Common vitamin could protect some heart attack survivors, study shows

People with a history of cardiac arrest could protect themselves from future risk with one simple daily habit.

A study at Intermountain Health in Salt Lake City, Utah, discovered that supplementing with vitamin D3 can significantly reduce the risk of a second heart attack in those who have already suffered one.

In a large, randomized clinical trial, researchers monitored patients’ blood levels for vitamin D, while adjusting doses to "achieve optimal levels," according to a press release.

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They found that treating heart attack patients with higher doses of vitamin D3 cut the risk of a second heart attack in half.

The findings were presented at the 2025 American Heart Association Scientific Sessions in New Orleans on Sunday.

The study, called the TARGET-D trial, involved 630 patients between April 2017 and May 2023 who had experienced a heart attack within the previous month. Eighty-five percent had insufficient vitamin D3 levels.

Participants were separated into two groups: One received targeted vitamin D3 treatment, and the other did not. The goal was to raise blood levels to more than 40 nanograms per milliliter (40 ng/mL).

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Participants in the vitamin D treatment group had their blood levels checked once a year to determine whether they were above 40 ng/ml. 

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More than half of them required an initial dose of 5,000 international units (IU). (Most adults are advised to take 600 to 800 IU of vitamin D per day to maintain a level of around 30 to 50 ng/mL.)

The participants were followed until March 2025 to monitor their cardiovascular health. Of the 630 patients, 107 experienced a major cardiac event.

Lead researcher Heidi May, Ph.D., cardiovascular epidemiologist at Intermountain Health, said in a statement that no adverse outcomes were noted after administering higher doses of vitamin D3.

"We’re excited [about] these results, but we know we have further work to do to validate these findings," she said.

Up to two-thirds of people worldwide have low levels of vitamin D, according to May.

Sun exposure is the most common, natural method of getting sufficient amounts of the vitamin, but that has decreased due to lifestyle changes in recent years, according to Intermountain.

Dr. Bradley Serwer, a Maryland-based interventional cardiologist and chief medical officer at VitalSolution, who was not involved in the study, said it’s "long been recognized" that maintaining optimal levels of vitamin D offers "substantial cardiovascular benefits."

"Previous studies have established a correlation between low serum vitamin D levels and an elevated risk of hypertension, coronary artery disease, stroke and heart failure," he told Fox News Digital.

However, the prior research failed to demonstrate how effective vitamin D supplements were in reducing the risk of heart attacks, according to Serwer. 

"Notably, these studies often prescribed a standard replacement dosage that was often insufficient to restore healthy vitamin D levels," he noted.

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These new findings of a 50% risk reduction for second-time heart attacks, although encouraging, involved higher-risk patients and may not apply to lower-risk populations, the cardiologist pointed out.

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"Further research is necessary to assess the efficacy of vitamin D supplementation in lower-risk individuals," he said. "If vitamin D levels are within the normal range, the evidence regarding the benefits of additional supplementation is inconclusive."

Fox News senior medical analyst Dr. Marc Siegel commented in a separate interview with Fox News Digital that this study highlights what is already known about vitamin D and heart health.

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"This is an important study about keeping levels normal," he said. "Vitamin D deficiency leads to inflammation and blood clotting. Normal vitamin D values have been shown to decrease coronary artery disease, heart failure and stroke."

Siegel added that vitamin D is "more of a hormone than a vitamin," which is "crucial to organ function, including the heart."