In people with low blood levels of vitamin D, boosting with supplements more than halved a person's risk of dying from any cause, compared to someone who remained deficient, according to a large new study.
Analysing data on more than 10,000 patients, University of Kansas researchers found that 70% were deficient in vitamin D and were at significantly higher risk for a variety of heart diseases.
D-deficiency also nearly doubled a person's likelihood of dying, whereas correcting the deficiency with supplements lowered their risk of death by 60%.
"We expected to see that there was a relationship between heart disease and vitamin D deficiency; we were surprised at how strong it was," Dr James L. Vacek, a professor of cardiology at the University of Kansas Hospital and Medical Center, said. "It was so much more profound than we expected."
Vitamin D deficiency has been linked to a range of illnesses, but few studies have demonstrated the reverse – that supplements could prevent those outcomes.
Dr Vacek and his team reviewed data from 10,899 adults whose vitamin D serum levels had been tested at the University of Kansas Hospital, and found that more than 70% of the patients were below 30 ng/ml.
After adjusting for the patients' medical history, medications and other factors, the cardiologists found that people with deficient levels of vitamin D were more than twice as likely to have diabetes, 40% more likely to have high blood pressure and about 30% more likely to suffer from cardiomyopathy than people without D deficiency.
Overall, those who were deficient in D had a three-fold higher likelihood of dying from any cause than those who weren't deficient, the researchers reported in the American Journal of Cardiology.
Lower risk of death
Moreover, when the team looked at people who took vitamin D supplements, their risk of death from any cause was about 60% lower than the rest of the patients, although the effect was strongest among those who were vitamin D deficient at the time they were tested.
Previous research has indicated that many Americans don't have sufficient levels of vitamin D. The latest National Health and Nutrition Examination Survey estimated that 25% to 57% of adults have insufficient levels of D, and other studies have suggested the number is as high as 70%.
Dr Vacek said he believes so many people are deficient because we should get about 90% of our Vitamin D from the sun and only about 10% from our food.
A sufficient amount of Vitamin D absorption from the sun would require at least 20 minutes of full-body exposure each day in warmer seasons, and most people aren't outside enough, Dr Vacek said. In the northern United States and throughout Canada, experts say the sun isn't strong enough during the winter months to make sufficient vitamin D, even if the weather was warm enough to expose the skin for a long time.
It means that adults should consider getting their Vitamin D levels checked through a simple blood test, Dr Vacek said, and take vitamin D supplements.
"If you're not deficient, Vitamin D is not a magic pill that will make you live longer," Dr Vacek said. "Its benefit is in people who are deficient. If you're low, it makes sense to be put on replacement therapy and have a follow-up a couple months later to make sure your levels come up."
(Reuters Health, Kimberly Hayes Taylor, November 2011)