Especially if you’ve already had one?
I’m going to be straight with you: when I first saw the headline coming out of the American Heart Association’s Scientific Sessions in New Orleans (November 2025), I did a double-take.
A preliminary study just presented at the meeting found that adults with heart disease who had already survived one heart attack and then got their vitamin D levels into an “optimal” range (above 40 ng/mL and kept under 80 ng/mL) with personalized, monitored dosing had 52% fewer repeat heart attacks over the next four years compared to people whose vitamin D levels were never checked or adjusted.
Yes, you read that right — more than half the risk was gone just for heart attacks specifically.
What actually happened in the study? (The TARGET-D trial)
- 630 adults who had already had a heart attack (average age 63)
- Randomly split into two groups
- One group: usual care — no vitamin D testing or special dosing
- Treatment group: regular blood tests + dose adjusted every 3 months until their level stayed solidly between 40–80 ng/mL
- Follow-up: ~4 years
Result → 52% lower risk of another heart attack in the personalized-dosing group.
(The study didn’t see a big drop in deaths, strokes, or heart-failure hospitalizations — the benefit was specific to preventing new heart attacks.)
How common was vitamin D deficiency in these patients?
Extremely common:
- 85% started with levels below 40 ng/mL (many experts now call anything under 40 insufficient for heart patients)
- Nearly 52% of the treatment group needed more than 5,000 IU per day — sometimes a lot more — to reach the target
- That’s over 6× the official U.S. recommended daily amount (600–800 IU)
So should you run out and take 5,000 IU tomorrow?
No — please don’t do that blindly.
Lead researcher Heidi May, PhD (Intermountain Health, Utah) was very clear:
“We encourage people with heart disease to discuss vitamin D blood testing and targeted dosing with their health care professionals to meet their individual needs.”
Taking high doses without checking blood levels (and calcium levels) can be risky. In the study they watched calcium like hawks and lowered or stopped the dose if anyone went over 80 ng/mL.
What should you actually do right now?
- If you have heart disease (especially post-heart-attack), ask your cardiologist or primary-care doctor to check your 25-hydroxyvitamin D level at your next visit. It’s a simple blood test.
- If it’s low, a tailored, monitored plan — not just the 800 IU in a multivitamin — might be worth considering.
- Wait for the full peer-reviewed paper and larger trials before we call this settled science, but this is one of the strongest signals yet that fixing vitamin D the right way could matter a lot for secondary prevention.
I’ll be keeping a close eye on this one. When the full manuscript drops, I’ll update you.
In the meantime, a little sunshine, a smart conversation with your doctor, and one blood test might be one of the easiest things you can do that could — potentially — move the needle in a very big way.
Source: American Heart Association Scientific Sessions 2025 — TARGET-D trial (abstract presentation, preliminary results). Full news release here.
