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Study finds vitamin D3 cuts second heart attack risk in half

A randomized trial found that giving vitamin D3 to individuals who had experienced a heart attack reduced the risk of a second event by half in comparison with participants who received standard care without vitamin D3.

The TARGET-D trial included 630 patients from the Intermountain Health healthcare system in Salt Lake City who had a heart attack within a month of enrollment between April 2017 and May 2023. Researchers compared cardiovascular event risks between 314 participants who were not given vitamin D3 and 316 participants who were given vitamin D3 with a targeted blood level of 40 nanograms per milliliter (ng/mL).

"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," principal investigator Heidi T. May, PhD, MSPH, FAHA, of Intermountain Health explained. "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 40-80 ng/mL."

Among participants who received targeted vitamin D3 treatment, over half required an initial daily dose of 5,000 international units (IU). (The current dose recommended by the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine for adults is 600 to 800 IU.)

Participants were followed until March 2025, during which time 107 major cardiovascular events, including heart attack, heart failure hospitalization, stroke or death occurred. While there was no difference between the groups in the outcome of major adverse cardiovascular events, second heart attack was reduced by half among those who received targeted vitamin D management. "We observed no adverse outcomes when giving patients higher doses of vitamin D3," Dr May noted. "We're excited with these results but know we have further work to do to validate these findings."

The findings were presented November 9, at the 2025 American Heart Association Scientific Sessions.¹

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Apply What You've Learned: Vitamin D

Vitamin D is a hormone that is made in the body and obtained from certain foods. Fatty fish and fish oil, some mushrooms, and fortified milks and cereals are dietary sources. Many individuals choose to add vitamin D capsules, liquid or tablets to their diets.
While vitamin D can be made in the body following exposure to the sun’s ultraviolet (UV) rays, the American Academy of Dermatology (AAD) does not recommend obtaining vitamin D from sun exposure or indoor tanning. According to the AAD, "There is not a safe level of UV exposure from the sun or indoor tanning devices that allows for maximum vitamin D synthesis without increasing skin cancer risk."²
It is estimated that deficient vitamin D blood serum levels of less than 20 ng/mL affect 24% of the U.S. population and that severe vitamin D deficiency of less than 12 ng/mL affects 5.9%.³ Vitamin D insufficiency (20 ng/mL–30 ng/mL) has been estimated to be present in 40.9% of Americans.⁴ Blood vitamin D levels should be regularly evaluated to ascertain whether vitamin D deficiency or insufficiency is present. Serum 25-hydroxyvitamin D is a commonly ordered blood test to assess vitamin D status.
Although anyone can have insufficient or deficient vitamin D levels, an increased risk of deficiency is associated with chronic disease (especially heart, kidney and liver failure), gastrointestinal diseases, hospitalization, hyperparathyroidism or hypoparathyroidism, sarcoidosis, tuberculosis, obesity, osteoporosis, chronic falls, cancer, pregnancy and lactation, respiratory diseases and the use of certain medicines such as glucocorticoids.³

References

2025 American Heart Association Scientific Sessions. New Orleans. 2025 Nov 9.
Vitamin D stats and facts. American Academy of Dermatology Association. https://www.aad.org/media/stats-vitamin-d Accessed 2025 Nov 11.
Amrein K, Scherkl M, Hoffman M, et al. Vitamin D deficiency 2.0: an update on the current status worldwide. Eur J Clin Nutr. 2020 Jan 20;74(11):1498–1513. doi: 10.1038/s41430-020-0558-y
https://pmc.ncbi.nlm.nih.gov/articles/PMC9573946/

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