People with inflammatory bowel disease have vitamin D levels less than half those of healthy people, with nearly 8 out of 10 IBD patients showing severe deficiency. A 2026 cross-sectional study of 594 people found that IBD patients had median vitamin D levels of 18.0 nanomoles per liter compared to 31.0 in controls, and the connection was especially strong in women and those with Crohn disease. While this shows a clear association, researchers cannot yet prove whether low vitamin D causes IBD or results from it.
A new study from 2026 found that people with inflammatory bowel disease (IBD), a condition causing gut inflammation, have much lower vitamin D levels than healthy people. Researchers compared 184 IBD patients with 410 healthy controls and discovered that nearly 8 out of 10 IBD patients had severe vitamin D deficiency. The connection was especially strong in women and in people with Crohn disease, one type of IBD. According to Gram Research analysis, this finding suggests that vitamin D testing and supplementation might be important for IBD patients, though more research is needed to understand exactly how vitamin D affects disease progression.
Key Statistics
A 2026 cross-sectional study of 184 IBD patients and 410 healthy controls found that 78.8% of IBD patients had severe vitamin D deficiency, compared to much lower rates in the control group.
According to research reviewed by Gram, women with severe vitamin D deficiency were 10.57 times more likely to have IBD than women with normal vitamin D levels, while men showed a 4.64-fold increased likelihood.
A 2026 study published in Medicine found that IBD patients had median vitamin D concentrations of 18.0 nanomoles per liter versus 31.0 in healthy controls, a statistically significant difference (P less than 0.001).
Crohn disease patients in a 2026 study had significantly lower vitamin D levels (16.5 nanomoles per liter) compared to ulcerative colitis patients (22.0 nanomoles per liter), suggesting disease-type specific vitamin D patterns.
The Quick Take
- What they studied: Whether people with inflammatory bowel disease have lower vitamin D levels than people without the disease, and if vitamin D deficiency connects to specific patient characteristics.
- Who participated: 184 patients with IBD (122 with Crohn disease and 62 with ulcerative colitis) from a hospital in the Middle East, plus 410 healthy people without IBD used as a comparison group.
- Key finding: IBD patients had vitamin D levels that were less than half those of healthy people (18.0 versus 31.0 nanomoles per liter), and nearly 79% of IBD patients had severe deficiency. Women with IBD showed an especially strong connection to severe vitamin D deficiency.
- What it means for you: If you have IBD, your doctor should check your vitamin D levels. Vitamin D supplementation might be helpful, but talk with your healthcare provider before starting any new supplement, as this study shows an association rather than proving vitamin D deficiency causes IBD.
The Research Details
This was a cross-sectional study, which means researchers looked at two groups of people at one point in time rather than following them over months or years. They measured vitamin D levels in 184 patients with IBD who were being treated at a major hospital and compared those levels to 410 healthy people without IBD. The researchers used blood tests to measure a form of vitamin D called 25-hydroxyvitamin D, which is the standard way doctors check vitamin D status. They then looked at whether vitamin D levels differed based on sex, age, and the type of IBD the patient had (Crohn disease versus ulcerative colitis).
The researchers used statistical tests to determine if the differences they found were real or just due to chance. They also calculated odds ratios, which show how much more likely someone is to have IBD if they have severe vitamin D deficiency compared to someone with normal vitamin D levels. This approach allowed them to see patterns in the data while accounting for other factors that might affect vitamin D levels.
Cross-sectional studies are useful for identifying patterns and connections between health conditions and other factors. In this case, the design allowed researchers to quickly compare vitamin D levels across a large group of IBD patients and controls. However, this type of study cannot prove that low vitamin D causes IBD or that vitamin D deficiency makes IBD worse. It only shows that these two things occur together. Understanding these patterns is important because it can guide doctors to test for vitamin D deficiency in IBD patients and may lead to future studies that test whether vitamin D supplementation helps.
This study has several strengths: it included a reasonable number of participants (594 total), used a standard blood test to measure vitamin D, and compared IBD patients to a control group without IBD. The study was conducted in the Middle East, where vitamin D deficiency is common due to sun exposure patterns and dietary factors, so the findings may be especially relevant for that region. However, the study has limitations. It was conducted at a single hospital, so the results may not apply to all IBD patients everywhere. The researchers did not have information about sun exposure, diet, or vitamin D supplement use, which could have affected the results. Additionally, the study cannot prove cause and effect, only that vitamin D deficiency and IBD occur together.
What the Results Show
The most striking finding was that IBD patients had vitamin D levels that were dramatically lower than healthy controls. The median vitamin D level in IBD patients was 18.0 nanomoles per liter compared to 31.0 in healthy people, a difference that was statistically significant (P less than 0.001, meaning this result would occur by chance less than 1 in 1,000 times). Even more concerning, 78.8% of IBD patients had severe vitamin D deficiency, defined as levels below 25 nanomoles per liter.
The connection between severe vitamin D deficiency and IBD was stronger in women than in men. Women with severe vitamin D deficiency were about 10.5 times more likely to have IBD compared to women with normal vitamin D levels. Men with severe vitamin D deficiency were about 4.6 times more likely to have IBD. This sex difference was statistically significant, suggesting that women may be particularly vulnerable to the effects of vitamin D deficiency in relation to IBD.
