NEW ORLEANS – A new study suggests a personalized approach to vitamin D supplementation could be a breakthrough for heart disease patients. Researchers found that tailoring vitamin D doses to achieve specific blood levels reduced the risk of a subsequent heart attack by 52% in adults with established heart disease.

The research, to be presented at the American Heart Association’s Scientific Sessions 2025, marks a significant shift from previous trials. Unlike earlier studies that used fixed doses for all participants, this study customized the dosage based on regular blood tests to maintain vitamin D levels within an optimal range.

“Previous clinical trial research on vitamin D tested the same dose for all participants without checking their blood levels first,” said lead investigator Dr. Heidi T. May, an epidemiologist at Intermountain Health in Salt Lake City. “We took a different approach. We adjusted the dose as needed to bring and maintain them in a target range.”

The study, named the TARGET-D trial, involved over 600 adults with heart disease. Strikingly, 85% of participants began the study with vitamin D levels below the target range of 40-80 ng/mL, which many experts consider insufficient for optimal health.

To reach the desired levels, more than half of the patients in the treatment group required daily doses exceeding 5,000 IU—more than six times the FDA’s standard daily recommendation of 800 IU.

Key Findings and Cautions

The most dramatic result was a 52% lower risk of heart attack in the group receiving personalized vitamin D doses over nearly four years, compared to those who did not. However, the tailored supplementation did not significantly reduce the overall risk of a combined endpoint that included stroke, heart failure hospitalization, or death.

Researchers emphasize that the findings are preliminary and await full publication in a peer-reviewed journal. They also caution against self-prescribing high doses of vitamin D.

“We encourage people with heart disease to discuss vitamin D blood testing and targeted dosing with their health care professionals,” Dr. May added. The study carefully monitored participants to prevent vitamin D toxicity, a potential risk with high doses.

The study’s limitations include its focus on patients who already had heart disease, meaning the results may not apply to the general population. Additionally, most participants were white, indicating a need for more diverse research.

For now, this study offers a promising new direction: that optimizing a simple vitamin through personalized medicine could provide powerful protection for vulnerable hearts.