The American Heart Association has announced results from a preliminary study on heart health due to be presented at the company's Scientific Sessions 2025.
Adults with heart disease who had a previous heart attack and took vitamin D doses tailored to reach optimal blood levels reduced their risk of another heart attack by more than half compared to those who did not have their vitamin D blood levels optimised, according to the study.
Blood levels considered optimal for heart health are between 40-80 ng/mL.
Key findings
- Participants with personalised vitamin D dosing to maintain blood levels above 40 ng/mL for had a 52% lower risk of heart attack,
- More than 85% of participants started the study with vitamin D levels below 40 ng/mL,
- Around half (52%) of the treatment group needed more than 5000 IU daily to reach target levels — more than six times the FDA’s recommended 800 IU,
- While personalised dosing did not reduce overall rates of death, stroke or heart failure, it showed a specific benefit in lowering heart attack risk.
Previous studies have found that low vitamin D levels are linked to worse heart health.
The TARGET-D randomised clinical trial included adults with heart disease who also had a previous heart attack to determine whether achieving optimal vitamin D blood levels could prevent future heart attacks, strokes, heart failure hospitalisations or deaths.
Unlike earlier vitamin D randomised trials that used standard doses, the TARGET-D trial personalised the doses based on the results of each participant’s blood test.
“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 Dr Heidi May, principal investigator of TARGET-D and an epidemiologist and professor of research at Intermountain Health in Salt Lake City, Utah.
“We took a different approach. We checked each participant's vitamin D levels at enrolment and throughout the study and we adjusted their dose as needed to bring and maintain them in a range of 40-80 ng/mL.”
Researchers monitored both vitamin D and calcium levels for the 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.
Excessive vitamin D can lead to hypercalcaemia (higher-than-normal levels of calcium in the blood), kidney failure and abnormal heart rhythm.
May says that these results could improve patient care by focusing on blood tests for vitamin D levels and tailoring doses.
“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 added.
May and her study colleagues emphasised that more clinical trials are needed to determine whether targeted treatment with vitamin D could help prevent heart disease before a first cardiac event.