Cardiovascular disease (CVD) is the primary cause of death among adults over age 65 years. Seniors are also likely to have low blood levels of Vitamin D, which has been linked to cardiovascular disease. Despite this, many observational trials have not demonstrated that Vitamin D supplementation reduces cardiovascular disease risk.

To evaluate the effect of Vitamin D supplementation on the heart, researchers at Beth Israel Deaconess Medical Center (BIDMC) assessed whether higher doses of the vitamin reduced the presence of two specific proteins in the blood known to indicate cardiac injury and strain.

The team's analysis of data from a double-blind, randomized trial—the gold standard form of scientific testing that provides the most persuasive results—do not support the use of higher dose Vitamin D supplementation to reduce cardiovascular risk in adults with low blood levels of Vitamin D.

The study is published in the American Journal of Preventative Cardiology.

"While multiple observational studies have demonstrated a relationship between low Vitamin D and high risk for cardiovascular disease, few randomized controlled trials to date have evaluated the role of Vitamin D supplementation on cardiovascular disease," said lead author Katharine W. Rainer, MD, a resident physician at BIDMC.

"Our study decisively showed that Vitamin D had no effect on the markers of cardiovascular disease over the 2-year follow-up period, regardless of dose. These results reinforce evidence that Vitamin D supplementation is not an effective intervention for cardiovascular disease prevention."

Rainer and colleagues analyzed data from the Study to Understand Fall Reduction and Vitamin D in You (STURDY), a double-blind, randomized trial that tested the effects of Vitamin D3 supplementation on fall risk among adults 70 years or older with low Vitamin D concentration levels. A National Institute of Aging-sponsored trial, STURDY was conducted between July 2015 and March 2019.

Participants were randomized into one of four groups, receiving either 200, 1000, 2000, or 4000 international units (IU) per day of Vitamin D3 supplementation. Blood levels of the markers of cardiovascular disease were measured at baseline, and at three-, 12- and 24-month follow-up visits.

The investigators found that lower Vitamin D levels were associated with a baseline elevation in one marker of cardiovascular disease; however, Vitamin D supplementation failed to reduce either marker of cardiovascular disease over the two-year study period, regardless of dose. The findings were largely consistent regardless of participants' age, sex, race or participants' history of cardiovascular disease including high blood pressure and/or diabetes.

"While much work is needed to understand why Vitamin D deficiency is associated with CVD, our study adds to the growing body of evidence that daily or monthly supplementation with Vitamin D does not prevent CVD events or reduce markers of subclinical cardiac injury or strain," said corresponding and senior author Stephen P. Juraschek, MD, Ph.D., Research Director of the Hypertension Center at BIDMC.

"Instead, there may be other factors upstream to Vitamin D and CVD (such as outdoor physical activity, for example) that may be a better target for preventive interventions."