Researchers led by Harald Dobnig, MD, of the Medical University of Graz, Austria, tracked 3,258 men and women who had been referred for an angiogram of their heart arteries. More than two-thirds had significant blockages in their coronary arteries.
The patients were followed for about eight years. During that time, 737 of them died, including 463 from cardiovascular problems.
Researchers found that people with the lowest levels of vitamin D in their blood had the highest chances of dying. Although chances of dying due to heart disease rose with decreasing levels of vitamin D, dying from other causes was more likely, too. Patients with little coronary artery disease were still much more likely to die during follow-up if they had low vitamin D levels.
It's not yet known whether low levels of vitamin D can trigger death from heart disease. Researchers say intervention trials using vitamin D could help establish if there is a causal relationship.
Global Low Vitamin D
In an article accompanying the research, the researchers report that on average both older and younger people around the world may not be getting enough vitamin D.
They speculate that it may be due to air pollution, a lack of outdoor activities, and increased urbanization, with more people staying and working indoors.
Vitamin D is naturally produced by your body when it is exposed to the sun, although sunscreens interfere with this process. As we age, vitamin D production slows down as well.
Lowdown on Low Vitamin D
Studies have shown that low levels of vitamin D are related to, among other things, heart disease, hypertension, and metabolic syndrome. In this study, researchers speculated that the vitamin may have anti-inflammatory effects that protect heart health.
They also believe it may affect how plaque is produced and builds up in the artery walls. The vitamin's anti-inflammatory properties may also be protective against a host of other diseases, including immune disorders and cancer.
Adequate levels of vitamin D are also essential for bone health, and low levels are associated with osteoporosis and fractures.
The study's researchers suggest that boosting vitamin D levels may be important to maintaining general good health. Because increasing sun exposure carries its own risks, doctors generally recommend increasing vitamin D levels through diet and supplements instead.
Just how much do you need? The recommended daily dose of vitamin D is 200 international units (IU) for people up to age 50, 400 IU for people aged 51 to 70, and 600 IU for people over age 70. But some medical professionals are suggesting that even higher levels may be needed for good health, from 1,000 to 2,000 IU a day.
The study appears in the June 23 edition of Archives of Internal Medicine.