Adults with heart disease who received vitamin D doses tailored to achieve optimal blood levels reduced their risk of heart attack by 52% compared to those who did not have their vitamin D levels managed, according to preliminary research to be presented at the American Heart Association's Scientific Sessions 2025. The TARGET-D randomized clinical trial represents a significant shift in approach to vitamin D supplementation, moving away from standard dosing toward personalized treatment based on individual blood levels.
The study enrolled 630 adults with acute coronary syndrome treated at Intermountain Medical Center in Utah from April 2017 to May 2023, with participants followed for an average of 4.2 years. Participants were randomly assigned to either a treatment group that received targeted vitamin D supplementation or a standard care group that did not receive vitamin D monitoring. The treatment approach involved checking vitamin D levels every three months and adjusting doses to maintain levels between 40-80 ng/mL, a range many experts consider optimal for heart health.
Heidi T. May, Ph.D., M.S.P.H., FAHA, principal investigator of TARGET-D and an epidemiologist at Intermountain Health, explained the study's innovative methodology. "Previous clinical trial research on vitamin D tested the potential impact of the same vitamin D dose for all participants without checking their blood levels first," May said. "We took a different 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."
The study revealed that more than 85% of participants began the research with vitamin D levels below 40 ng/mL, indicating widespread deficiency among adults with heart disease. Perhaps most notably, nearly 52% of participants in the treatment group required more than 5,000 IU of vitamin D daily to reach target blood levels—more than six times the FDA-recommended daily intake of 800 IU. Researchers monitored both vitamin D and calcium levels throughout the study to prevent vitamin D toxicity, reducing or stopping doses if levels exceeded 80 ng/mL.
While the tailored vitamin D approach showed significant benefit for heart attack prevention, it did not significantly reduce the primary outcome of death, heart failure hospitalization, or stroke. The study recorded 107 major cardiac events during the research period, with 15.7% occurring in the treatment group and 18.4% in the standard care group. The findings suggest that vitamin D's protective effects may be specific to heart attack prevention rather than providing broad cardiovascular protection.
The study's implications for clinical practice could be substantial, potentially shifting how healthcare providers approach vitamin D supplementation in patients with heart disease. May emphasized that these results could improve patient care by focusing on blood tests for vitamin D levels and tailoring doses accordingly. However, researchers caution that more clinical trials are needed to determine whether targeted vitamin D treatment could help prevent heart disease before a first cardiac event.
Several limitations warrant consideration when interpreting these findings. The study included only adults with diagnosed heart disease, so the results may not apply to people without cardiovascular conditions. The relatively small number of participants limited more comprehensive analysis of other conditions and outcomes. Additionally, the study population lacked diversity, with approximately 90% of participants self-identifying as white, indicating the need for additional research across different racial and ethnic groups.
As with all research presented at scientific meetings, these findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal. The American Heart Association maintains strict policies regarding scientific content and funding transparency, with detailed financial information available at https://www.heart.org/en/about-us/aha-financial-information. Before making any changes to vitamin regimens, the Association encourages people with heart disease to consult their cardiologists to discuss individual health needs and potential risks.
