Simin Liu, MD, ScD, professor of epidemiology, surgery, and medicine at Brown University, Providence, RI, and corresponding author of the meta-study, described some ways in which the RCTs differed from each other that caused them to arrive at different conclusions.

“Several main sources of heterogeneity in earlier studies that led to conflicting findings relating supplementation to cardiometabolic risk factors included ethnocultural background, age, body weight, and study participants’ circulating 25[OH]D levels at enrollment,” he said.

The level of serum 25[OH]D circulating in one’s blood is considered the most reliable indicator of the body’s total vitamin D supplyTrusted Source, including naturally produced vitamin D from the skin and from dietary supplements.

Jayne Morgan, MD, cardiologist and the Executive Director of Health and Community Education at the Piedmont Healthcare Corporation in Atlanta, GA, who was not involved in the meta-study, noted another reason the medical community is not as confident regarding vitamin D as one might hope.

“While there are a plethora of studies demonstrating a link between taking vitamin D and a lower risk of heart disease, there is still a lack of a direct cause and effect. Further, although low serum vitamin D levels are associated with increased cardiovascular risk, it remains unclear whether this is a cause or contributing factor to heart disease, or rather a consequence of heart disease.”
— Jayne Morgan, MD

Still, “Here is where the data is leaning but [there is] nothing definitive yet regarding cardiovascular endpoints. So while there is not the standard of evidence-based data here, it certainly reaches the metric of evidence-informed,” Morgan said.

“Further, there are benefits on bone health, muscle function, and reduced inflammation. It’s possible positive effects on both hypertension, diabetes, and lipids are worth watching as well,” she added.