17/01/2026
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, according to a preliminary study presented at the American Heart Association’s Scientific Sessions 2025. The meeting held on November 7-10 in New Orleans, was a premier global exchange of the latest scientific advancements, research and evidence-based clinical practice updates in cardiovascular science.
Previous studies found low vitamin D levels are linked to worse heart health. The TARGET-D randomised clinical trial included 630 adults with heart disease who also had a previous heart attack. More than 85% of participants began the study with vitamin D levels in their blood below 40 ng/mL (100 nmol/L). 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 Heidi T. 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 to 80 ng/mL.”
Participants in the TARGET-D study were randomised to two groups: The standard of care group did not receive management of their vitamin D levels, and the treatment group received tailored vitamin D supplementation, with doses adjusted every three months until their vitamin D blood levels were above 40 ng/mL. Once the vitamin D level was above 40 ng/mL, levels were checked annually and doses adjusted if levels dropped below that target.
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 (200 nmol/L).
The study’s key findings include:
• People who received personalised dosing of vitamin D supplements to achieve vitamin D levels greater than 40 ng/mL for nearly four years had a 52% lower risk of heart attack compared to participants whose vitamin D levels were not managed.
• More than 85% of participants had vitamin D levels below 40 ng/mL when they enrolled in the study.
• Nearly 52% of participants in the treatment group required more than 5,000 IU of vitamin D each day to reach the target blood levels of greater than 40 ng/mL.
• There were no significant adverse outcomes from the vitamin D intervention
Researchers found that tailored vitamin D doses did not significantly reduce the primary outcomes of death, heart failure hospitalisation or stroke; rather, supplementation appeared to be beneficial for preventing heart attacks specifically.
For several years, informed by a broad reading of clinical and observational research, I have aimed for a minimum serum vitamin D level of 100 nmol/L (40 ng/mL) in my patients. In many cases, patients self-fund testing, as vitamin D measurement is often deprioritised in mainstream practice and higher target ranges are regarded as lacking clinical relevance beyond deficiency prevention.
This study provides important support for the clinical value of targeting higher vitamin D levels—an approach long adopted by many natural and integrative practitioners.
For more information see: https://bit.ly/49kHooj
and
https://newsroom.heart.org/news/heart-attack-risk-halved-in-adults-with-heart-disease-taking-tailored-vitamin-d-doses
