A recent study published in the Journal of Clinical Endocrinology & Metabolism discovered a J-shaped association between vitamin D levels and mortality caused by cardiovascular disease.
Since cardiovascular disease is the leading cause of death globally, the same research team wanted to determine the relationship between vitamin D levels and mortality specific to cardiovascular disease.
The researchers analyzed data from the Copenhagen General Practitioners Laboratory (CopD). The CopD database contains data from 247,574 citizens from the Copenhagen area from 2004 to 2010. This data included vitamin D measurements and causes of death.
Over the span of seven years, 16,645 participants died, with a total of 5,454 individuals dying from cardiovascular disease.
The researchers evaluated the relationship between mortality and vitamin D levels. Here is what they found:
- A vitamin D status of 28 ng/ml was associated with the lowest cardiovascular disease mortality risk.
- Among individuals who died from cardiovascular disease, 78.2% had levels below 28 ng/ml.
- Those with vitamin D levels around 4.8 ng/ml were 2.0 times more likely to die from cardiovascular disease than those with vitamin D levels of about 28 ng/ml.
- Those with vitamin D levels of about 50 ng/ml were 1.3 times more likely to die of cardiovascular disease than those with levels around 28 ng/ml.
The researchers concluded,
“Both low and high serum 25-hydroxyvitamin D levels were associated with increased cardiovascular disease mortality as well as mortality from stroke and acute myocardial infarction.”
This study proposes interesting findings that should not be ignored; however, they should be interpreted carefully. First of all, as with any observational study, this study does not prove causation. Also, vitamin D levels were only measured once over the span of seven years. Levels could have easily fluctuated over this long duration.
A possible explanation for these puzzling results could be that healthy vitamin D levels are important to maintain throughout life, beginning at an early age. A recent study found that vitamin D status during adolescence affects the risk of adult atherosclerosis, suggesting that vitamin D levels play a vital role in heart health starting at an early age. In this study, the average age of the participants was 51.
Further observational studies should measure vitamin D levels throughout the study, beginning at an early age to provide more insight.