The study doesn't prove that low vitamin D levels place patients at higher risk of dying. Even if the findings are confirmed, low levels of vitamin D may be a marker for some other damaging factor.
The hope is that vitamin D supplements may be able to improve outcomes among people with heart failure, but this still needs to be put to the test.
Vitamin D is best known for helping the body absorb calcium, which restores and strengthens bone, protecting against fracture. But more and more studies suggest that low vitamin D levels are associated with the risk for a host of diseases, including certain cancers and kidney disease.
After several small studies linked low levels of vitamin D to poor outcomes in people with heart failure, Dutch researchers, led by Licette Liu, BSc, of the University Medical Center in Groningen, Netherlands, decided to start a larger study of 548 patients hospitalized with this condition.
Vitamin D and Heart Failure Patients
Patients were divided into three groups depending on their blood levels of vitamin D: low (below 29.6 nanomoles per liter), intermediate (29.6 to 43.9 nanomoles per liter), and high (above 43.9 nanomoles per liter).
Over the 18 months of follow-up, 165 patients died and 142 were hospitalized again. Those patients with the lowest vitamin D levels were 30% more likely to be hospitalized again or die than people with the highest levels. The effect of vitamin D levels held even after accounting for other factors.
The findings were presented at the annual congress of the European Society of Cardiology.
No one knows exactly why vitamin D may help heart health.
But it may have anti-inflammatory effects that may help keep blood vessels healthy, Liu says.
In the study, low levels of the vitamin were associated with high levels of C-reactive protein (CRP), a measure of inflammation activity.
This study was not designed to show whether supplementing heart failure patients with vitamin D would improve prognosis or even if it was safe to do. Until vitamin D pills are proven to improve outcomes among people with heart failure who have a deficiency, patients should not take supplements unless prescribed by a doctor, says American Heart Association past president Clyde Yancy, MD, medical director of the Baylor Heart and Vascular Institute at Baylor University Medical Center in Dallas.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.