood or higher)," he said.
In the study, patients who had those levels had lower rates of death, diabetes, cardiovascular disease, myocardial infarction, heart failure, high blood pressure, depression and kidney failure.
To date, a level of 30 nanograms of vitamin D per milliliter of blood has been considered "normal," he said.
For the first study, researchers followed two groups of patients for an average of one year. More than 9,400 patients, mostly female, reported low initial vitamin-D levels and had at least one follow-up exam during that time period. Researchers found that the 47 percent of the patients who increased their levels of vitamin D between the two visits showed a reduced risk for cardiovascular disease.
In the second study, researchers put more than 31,000 patients into three categories, based on their levels of vitamin D, and examined what happened to those who increased their vitamin D levels to 43 nanograms per milliliter of blood or higher.
Because the studies were not randomized trials, but a long-term examination of medical records for people whose vitamin-D level had been tested and found deficient, Muhlestein said he couldn't be sure if those who increased their vitamin-D intake took supplements, got more sun exposure or did both.
The studies found that about half of patients boosted their vitamin-D level after testing and the other half didn't.
The body makes vitamin D when exposed to ultraviolet B rays in sunlight, and recommendations for the exposure needed range from five to 30 minutes on the face, arms, back or legs (without sunscreen) twice a week.
Muhlestein estimates that about 66 percent of the population is vitamin-D deficient, based on the two studies.
Those who get their level tested and find it is very low can begin taking 5,000 units per day and then have the level checked again over time, he said. Most patients known to be deficient are taking somewhere between 2,000 and 5,000 units per day. Vitamin-D supplements, available in grocery or health stores, range from 1,000 to 10,000 units.
Muhlestein said because the study was an observational one, there may be confounding variables of which researchers aren't aware. "We don't know a lot about the patients, which complicates it," he said. "But it's still a very strong finding. Already, there is reason to treat someone who is deficient."
May said that, in the past, women have usually been tested for vitamin-D deficiency to see whether they need supplementation to boost bone health, since some suffer more often from osteoporosis than men. As a result, about 75 percent of those whose medical records were used in the study were female.
"In the past year to 18 months, there has been more coming out about the importance of vitamin D as a risk predictor," which means more men have been tested, May said. "As time goes on, I think you'll see some of the gender discrepancy (in testing) level out."
Contributing: Shari Roan, Los Angeles Times