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 reach optimal blood levels reduced their risk of heart attack by more than half compared to those who did not have their vitamin D levels optimized, according to preliminary research from the TARGET-D randomized clinical trial. The study, to be presented at the American Heart Association's Scientific Sessions 2025, found that participants who achieved vitamin D blood levels above 40 ng/mL through personalized dosing had a 52% lower risk of heart attack over nearly four years of follow-up.

The TARGET-D trial included 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. Unlike previous vitamin D studies that used standard doses for all participants, this trial personalized supplementation based on individual blood test results. More than 85% of participants began the study with vitamin D levels below 40 ng/mL, a level many experts consider insufficient for optimal health.

Heidi T. May, Ph.D., M.S.P.H., FAHA, principal investigator of TARGET-D and an epidemiologist at Intermountain Health, explained the novel 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." Participants in the treatment group received dose adjustments every three months based on blood testing, while the standard care group received no vitamin D monitoring.

The study revealed that nearly 52% of participants in the treatment group required more than 5,000 IU of vitamin D daily to reach target blood levels. This dosage exceeds the FDA-recommended daily intake of 800 IU by more than six times. Researchers carefully monitored both vitamin D and calcium levels throughout the study to prevent vitamin D toxicity, which can lead to hypercalcemia, kidney failure and abnormal heart rhythm.

While the personalized vitamin D approach significantly reduced heart attack risk, it did not significantly affect the primary outcome of death, heart failure hospitalization or stroke. A total of 107 major cardiac events occurred during the study period, with 15.7% in the treatment group and 18.4% in the standard care group. The American Heart Association encourages people with heart disease to consult their cardiologist before adding or changing any vitamin regimen.

The study has several limitations, including that it only included adults with diagnosed heart disease, so results may not apply to people without heart disease. Additionally, 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. More information about the study can be found in the abstract available through the American Heart Association's Scientific Sessions 2025 Online Program Planner at https://professional.heart.org/en/meetings/scientific-sessions.

May emphasized that these results could improve patient care by focusing on blood tests for vitamin D levels and tailoring doses accordingly. The researchers noted that more clinical trials are needed to determine whether targeted vitamin D treatment could help prevent heart disease before a first cardiac event occurs. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.