Adults with heart disease who received vitamin D doses tailored to reach optimal blood levels reduced their risk of heart attack by 52% compared to those without vitamin D level management, 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 departure from previous vitamin D studies by personalizing supplementation based on individual blood test results rather than administering standard doses to all participants. More than 85% of the 630 study participants began the research with vitamin D levels below 40 ng/mL, a threshold many experts consider insufficient for optimal health. Nearly 52% of participants in the treatment group required more than 5,000 IU of vitamin D daily to reach target blood levels of 40-80 ng/mL, 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, explained the study's innovative approach. 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. We took a different approach by checking each participant's vitamin D levels at enrollment and throughout the study, adjusting their dose as needed to maintain them in the 40-80 ng/mL range. Researchers carefully monitored both vitamin D and calcium levels for participants in the treatment group throughout the study to prevent vitamin D toxicity. Doses were reduced or stopped if vitamin D levels rose above 80 ng/mL, as excessive vitamin D can lead to hypercalcemia, kidney failure and abnormal heart rhythm. While the tailored vitamin D supplementation showed significant benefit for preventing heart attacks specifically, it did not significantly reduce the primary outcome of death, heart failure hospitalization or stroke.
The study's limitations include its focus only on adults with diagnosed heart disease, meaning the results may not apply to people without heart conditions. Additionally, the relatively small number of participants limited analysis of other conditions and outcomes, and approximately 90% of participants self-identified as white, indicating the need for additional research across diverse populations. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal, as abstracts presented at American Heart Association scientific meetings are not peer-reviewed. May emphasized that these results could potentially improve patient care by focusing on blood tests for vitamin D levels and tailoring doses accordingly. However, she and her colleagues noted that more clinical trials are needed to determine whether targeted vitamin D treatment could help prevent heart disease before a first cardiac event. The American Heart Association encourages people with heart disease to consult their cardiologist before adding or changing any vitamin regimen.
