A new study from Intermountain Health in Salt Lake City has found that a personalized approach to vitamin D3 supplementation can make a big difference for people recovering from a heart attack.
Researchers discovered that carefully monitoring and adjusting patients’ vitamin D3 levels could reduce their chances of having another heart attack by half. The findings were presented at the 2025 American Heart Association Scientific Sessions in New Orleans.
Vitamin D, often called the ‘sunshine vitamin,’ is essential for bone and immune health, but it also plays an important role in heart health.
Low levels of vitamin D have been linked to a higher risk of heart disease, yet past studies that tested vitamin D supplements didn’t show clear benefits for preventing heart attacks. That led scientists to wonder whether the problem wasn’t the vitamin itself—but rather how it was being given.
In this new trial, known as the TARGET-D study, researchers took a different approach. Instead of giving all patients the same supplement dose, they used a ‘target-to-treat’ method.
This meant that each patient’s blood levels of vitamin D were tested regularly, and their vitamin D3 dosage was adjusted until it reached what researchers considered an optimal level—above 40 nanograms per milliliter (ng/mL).
By personalizing the treatment, the researchers hoped to find out whether reaching this target level, rather than simply taking supplements, could lower the risk of another heart attack.
The study followed 630 patients who had suffered a heart attack within the previous month. Participants were randomly assigned to one of two groups: one received standard care with no vitamin D management, and the other received personalized vitamin D3 treatment. Most of the patients—about 85%—started the study with low vitamin D levels, below 40 ng/mL.
To reach the desired level, many needed higher doses of vitamin D3 than what is usually recommended. Over half of the patients in the targeted treatment group required an initial dose of 5,000 international units (IU) per day, much higher than the standard recommendation of 600 to 800 IU.
Patients in the study had their vitamin D levels checked regularly. Those who reached healthy levels were monitored yearly, while those who remained low were checked every three months and had their doses adjusted as needed.
Researchers then tracked all participants for several years to see who went on to have additional heart-related events such as another heart attack, heart failure, stroke, or death.
In total, 107 of the 630 patients experienced a major cardiac event during the follow-up period. While the overall rate of major events was similar between the two groups, the difference in second heart attacks was dramatic.
Patients who received the personalized vitamin D treatment were about 50% less likely to suffer another heart attack compared to those who did not receive targeted vitamin D management.
Dr. Heidi May, a cardiovascular epidemiologist at Intermountain Health and the study’s lead author, said the results were exciting. “We observed no negative side effects from giving patients higher doses of vitamin D3, and to see such a strong reduction in repeat heart attacks is very encouraging,” she said.
However, she also noted that larger trials are needed to confirm the results and better understand how this approach might prevent other heart problems.
The findings are especially relevant given how common vitamin D deficiency is worldwide. Experts estimate that up to two-thirds of people have low levels of the vitamin, partly because of reduced sun exposure due to lifestyle changes and skin cancer prevention advice.
For these individuals, supplementation may be an important way to restore healthy vitamin D levels and protect long-term heart health.
Reviewing the study, the results suggest that a one-size-fits-all approach may not be the best way to use vitamin D for heart protection. By carefully tracking blood levels and adjusting doses, doctors may be able to help patients achieve optimal vitamin D levels and reduce their risk of another heart attack.
Still, researchers caution that more data is needed before vitamin D testing and high-dose supplementation become routine parts of post-heart-attack care.
If confirmed by larger studies, this simple and low-cost strategy could provide an easy way to help heart attack survivors live longer, healthier lives. For now, the study adds to growing evidence that maintaining good vitamin D levels isn’t just important for bones—it may also be vital for the heart.
If you care about nutrition, please read studies that vitamin D can help reduce inflammation, and vitamin K may lower your heart disease risk by a third.
For more health information, please see recent studies about foods that could sharp your brain, and results showing cooking food in this way may raise your risk of blindness.
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