New Data Suggests Previous Vitamin D Supplementation Trials May Have Missed the Mark


Viet Le, DMSc, PA-C, discusses early data from the Target-D trial and how this might influence the way he interprets the findings from other vitamin D supplementation studies.

New data from the American Heart Association Scientific Sessions 2023 suggests clinicians and researchers may need to rethink the results of past trials examining the use of vitamin D for reducing risk of cardiovascular events.

An analysis of data from participants in the TARGET-D trial, results indicate, despite supplementation, more than half of the patients in the trial failed to achieve serum vitamin D levels of more than 40 ng/mL, which leads investigators to suggest contemporary vitamin D studies may have been underdosing participants.

“We’ve seen a series of studies that report an association between low Vitamin D and poor heart outcomes, but also a few randomized clinical trials that do not report the same association,” said lead author, Heidi May, PhD, an epidemiologist at Intermountain Health. “Our findings here show that just giving patients some Vitamin D does not help them achieve optimal levels. If researchers are going to further look at Vitamin D dosing as a possible way to improve heart health, patients need to be given the right doses to reach those ideal levels.”

A randomized clinical trial, Target-D was launched with the intent of exploring whether achieving an ideal Vitamin D level through personalized management of Vitamin D supplementation will result in the reduction of cardiovascular-related outcomes. Per trial protocol, patients with a baseline serum vitamin D greater than 40 ng/mL received no supplementation and would return at 12-months for reassessment. In contrast, those with a baseline serum serum vitamin D less than 40 ng/mL received uptitrated vitamin D supplementation and returned in 3-month intervals for assessment and dosing adjustment, until levels were greater than 40 ng/mL.

Of the 632 patients included in the study, 316 were randomized to vitamin D supplementation. These 316 participants had a mean age of 62.8 (Standard Deviation [SD], 11.3) years, 23.1% were female, and 90% white. Overall, the mean serum vitamin D levels was 25.9 (SD, 11.5) ng/mL, the median level was 24 ng/mL, and 89.4% required vitamin D3 dosing.

Upon analysis, results indicated just 13.5% of participants were able to achieve the threshold of 40 ng/mL using 2,000 international units (IU) daily, 20.8% needed 3000-4000 IU, 51% needed 5000-8000 IU, and 14.6% required 10,000 IU or more.

“These findings show that without taking a tailored approach to evaluating and dosing with Vitamin D, patients most likely will not see any results,” added Viet T. Le, DMSc, PA-C, researcher and physician associate at Intermountain Health. “We need to be far more intentional in how we’re treating patients with Vitamin D beyond just telling them to take a vitamin pill.”

With an interest in learning more about this study, our editorial team sat down with Le during on-site coverage of AHA 2023.

Le has no relevant disclosures to report.


  1. Le V, Babcock D, Wayman L, et al. Higher Than Daily RDA Recommended Vitamin D3 Dosing and Multiple Titrations Are Required to Achieve >40 ng/mL 25-hydroxy Vitamin D Levels in Acute Coronary Syndrome (ACS) Participants Enrolled and Randomized to Targeted Vitamin D Treatment: The Target D Trial. Paper presented at: American Heart Association Scientific Sessions 2023; November 10 - 13; Philadelphia, PA. Accessed November 10, 2023.
  2. Gomez J. New Study finds current dosing recommendations may not help patients achieve optimal vitamin D levels: Intermountain Healthcare. November 12, 1970. Accessed November 14, 2023.
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