If you’ve already survived one heart attack, the idea that a simple vitamin supplement could cut your risk of another in half sounds almost too good to be true. But that’s precisely what a new study out of Salt Lake City suggests — provided the dose fits your body’s needs.
The Intermountain Health breakthrough
Researchers at Intermountain Health presented findings at the American Heart Association Scientific Sessions 2025 showing that individualized dosing of vitamin D3 — adjusted to maintain optimal blood levels — dramatically lowered the risk of a second heart attack among patients who had already experienced one.
The TARGET-D trial enrolled 630 adults, with an average age of 63, within a month of a heart attack. Roughly 87 percent started the trial with low vitamin D levels (around 27 ng/mL, well below the 40 ng/mL target). Instead of assigning everyone the same dose, clinicians monitored each person’s vitamin D3 levels and adjusted the dose accordingly. More than half of the participants needed a 5,000-IU starting dose to reach and maintain the target.
By the end of the monitoring period, the group receiving targeted vitamin D3 supplementation had half as many follow-up heart attacks as the control group — 3.8 percent versus 7.9 percent.
While overall rates of death, stroke, and heart failure hospitalizations were similar between groups, this reduction in repeat heart attacks stands out. Researchers now plan a larger trial to confirm the results.
Why personalization matters
For years, vitamin D’s role in heart health has been debated. Low vitamin D status has been linked to high blood pressure, inflammation, and poor cardiovascular outcomes, yet prior clinical trials often showed little or no benefit from supplementation.
The difference? Those earlier studies tended to give everyone the same standard dose and rarely checked if blood levels ever improved. The Intermountain team instead tailored dosing — a precision approach that may finally explain why earlier one-size-fits-all trials disappointed.
The vitamin D3 basics
According to the U.S. Food and Nutrition Board, adults aged 18–70 should aim for around 600 IU of vitamin D per day. The body naturally makes vitamin D3 when skin is exposed to sunlight. Still, deficiency is common — especially in people who live at northern latitudes, spend much of their day indoors, or have darker skin.
Vitamin D3 is also found in fortified milk and cereals, as well as in fatty fish like salmon, tuna, and mackerel. Doctors can check blood levels with a simple test and, if low, recommend a customized supplement plan.
What this means for heart patients
This new evidence doesn’t mean everyone should start taking high-dose vitamin D3. The results are preliminary, and the study has not yet been published in a peer-reviewed journal. Still, it raises a key question for anyone with a history of heart disease:
Have your vitamin D levels been checked recently?
If low, would targeted supplementation help maintain a healthy cardiovascular profile?
As a nutritional biochemist, I see this study as a strong case for personalized nutrition. When nutrients are optimized for each individual — rather than prescribed generically — we may finally uncover their true therapeutic potential.
The bottom line
Vitamin D3 supports bone, immune, and muscle health — and now may have a promising role in protecting the heart after an attack. While we await larger trials, this research underscores a simple principle: personalized care often outperforms the “average dose.”
Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult your physician or qualified healthcare provider before starting or changing any supplement or medication, especially if you have heart disease or other medical conditions.
