Adults with heart disease who received vitamin D doses tailored to achieve optimal blood levels had a 52% lower risk of heart attack compared to those without such management, according to preliminary research presented at the American Heart Association’s Scientific Sessions 2025. The TARGET-D randomized clinical trial, conducted at Intermountain Medical Center in Utah, enrolled 630 adults with acute coronary syndrome and followed them for an average of 4.2 years.
More than 85% of participants began the study with vitamin D levels below 40 ng/mL, a threshold many experts consider insufficient for optimal health. Unlike previous vitamin D trials that used standard doses, TARGET-D personalized supplementation based on periodic blood tests. Participants in the treatment group received dose adjustments every three months until their vitamin D levels reached 40-80 ng/mL, with annual monitoring thereafter. Nearly 52% of those in the treatment group required more than 5,000 IU of vitamin D daily—over six times the FDA's recommended daily intake of 800 IU—to reach target levels.
“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,” said Heidi T. May, Ph.D., M.S.P.H., FAHA, principal investigator and epidemiologist at Intermountain Health. “We checked each participant's vitamin D levels at enrollment and throughout the study, and adjusted their dose as needed to bring and maintain them in a range of 40-80 ng/mL.”
The study primarily assessed major cardiac events including heart attack, stroke, heart failure hospitalization, and death. While tailored vitamin D did not significantly reduce the composite outcome, it specifically cut heart attack risk by more than half. Researchers monitored vitamin D and calcium levels to prevent toxicity, reducing or stopping doses if levels exceeded 80 ng/mL. Excessive vitamin D can lead to hypercalcemia, kidney failure, and abnormal heart rhythm.
May noted that these results could improve patient care by encouraging blood testing for vitamin D levels and individualized dosing. “We encourage people with heart disease to discuss vitamin D blood testing and targeted dosing with their health care professionals to meet their individual needs,” she said. The American Heart Association advises consulting a cardiologist before changing vitamin regimens.
The study had limitations: it included only adults with heart disease, so results may not apply to others. Most participants were white (90%), and the smaller sample size limited analysis of other outcomes. Further trials are needed to determine if targeted vitamin D can prevent first cardiac events. The findings are considered preliminary until published in a peer-reviewed journal. For more information, see the abstract in the American Heart Association’s Scientific Sessions 2025 Online Program Planner.
