Vitamin D deficiency linked to increased heart risk

The ‘sunshine’ vitamin is once again in the news.

Recent studies have indicated that vitamin D may help to prevent cancer, strengthen bones, slow aging and ward off Tuberculosis. And now, according to a study at Harvard Medical school, people with a vitamin D deficiency could face up to twice the risk of a heart attack or stroke than those with higher levels of the vitamin.

The study, published in the journal Circulation, suggests that people with moderate to severe vitamin D deficiency have a risk “above and beyond” other well known cardiovascular risk factors such as high cholesterol and diabetes.

And for people with both high blood pressure and vitamin D deficiency, the risk appears especially high. When researchers isolated 688 study participants who had blood pressure, they found that this group had twice the risk of cardiovascular problems as other participants.

“Vitamin D deficiency is associated with increased cardiovascular risk, above and beyond established cardiovascular risk factors,” said lead author Dr. Thomas J. Wang, assistant professor of medicine at Harvard Medical School. “The higher risk associated with vitamin D deficiency was particularly evident among individuals with high blood pressure.”

The study, which involved 1,739 people with an average age of 59, was conducted between 1996 and 2001. After high cholesterol, diabetes and other risk factors were taken into account, people with lower vitamin D levels (below 15 nanograms per millilitre) had a 62 per cent increased risk of developing cardiovascular problems such as a heart attack, heart failure or stroke in the five years following than those with higher blood levels of the vitamin.

“We found that people with low vitamin D levels had a higher rate of cardiovascular events over the five-year follow-up period,” Dr. Wang said. “These results are intriguing and suggestive but need to be followed up with further study.”

More study needed
What hasn’t been proven yet is that vitamin D deficiency actually causes increased risk of cardiovascular disease, according to Wang. Previous smaller studies have suggested people with heart disease are more likely to have vitamin D deficiencies, though Wang says it’s hard to tell from the studies what came first, the heart trouble or the vitamin deficiency.

What is needed is “a large randomized trial to show whether correcting the vitamin D deficiency would result in a reduction in cardiovascular risk,” he said.

During the past decade, researchers have studied several other vitamins that initially showed promise in reducing heart disease. But the vitamins didn’t reduce heart disease in subsequent large randomized trials.

“On the flip side, just because other vitamins haven’t succeeded doesn’t preclude the possibility of finding vitamins that might prevent cardiovascular disease,” Wang said. “This is always an area of great interest. Vitamins are easy to administer and in general have few toxic effects.”

Vitamin D deficiency widespread
One-third to one-half of otherwise healthy middle-aged and older adults in developed countries are deficient in vitamin D, experts say. The Harvard study could “raise the possibility that treating vitamin D deficiency, via supplementation or lifestyle measures, could reduce cardiovascular risk,” Dr. Wang said, adding that many people don’t take in enough vitamin D “even for the purpose of achieving good bone health.”

“Low levels of vitamin D are highly prevalent in the United States, especially in areas without much sunshine,” he added. “Twenty to 30 percent of the population in many areas has moderate to severe vitamin D deficiency.”

Most of this is attributed to lack of sun exposure, pigmented skin that prevents penetration of the sun’s rays and inadequate dietary intake of vitamin D enriched foods, researchers said.

Food sources of vitamin D include milk, salmon, mackerel, sardines, cod liver oil and some fortified cereals.

Last year, the Canadian Cancer Society recommended adult Canadians take 1,000 international units (IU) of vitamin D daily to lower their cancer risk. The unprecedented move followed a U.S. study suggesting post-menopausal women who took a combination of vitamin D and calcium had a 60 per cent lower risk of breast, lung and colon cancer. (Read more.)

Also, the Canadian Paediatric Society recommended that pregnant or breast-feeding women consult their doctor about taking a supplement of 2,000 IU of vitamin D each day, especially during the winter months, to protect their babies.

Source: American Heart Association news release

Read the study.