A new study shows that giving heart attack survivors a personalized plan to manage their vitamin D3 levels could cut their chances of having another heart attack by 50%.
The research, led by Intermountain Health in Salt Lake City, was presented at the American Heart Association’s 2025 Scientific Sessions in New Orleans.
The study used a special “target-to-treat” method. Instead of giving everyone the same amount of vitamin D, doctors regularly tested patients’ blood levels and adjusted their vitamin D3 doses to reach a healthy level. This helped them avoid under- or over-treatment and gave more precise results.
Dr. Heidi May, the lead researcher, said the findings were exciting. “We didn’t see any bad side effects, even with higher doses of vitamin D3,” she explained. “And we saw a huge drop in the risk of having another heart attack.”
Vitamin D is a vital nutrient that our bodies need to stay healthy, especially for our bones and heart. In the past, people got enough of it from sunlight, but now, with more people spending time indoors or avoiding too much sun, many people need supplements. In fact, studies show that between half and two-thirds of people around the world have low vitamin D levels.
Older studies showed that low vitamin D is linked to heart problems, but when people were given the same small dose of vitamin D, it didn’t help much. That’s why the Intermountain team tried something different. They wanted to see if adjusting each patient’s dose until they reached the ideal level would make a bigger difference.
The study, called the TARGET-D trial, ran from 2017 to 2023 and followed patients until early 2025. It included 630 people who had recently had a heart attack. Half of them received no vitamin D treatment.
The other half had their blood vitamin D levels measured and adjusted to reach at least 40 nanograms per milliliter (ng/mL). At the start, most patients had levels below this number.
In the treatment group, many people needed high doses—around 5,000 international units (IU) per day—compared to the typical 600 to 800 IU found in standard supplements. Patients with healthy vitamin D levels were tested once a year. If their levels were low, they were checked every three months and their dose was adjusted until they hit the goal.
Over time, the researchers tracked serious health issues such as second heart attacks, strokes, hospital visits for heart failure, and deaths. Out of 630 people in the study, 107 experienced one of these major events.
The total number of events was about the same in both groups. However, people who received the personalized vitamin D treatment were half as likely to have a second heart attack.
These early results are promising, and the researchers now plan to run a larger study to confirm them. They hope to learn whether this personalized treatment can also reduce other heart problems.
Dr. May says that if these results are confirmed, the new approach could help many people around the world live longer, healthier lives after a heart attack.
If you care about heart health, please read studies about how eating eggs can help reduce heart disease risk, and herbal supplements could harm your heart rhythm.
For more health information, please see recent studies about how drinking milk affects risks of heart disease and cancer, and results showing strawberries could help prevent Alzheimer’s disease.
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