Could Personalized Vitamin D Help Prevent Another Heart Attack?

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Results of a new preliminary study suggest that people with heart disease who have already experienced a heart attack may lower their risk of having another one by optimizing their vitamin D levels. In this research, presented at the American Heart Association’s Scientific Sessions 2025, adults with a history of heart disease were given vitamin D in personalized doses based on blood test results, rather than a standard one-size-fits-all amount.

At the beginning of the TARGET-D study, more than 85% of participants had low vitamin D levels (below 40 nanograms per milliliter, or ng/mL). Investigators believe levels between 40 and 80 ng/mL may be more supportive of heart health. To reach that range, many people needed much higher doses than the current FDA-recommended 800 International Units (IU) per day. In fact, about half of the participants in the treatment group needed more than 5,000 IU daily — more than six times the standard recommendation — in order to reach their target levels.

“Previous clinical trial research on vitamin D tested the potential impact of the same vitamin D dose for all participants without checking their blood levels first,” explained Heidi T. May, Ph.D., M.S.P.H., FAHA, lead investigator and an epidemiologist and professor of research at Intermountain Health in Salt Lake City, Utah. “We took a different approach. We checked each participant's vitamin D levels at enrollment and throughout the study, and we adjusted their dose as needed to bring and maintain them in a range of 40 to 80 ng/mL.”

The study enrolled 630 people with acute coronary syndrome from Intermountain Medical Center in Utah. The average age of patients was 63 years, most (78%) were men, and nearly half had had a previous heart attack. Participants were placed in either the vitamin D supplementation group or the standard care group. Those in the treatment group received ongoing dose adjustments every three months to reach and maintain optimal vitamin D levels.

Over a follow-up period of about four years, 107 major cardiac events occurred (15.7% in the treatment group and 18.4% in the standard care group). The people who received personalized vitamin D dosing had a 52% lower risk of having another heart attack compared with those whose vitamin D levels were not monitored or adjusted.

However, the study did not find the same strong benefit for other outcomes, such as stroke, heart failure hospitalization or overall death rates. This means vitamin D may be particularly helpful in lowering the risk of heart attacks but not necessarily other heart-related complications.

Safety was also a key focus. Researchers regularly monitored calcium levels and reduced or stopped vitamin D if levels became too high, since excessive vitamin D can lead to serious problems, including kidney damage and abnormal heart rhythms.

It’s important to note that this study is still in its early stages and has not yet been published in a peer-reviewed journal. It was presented as a research abstract, meaning the results are considered preliminary until further analysis is completed. In addition, most participants were White men, so more diverse studies are needed to understand how this approach works in other populations.

Experts stress that no one should start or change vitamin D supplements without talking to their cardiologist first, especially if they have heart disease or other chronic conditions. While the findings are promising, more clinical trials are needed before vitamin D optimization becomes a standard part of heart attack prevention.

Still, the study highlights an important message: Simple factors like vitamin levels — when carefully monitored — may play a meaningful role in heart health.

“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,” concluded May.