If you're looking to improve your heart health, getting regular exercise and eating healthy foods can definitely help, but new research says popping a daily vitamin D supplement won't.
The research – a meta-analysis of 21 randomised clinical trials involving more than 83 000 people – found no decrease in major cardiovascular events in people taking vitamin D supplements. There was also no drop in heart attack rates. No drop in stroke. No drop in death from any cause.
Receptors for vitamin D
"Vitamin D supplementation didn't show any cardiovascular benefit," said the study's lead author, Dr Mahmoud Barbarawi. He's chief resident in the department of internal medicine at Hurley Medical Center at Michigan State University in Flint.
"There are a lot of things people can do to lower cardiovascular risk – doing regular exercise, healthy eating, stopping smoking, and controlling hypertension [high blood pressure] and diabetes. But giving vitamin D supplements for the sake of lowering cardiovascular risk is not recommended," Barbarawi said.
Previous studies had reported that people who had experienced a heart attack, stroke, heart failure and death from heart disease also had low vitamin D levels. The researchers said there are plausible biological reasons to believe that vitamin D levels might influence heart and blood vessel health. For example, some muscles in the blood vessels have receptors for vitamin D, the researchers noted.
To get a clear idea of how much vitamin D might help protect the heart, the investigators reviewed nearly two dozen randomised clinical trials. More than 41 000 people in these trials took vitamin D supplements, and another 41 000 took an inactive placebo.
The average age of the study participants was 66, and three-quarters of the study volunteers were women.
Vitamin D levels of the study participants varied by trial, Barbarawi said. The dose of the vitamin D supplements given also varied greatly, as did the length of the studies.
Barbarawi said the researchers were surprised to see that vitamin D supplements didn't appear to have any effect on major heart problems, stroke or death.
"We believe that low vitamin D is a marker for some sort of underlying disease, but that doesn't mean if we treat low vitamin D that it will protect the heart," he explained.
But if people are deficient in vitamin D (less than 12 ng/mL), it's still important to treat that deficiency, especially for bone health, Barbarawi added.
Findings from the study were published online in JAMA Cardiology.
Dr Arshed Quyyumi, co-author of an editorial accompanying the study, agreed that anyone with a vitamin D deficiency should take a supplement to prevent bone-related problems.
Quyyumi also agreed that there doesn't appear to be a reason to take vitamin D supplements to prevent cardiovascular disease. He said it's likely that other factors explain the link between heart disease and vitamin D levels.
For example, Quyyumi said, it's possible that people who have sedentary lifestyles may show signs of cardiovascular disease and low vitamin D. Not only would those folks not be getting heart-healthy exercise, they also would not get the sun exposure from exercising outdoors that causes the body to produce vitamin D.
Quyyumi said if you've been taking vitamin D supplements for heart disease, there doesn't appear to be any harm from low doses. But, because there appears to be no benefit for the heart, you can save some money by skipping the supplements.
Both experts said more studies would be helpful, especially in people who have a vitamin D deficiency. Barbarawi said it would also be beneficial to have larger studies looking specifically at how differing levels of the vitamin affect race, gender and ethnicity.
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