High-Dose Vitamin D Might Prevent Repeat Heart Attack, Study Finds

A new study has experts cautiously excited about the potential benefits of vitamin D supplementation for people living with heart disease.

Results from a preliminary trial found that heart attack survivors who received personalized doses of vitamin D were more than 50 percent less likely to have a repeat heart attack, compared with people who did not follow this regimen but got standard treatment.

“I think people are opening their minds to the concept that vitamin D might be something that is good for heart health,” says Heidi T. May, PhD, the study’s principal author and an epidemiologist and professor of research at Intermountain Health in Salt Lake City.

“It does need more study, but I think there’s the opportunity to reevaluate vitamin D levels — how we’re actually prescribing it and monitoring it, and that it shouldn’t just be a fixed dose for everyone,” says Dr. May.

Aggressively Optimizing Vitamin D Levels May Help Prevent Heart Attacks

For this randomized trial, researchers set out to study whether or not optimal levels of vitamin D in people with heart disease could help lower their risk of cardiovascular events like heart attack, heart failure, stroke, and death.

To do so, they recruited more than 600 adults with acute coronary syndrome (coronary artery blockage that reduces blood flow to your heart) who were treated at a Utah medical center between 2017 and 2023. A majority of the participants were men (78 percent) with an average age of 63, and nearly half had a previous heart attack.

A majority (more than 85 percent) started the study with vitamin D blood levels below 40 nanograms per milliliter (ng/mL), which is considered insufficient for optimal health.

One group received customized vitamin D supplementation to get them up to recommended levels (in this case, between 40 ng/mL and 80 ng/mL), with the opportunity for dose adjustments every three months. The other group didn’t receive vitamin D monitoring or dose-tailoring.

After following participants for nearly four years on average, the researchers found:

Participants who received personalized vitamin D had a 52 percent lower risk of having a heart attack, compared with participants who didn’t receive vitamin D level management.
While tailored vitamin D supplementation appeared to be beneficial for preventing heart attack specifically, this personalized dosing did not significantly reduce rates of stroke, heart failure hospitalization, or death.

“The large benefit was surprising — almost a halving of event rate is quite remarkable and would need to be repeated in a multicentre study to confirm. But there are plenty of reasons why vitamin D might be especially beneficial in this acute group,” says Klaus Witte, MD, a senior lecturer and consultant cardiologist at the University of Leeds in England who has studied the heart health effects of taking vitamin D supplements.

Research on Vitamin D and Heart Health Has Yielded Conflicting Results in the Past

Though more commonly known for its role in bone development, vitamin D has also been linked to heart health. Exactly how, though, has been unclear.

For example, one recent study found that supplementing with high-dose vitamin D monthly might decrease the risk of having a heart attack or another major cardiac event in older adults. But earlier research suggested vitamin D had no effect on heart attack prevention.

May says this new trial aimed to look at personalized vitamin D dosing based on each participants’ blood test results, rather than standard dosing, to potentially improve patient care.

“As we started thinking about it, all of the previous clinical trials pretty much gave fixed doses of vitamin D, and they didn’t necessarily always test participants’ blood levels or adjust, so we started thinking, well, maybe they’re the reason that they’re not getting positive findings is because they’re not getting participants’ blood levels of vitamin D high enough,” says May.

Though much more evidence is needed, Dr. Witte says the findings add to a growing body of research suggesting personalized vitamin D dosing could be useful for preventing heart attack.

Supplementing With Vitamin D: How Much Is Too Much?

In this trial, roughly half of the participants (52 percent) who received personalized vitamin D dosing required more than 5,000 IU of the supplement every day in order to reach the study’s blood level threshold of 40 ng/mL.

That threshold is actually double what’s recommended (20 ng/mL) by the Food and Nutrition Board at the National Institutes of Health.

“We had found in some of our observational data that 40 ng/mL of vitamin D [in the blood] was our sweet spot, and that’s why we chose that amount,” says May. “But there’s been this debate for a long time: What is the level of vitamin D you need to be above in order to obtain these potential benefits?”

While too much vitamin D can be risky, researchers monitored doses closely and stopped treatment if vitamin D levels increased above 80 ng/mL — and as Witte notes, it would be “incredibly rare” to run into toxicity issues.

“The doses [in the study] are quite high, but my work and that of others suggests that these doses are safe; the body has a good way to balance too much vitamin D, as is the case with vitamin D that you get from the sun. But it can get overwhelmed — so taking such high doses without monitoring is probably not a good idea,” he says.

Potentially Reducing the Risk of Heart Attack With Vitamin D

As May points out, some of the study limitations include the relatively small number of participants and a lack of diversity: Only adults with a heart disease diagnosis were included, and 90 percent of the participants identified as white. Because these factors can limit the applicability of the findings, May suggests future clinical trials include broader populations.

She also emphasizes the importance of discussing vitamin D supplementation with a healthcare provider, rather than taking matters into your own hands.

“Our study shows that vitamin D supplementation is not just a catch-all — it’s very much a personal thing, which is why it’s important to have a dialogue with your healthcare provider about your vitamin D levels and heart health,” she says.