A new study from Intermountain Health in Salt Lake City has found that giving heart attack patients personalized doses of vitamin D3 may reduce their risk of having another heart attack by 50%.
This breakthrough came from a large clinical trial where doctors closely tracked patients’ vitamin D levels and adjusted their supplements to reach healthy targets.
The study used a “target-to-treat” method, which means patients’ blood levels of vitamin D were monitored, and their vitamin D3 doses were increased or decreased to reach a safe and effective level.
These results were shared on November 9 at the 2025 American Heart Association Scientific Sessions in New Orleans.
Dr. Heidi May, the study’s lead researcher and a cardiovascular epidemiologist at Intermountain Health, called the results exciting.
She said that patients did not experience any negative side effects from taking higher doses of vitamin D3, and their risk of another heart attack was cut in half. However, she also emphasized that more research is needed to confirm these findings.
This study is important because low vitamin D levels are very common around the world. About half to two-thirds of people have lower-than-recommended levels.
In the past, most people got enough vitamin D from spending time in the sun. But today, many people avoid the sun due to skin cancer concerns, and that means they need to get their vitamin D from supplements.
Earlier studies showed that people with low vitamin D were more likely to have heart problems, but past clinical trials that gave everyone the same amount of vitamin D didn’t show clear benefits. The Intermountain researchers wondered if treating people based on their actual vitamin D levels would work better.
Dr. May said that older studies gave everyone vitamin D without checking if it actually helped their blood levels. In this new trial, called TARGET-D, doctors adjusted doses based on how well each person responded. That approach seems to have made a big difference.
The TARGET-D study began in 2017 and ran until 2023. It included 630 patients who had a heart attack within a month of signing up. The participants were followed through March 2025.
Half of the patients received no vitamin D treatment, while the other half had their vitamin D levels carefully managed. The goal was to raise their levels to above 40 nanograms per milliliter (ng/mL), a level considered healthy. At the beginning of the study, 85% of patients had vitamin D levels below that amount.
Most patients needed to take 5,000 international units (IU) of vitamin D3 per day, which is much higher than the usual 600-800 IU many people take. Patients with low levels were tested every three months and had their dose changed until they reached the target level. After that, they were tested once a year.
Researchers tracked serious heart problems such as strokes, heart failure, and death. Out of the 630 participants, 107 had a serious event. While the total number of heart-related problems was not very different between the two groups, those who received personalized vitamin D treatment were far less likely to have a second heart attack.
Next, the researchers plan to run a larger trial to confirm these results and see if this type of treatment can also prevent other heart conditions. Dr. May says that with more participants, they will be able to learn even more about how managing vitamin D levels can help heart patients stay healthier longer.
If you care about nutrition, please read studies about the best time to take vitamins to prevent heart disease, and vitamin D supplements strongly reduce cancer death.
For more information about nutrition, please see recent studies about plant nutrient that could help reduce high blood pressure, and these antioxidants could help reduce dementia risk.
Copyright © 2025 Knowridge Science Report. All rights reserved.
