Copyright Medical News Today
A new study from researchers with Intermountain Health in Salt Lake City examined the effect of vitamin D3 supplementation on people who previously had heart attacks. The researchers did not give everyone the same vitamin D3 dosage but instead adjusted the amount based on the needs of each participant. The researchers found that vitamin D3 may drastically reduced the risk of having a second heart attack. Vitamin D is important for maintaining health and supports bone health, influences the immune system, and supports muscle and nerve functioning. Researchers are taking a closer look at how vitamin D can impact heart health. While prior observational studies found low levels are associated with poor cardiovascular health, trial results were mixed. Intermountain Health researchers have now conducted a new trial on people who already had a heart attack. They monitored the participants’ vitamin D blood levels and adjusted their doses to maintain optimal levels throughout the trial. The treatment cut the risk of a repeat heart attack in half compared to those who did not receive the supplementation. The study was being presented at the American Heart Association Scientific Sessions 2025, and its results are not yet published in a peer-reviewed journal. According to the Food and Nutrition Board, adults ages 18 to 70 should take in 600 International Units (IU) of vitamin D per day. People can get vitamin D3 by spending time in the sun, and it is also available in supplements and foods such as fortified cereals and milk and occurs naturally in fatty fish (salmon, tuna, and mackerel). Vitamin D deficiency can occur due to limited exposure to sunlight, poor diet, or medical conditions. Doctors can detect this through a blood test and may prescribe taking a high vitamin D3 dose. Researchers have become increasingly interested in vitamin D3’s potential heart benefits. The scientists who conducted the current study focused on whether targeted vitamin D3 treatment might help people who have had a heart attack. The researchers noted that prior clinical trial results were inconsistent but thought that could be related to administering the same dose of vitamin D3 to all participants. They decided to try adjusting the amount of vitamin D3 supplementation based on individual needs rather than using a one-size-fits-all approach. The average age of participants in the TARGET-D trial was 63, and most of the 630 participants were males. They enrolled within a month of having a heart attack. The researchers randomly selected the control group and who would receive the targeted vitamin D3 treatment. At the time of enrollment, 87% of participants had low vitamin D levels. The target level was 40 nanograms/milliliter (ng/ml), and the average vitamin D level was 27 ng/ml. The researchers administered a high vitamin D3 starting dose of 5,000 UI to nearly 60% of participants. The researchers monitored vitamin D3 levels throughout the trial to make sure they remained at the target level. If someone’s vitamin D level dropped below that, they received vitamin D supplementation to get back on track. The researchers kept track of major cardiovascular events throughout the trial, including death, heart attack, hospitalization for heart failure, and stroke. While there was no significant difference between groups in overall cardiac events, the targeted vitamin D3 treatment group had half as many follow-up heart attacks as the control group. The rate of follow-up heart attacks was 3.8% in the test group compared to 7.9% in the control group. Overall, while the results suggest that targeted vitamin D3 supplementation may not reduce all major cardiac outcomes, it did cut the risk of repeat heart attacks by more than half. The research team plans to conduct a larger clinical trial to confirm these findings. Cheng-Han Chen, MD, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center, shared his perspective on the trial with Medical News Today. Chen, who was not involved in this study, explained that while past research has linked higher blood levels of vitamin D with lower heart disease rates, “it mostly appears that the relationship between vitamin D3 and heart health is that of correlation rather than that of causation.” He noted that vitamin D3 may still offer some cardiovascular benefits, such as “decreasing inflammation and lowering blood pressure.” However, he cautioned that the evidence remains mixed. He added that if larger studies confirm the recent finding that targeted vitamin D3 treatment could reduce the risk of recurrent heart attacks, “it would be quite significant.” Louis Malinow, MD, Director of Education and Clinical Excellence at MDVIP and Diplomate of the American Board of Clinical Lipidology, also spoke with MNT about the trial. “I commend the authors for finally being the first to aim at a specific level of vitamin D in this trial,” said Malinow, who likewise was not involved in the research. “So many vitamin D trials have failed to show any benefit as patients were broadly prescribed the same dose and levels were not checked.” “It may lower blood pressure and reduce inflammation, both of which have a role in heart disease.”
