Although observational studies have linked low vitamin D to increased cardiovascular risk, researchers say few randomized controlled trials have investigated the impact of vitamin D supplementation on cardiovascular disease outcomes.

Summary: Researchers at Beth Israel Deaconess Medical Center conducted a study to determine if higher doses of vitamin D supplementation could reduce markers of cardiac injury and strain in older adults with low vitamin D levels. Using data from the double-blind, randomized Study to Understand Fall Reduction and Vitamin D in You (STURDY), participants were given varying doses of vitamin D3 and followed over two years. The analysis revealed that vitamin D supplementation did not reduce cardiovascular disease markers, regardless of dosage or participants’ characteristics such as age, sex, or pre-existing conditions. These results suggest that vitamin D supplementation is not effective in lowering cardiovascular disease risk.

Key Takeaways:

  1. No Effect on Cardiac Markers: Higher doses of vitamin D supplementation did not reduce markers of cardiovascular disease over a two-year period, regardless of dose or participant characteristics.
  2. Low Vitamin D Linked, but Not Preventative: While low vitamin D levels were associated with elevated cardiac markers at baseline, supplementation did not prevent cardiovascular disease or reduce cardiac strain.
  3. Other Factors May Be at Play: Researchers suggest that factors such as outdoor physical activity may play a more significant role in cardiovascular disease prevention than vitamin D supplementation.

Cardiovascular disease is the primary cause of death among adults over age 65 years, and 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 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 does 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,” says lead author Katharine W. Rainer, MD, a resident physician at Beth Israel Deaconess Medical Center, in a release. “Our study decisively showed that vitamin D had no effect on the markers of cardiovascular disease over the two-year follow-up period, regardless of dose. These results reinforce evidence that vitamin D supplementation is not an effective intervention for cardiovascular disease prevention.”

Analyzing Levels of Vitamin D Supplementation

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, 1,000, 2,000, or 4,000 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.

Results

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 [cardiovascular disease], our study adds to the growing body of evidence that daily or monthly supplementation with vitamin D does not prevent [cadiovascular disease] events or reduce markers of subclinical cardiac injury or strain,” says corresponding and senior author Stephen P. Juraschek, MD, PhD, Research Director of the Hypertension Center at Beth Israel Deaconess Medical Center, in a release. “Instead, there may be other factors upstream to vitamin D and [cardiovascular disease] (such as outdoor physical activity, for example) that may be a better target for preventive interventions.”

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