Tailored Vitamin D Doses Reduce Heart Attack Risk by 52% in Heart Disease Patients

Adults with heart disease who received vitamin D doses tailored to achieve optimal blood levels reduced their risk of heart attack by more than half compared to those without vitamin D level monitoring, according to preliminary research presented at the American Heart Association's Scientific Sessions 2025. The TARGET-D randomized clinical trial found that patients who maintained vitamin D levels above 40 ng/mL for nearly four years had a 52% lower risk of heart attack than participants whose vitamin D levels were not managed.

The study revealed that more than 85% of participants began the trial with vitamin D levels below 40 ng/mL, a level many experts consider insufficient for optimal health. Unlike previous vitamin D trials that used standard doses for all participants, the TARGET-D trial personalized supplementation based on individual blood test results. Nearly 52% of participants in the treatment group required more than 5,000 IU of vitamin D daily to reach target blood levels, which is more than six times the FDA-recommended daily intake of 800 IU.

Heidi T. May, Ph.D., M.S.P.H., FAHA, principal investigator of TARGET-D and an epidemiologist at Intermountain Health in Salt Lake City, Utah, explained the study's unique approach. "We checked each participant's vitamin D levels at enrollment and throughout the study, and we adjusted their dose as needed to bring and maintain them in a range of 40-80 ng/mL," May said. Researchers monitored both vitamin D and calcium levels for participants in the treatment group throughout the study to prevent vitamin D toxicity, reducing or stopping doses if levels rose above 80 ng/mL.

The study enrolled 630 adults with acute coronary syndrome treated at Intermountain Medical Center in Utah from April 2017 to May 2023, with an average follow-up of 4.2 years. Participants were randomly assigned to either a treatment group receiving targeted vitamin D supplementation or a standard care group without vitamin D monitoring. While tailored vitamin D doses did not significantly reduce the primary outcome of death, heart failure hospitalization or stroke, supplementation appeared specifically beneficial for preventing heart attacks.

These findings could significantly impact patient care by emphasizing the importance of blood testing for vitamin D levels and individualized dosing. The American Heart Association encourages people with heart disease to consult their cardiologist before adding or changing a vitamin regimen. Additional information about the study can be found in the American Heart Association's Scientific Sessions 2025 Online Program Planner.

The study had several limitations, including that it only included adults with diagnosed heart disease, so results may not apply to people without heart disease. Most participants were from the same racial group, with approximately 90% self-identifying as white, so additional research is needed to determine whether the results apply to people of all backgrounds. May and her colleagues emphasized that more clinical trials are needed to determine whether targeted vitamin D treatment could help prevent heart disease before a first cardiac event.