People with inflammatory bowel disease (IBD) often struggle to absorb vitamin D from regular supplements because their digestive systems don’t work normally. Researchers tested a new type of vitamin D supplement that dissolves under the tongue instead of being swallowed. In a study of 120 patients, both the new under-the-tongue method and traditional swallowed supplements raised vitamin D levels similarly over 12-16 weeks. However, the under-the-tongue version worked with a lower dose, suggesting it might be absorbed more efficiently. This finding could help doctors give better vitamin D treatment to people with Crohn’s disease and ulcerative colitis.

The Quick Take

  • What they studied: Whether a new vitamin D supplement that dissolves under your tongue works better than regular swallowed vitamin D pills for people with inflammatory bowel disease.
  • Who participated: 120 adults with inflammatory bowel disease (75 with Crohn’s disease and 45 with ulcerative colitis). About 27% had active disease symptoms at the time of the study, and some had previous bowel surgery.
  • Key finding: Both types of vitamin D supplements raised blood vitamin D levels by similar amounts over 12-16 weeks. However, the under-the-tongue version achieved the same results with half the dose (1,143 IU daily versus 2,000 IU daily), suggesting it may be absorbed more efficiently.
  • What it means for you: If you have inflammatory bowel disease and take vitamin D supplements, an under-the-tongue version might work better with a smaller dose. However, talk to your doctor before switching supplements, as this is one study and more research is needed to confirm these findings.

The Research Details

This was a randomized controlled trial, which is one of the strongest types of medical research. Researchers randomly divided 120 patients into two groups: one group received vitamin D as an oil-based liquid that dissolves under the tongue (2,000 IU weekly), while the other group took traditional swallowed vitamin D pills (4,000 IU twice weekly). Both groups received their supplements during winter months when vitamin D levels naturally drop. Researchers measured vitamin D levels in the blood at the start and after 12-16 weeks of supplementation.

The study included patients with two types of inflammatory bowel disease: Crohn’s disease and ulcerative colitis. Some patients had active disease symptoms, while others had their disease under control. A portion of Crohn’s disease patients had undergone surgery to remove part of their intestines, which can affect nutrient absorption.

This design allowed researchers to directly compare whether the new under-the-tongue method worked differently than traditional supplements in people whose digestive systems don’t absorb nutrients normally.

People with inflammatory bowel disease have damaged intestines that don’t absorb nutrients well, including vitamin D. Regular vitamin D supplements may not work effectively because they rely on normal intestinal absorption. Testing an under-the-tongue method matters because it bypasses the damaged intestines and delivers vitamin D directly through mouth tissues. Understanding which delivery method works best helps doctors treat vitamin D deficiency more effectively in this vulnerable population.

This study has several strengths: it was randomized (reducing bias), included a reasonable sample size (120 patients), and measured actual blood vitamin D levels rather than relying on patient reports. However, the study was open-label, meaning both patients and researchers knew which treatment each person received, which could introduce some bias. The study was conducted during winter months only, so results may not apply to other seasons. The study lasted 12-16 weeks, which is a reasonable timeframe but relatively short for evaluating long-term supplement effectiveness.

What the Results Show

Both vitamin D supplements increased blood vitamin D levels by approximately 9 nmol/L over the study period. This increase was nearly identical between groups (9.3 nmol/L for the under-the-tongue version versus 9.2 nmol/L for the swallowed version), and the variation between individual patients was similar in both groups.

The proportion of patients who reached normal vitamin D levels after supplementation was comparable between the two groups. This means that both methods were equally effective at bringing vitamin D levels into the healthy range.

Importantly, the under-the-tongue version achieved these results with half the dose of the traditional supplement. This suggests the mouth-based delivery method may be absorbed more efficiently by the body. The researchers calculated that the under-the-tongue version needed only 1,143 IU daily to match the effect of 2,000 IU daily from the traditional supplement.

The researchers looked at whether other factors explained why some people’s vitamin D levels increased more than others. They found that the only factor that mattered was a person’s starting vitamin D level—people who started with lower vitamin D levels tended to have bigger increases. This was true for both groups. Surprisingly, factors like whether someone had active disease, whether they’d had bowel surgery, or other health conditions didn’t significantly affect how much their vitamin D levels increased.

Previous research suggested that people with inflammatory bowel disease might absorb vitamin D poorly because of their damaged intestines. This study challenges that assumption somewhat by showing that traditional oral vitamin D supplements do work in this population, though perhaps not as efficiently as the new under-the-tongue method. The finding that the under-the-tongue version requires a lower dose aligns with the theory that bypassing the damaged intestines improves absorption. However, the similar overall effectiveness suggests that even damaged intestines can absorb some vitamin D from traditional supplements.

The study only lasted 12-16 weeks during winter months, so we don’t know if results would be the same in other seasons or over longer periods. The study was open-label, meaning patients and doctors knew which treatment each person received, which could influence results through placebo effects or different levels of adherence. The study didn’t measure whether patients actually took their supplements as directed. The initial vitamin D levels were quite low in both groups (below 75 nmol/L is considered deficient), so results may not apply to people with higher starting vitamin D levels. Finally, the study was relatively small, so larger studies would help confirm these findings.

The Bottom Line

Based on this research, the under-the-tongue vitamin D supplement appears to work as well as traditional supplements at half the dose in people with inflammatory bowel disease. However, this is one study, and more research is needed. If you have inflammatory bowel disease and take vitamin D supplements, discuss with your doctor whether switching to an under-the-tongue version might benefit you. Don’t change your supplement routine without medical guidance, as individual needs vary. Confidence level: Moderate—this is solid research but needs confirmation from larger studies.

This research is most relevant for people with Crohn’s disease or ulcerative colitis who take vitamin D supplements or have low vitamin D levels. It may also interest gastroenterologists and other doctors who treat inflammatory bowel disease. People without inflammatory bowel disease should not assume these results apply to them, as their intestines absorb nutrients normally. People with other digestive conditions that affect nutrient absorption might benefit from discussing this research with their doctors.

In this study, vitamin D levels increased over 12-16 weeks. However, the increases were relatively modest (about 9 nmol/L). Most people would need to continue supplementation for several months to see meaningful improvements in vitamin D status. You shouldn’t expect to feel dramatically different after a few weeks—vitamin D works gradually to support bone health, immune function, and other body processes over time.

Want to Apply This Research?

  • If using a health app, track your vitamin D supplement type (under-the-tongue versus swallowed), dose, and frequency. Record any gastrointestinal symptoms on supplementation days to monitor tolerability. Set a reminder to check vitamin D blood levels every 3-6 months with your doctor to see if your chosen supplement method is working.
  • If your doctor recommends switching to an under-the-tongue vitamin D supplement, use your app to set daily reminders at the same time each day. Log when you take the supplement and note any changes in energy, mood, or bone/muscle symptoms. Compare your adherence between the old and new supplement types to see which method you’re more likely to remember to take consistently.
  • Create a long-term tracking system in your app that records vitamin D blood test results over time (every 3-6 months). Track which supplement type and dose you’re using during each testing period. Note seasonal changes in vitamin D levels and adjust supplementation accordingly. Share this data with your doctor to optimize your vitamin D management strategy.

This research summary is for educational purposes only and should not replace professional medical advice. The findings are based on one clinical trial and should not be used to make treatment decisions without consulting your healthcare provider. If you have inflammatory bowel disease or vitamin D deficiency, work with your doctor to determine the best supplementation approach for your individual situation. Do not start, stop, or change any supplements without medical guidance. This summary does not constitute medical advice, diagnosis, or treatment recommendations.