September 8, 2026

(Shutterstock)

Inflammatory bowel disease (IBD) inflames the digestive tract, which makes it harder for the body to absorb nutrients, including vitamin D, a nutrient that helps maintain immune function. People with IBD are often low in vitamin D, and the lowest levels are associated with the worst IBD outcomes. But an association isn’t proof. “Low vitamin D might just be a flag for sicker patients rather than making them sicker,” explained Jared Sninsky, M.D., M.S.C.R., assistant professor of medicine in gastroenterology at Baylor College of Medicine. “The question we wanted to answer was whether correcting it actually changes anything.”

With support from the NCATS Clinical and Translational Science Awards (CTSA) Program, Sninsky and his team investigated this question using 20 years of patient data from the U.S. Department of Veterans Affairs (VA) to find out whether people with IBD who took a vitamin D supplement had better health outcomes. Unlike many treatments, taking a vitamin D supplement is low risk, cheap and easy, and it often has few side effects. The VA real-world data set offered health information collected outside of controlled clinical trials, providing a way to study the benefits of vitamin D supplements over a long period of time, with consistent data collection and in a national group. As part of the National Institutes of Health’s unified strategy, prioritizing the access and use of real-world data and platforms can help accelerate treatment development.

Michael Kurilla, M.D., Ph.D., director of NCATS’ Division of Clinical Innovation, which administers the CTSA Program, commented on the value of the VA data set, stating, “In most people’s minds — including clinicians’ — vitamin D is confined to bone health. But we know that the true picture is more nuanced. The availability of large data sets, such as with the VA, allows for research investigations that would otherwise be difficult to undertake through a traditional, large-scale clinical trial lasting for years.”

This study used three different methods to mimic randomized controlled trials, which are often considered the best way to study diseases and conditions, using real-world data that already had been collected. “Conducting these trials with actual patients would be expensive and require a lot of coordination” Sninsky explained. Instead, the researchers analyzed only existing data and published the results recently in Clinical Gastroenterology and Hepatology.

The study compared changes in clinical outcomes before and after vitamin D testing in people with IBD who did and did not receive supplements. More than 5,000 patients in the data set met the criteria to be included in the study. The researchers found that patients taking vitamin D had decreases in emergency room visits, steroid prescriptions and hospitalizations specific to IBD — events that are common for people with IBD. This finding suggests that taking this easily available supplement reduces the risk of such events and is an effective complement to more complex treatments for IBD.

“This study is important because it’s one of the most powerful and largest retrospective studies to suggest that there is an effect of this intervention,” Sninsky said. The VA data set used for this study contained real-world data from veterans, who tend to be older, with more males than females. These limits are important to consider when applying these results to all people with IBD, so more research is needed for confirmation. However, treatment guidelines already recommend that patients with IBD be screened for vitamin D deficiency. This study can encourage doctors to follow those guidelines and prescribe vitamin D supplements when needed.

“As a translational scientist, I think it’s very important for us to keep in mind how we can leverage clinical data to guide clinicians in taking better care of our patients,” Sninsky commented. “I think that connection between clinical research, basic science and applying it to the bedside is one of the most important things we can do in research.”