When researchers looked at the two main types of IBD separately, they found that Crohn disease patients had even lower vitamin D levels than ulcerative colitis patients (16.5 versus 22.0 nanomoles per liter). This suggests that vitamin D deficiency may be especially pronounced in Crohn disease. However, vitamin D levels did not vary based on specific features of the disease, such as how severe the Crohn disease was or how much of the colon was affected in ulcerative colitis patients.
The study found that vitamin D deficiency was extremely common in this IBD population, affecting nearly 4 out of 5 patients. This high prevalence suggests that vitamin D deficiency may be a systemic issue in IBD rather than affecting only certain subgroups. The fact that vitamin D levels were lower in Crohn disease than ulcerative colitis, even though both are forms of IBD, suggests that different types of gut inflammation may have different relationships with vitamin D. The researchers did not find associations between vitamin D levels and specific disease characteristics like disease severity or extent, which suggests that vitamin D deficiency may be a general feature of having IBD rather than being linked to how severe the disease is.
Previous research has shown that vitamin D deficiency is common in IBD patients worldwide, but most studies have come from Europe and North America. This study adds important data from the Middle East, a region where vitamin D deficiency is particularly common due to factors like limited sun exposure in some populations and dietary patterns. The finding that women show a stronger association between vitamin D deficiency and IBD is relatively novel and suggests that sex-specific factors, such as hormones or differences in immune response, may play a role. The extremely high rate of severe vitamin D deficiency in this population (nearly 79%) is higher than many previous reports, which may reflect regional differences or the specific characteristics of the hospital population studied.
This study has several important limitations that readers should understand. First, it was conducted at a single hospital in the Middle East, so the results may not apply to IBD patients in other regions or countries. Second, the study is cross-sectional, meaning it shows that vitamin D deficiency and IBD occur together but cannot prove that one causes the other. It is possible that having IBD causes vitamin D deficiency, or that some third factor causes both. Third, the researchers did not collect information about sun exposure, dietary vitamin D intake, or whether patients were taking vitamin D supplements, all of which could affect vitamin D levels. Fourth, the control group was from a previously published study rather than being recruited specifically for this research, which could introduce differences in how vitamin D was measured or reported. Finally, the study did not measure other factors that might explain the connection, such as differences in immune function or inflammation markers between groups.
The Bottom Line
If you have IBD, ask your doctor to check your vitamin D level through a blood test. If your level is low, your doctor may recommend vitamin D supplementation, though the appropriate dose should be determined by your healthcare provider based on your individual needs and other medications you take. The evidence for vitamin D supplementation in IBD is still developing, so this recommendation is based on the high prevalence of deficiency and the known importance of vitamin D for immune function, not on proven benefits for IBD outcomes. Moderate confidence: the association between vitamin D deficiency and IBD is clear, but whether supplementation improves outcomes requires further research.
This research is most relevant for people with IBD, particularly those with Crohn disease and women with IBD. Healthcare providers treating IBD patients should consider vitamin D screening as part of routine care. People without IBD do not need to change their behavior based on this study, though maintaining adequate vitamin D levels is important for overall health. People in regions with limited sun exposure or those with dietary restrictions may want to discuss vitamin D status with their doctors regardless of IBD status.
If you start vitamin D supplementation, it typically takes 2 to 3 months to significantly raise blood vitamin D levels. However, this study does not provide information about how quickly vitamin D supplementation might affect IBD symptoms or disease activity. Longer-term studies would be needed to determine whether correcting vitamin D deficiency improves IBD outcomes or reduces flare-ups.
Frequently Asked Questions
Do people with inflammatory bowel disease have lower vitamin D than healthy people?
Yes. A 2026 study found IBD patients had vitamin D levels less than half those of healthy controls (18.0 versus 31.0 nanomoles per liter), with 78.8% of IBD patients showing severe deficiency. The connection was especially strong in women and Crohn disease patients.
Should I take vitamin D supplements if I have Crohn disease or ulcerative colitis?
Ask your doctor to check your vitamin D level first. If you have deficiency, your doctor may recommend supplementation, though the appropriate dose depends on your individual needs and other medications. This study shows deficiency is common but doesn’t yet prove supplementation improves IBD outcomes.
Why do women with IBD have more vitamin D deficiency than men?
This study found women with severe vitamin D deficiency were 10.5 times more likely to have IBD versus 4.6 times for men, but the exact reason is unclear. Sex-specific factors like hormones or immune differences may play a role, but more research is needed.
Does vitamin D deficiency cause inflammatory bowel disease?
This study shows vitamin D deficiency and IBD occur together but cannot prove one causes the other. It’s possible low vitamin D contributes to IBD, or that having IBD leads to low vitamin D, or that another factor causes both. Larger studies are needed to determine causation.
How long does it take to raise vitamin D levels with supplements?
Blood vitamin D levels typically increase within 2 to 3 months of consistent supplementation, though the exact timeline depends on your starting level and supplement dose. Your doctor can monitor progress with blood tests and adjust your dose as needed.
Want to Apply This Research?
- Track your vitamin D supplementation dose and timing daily, and log any changes in IBD symptoms such as abdominal pain, bowel movement frequency, or energy levels. Record your vitamin D blood test results when available to monitor whether supplementation is raising your levels.
- If your doctor recommends vitamin D supplementation, set a daily reminder to take your supplement at the same time each day, such as with breakfast. Log this in your app to build consistency and track adherence over time.
- Schedule vitamin D blood tests every 3 to 6 months if you are supplementing, and track the results in your app. Also monitor IBD symptoms weekly to see if there are any patterns related to vitamin D levels or supplementation. Share this data with your gastroenterologist at your regular appointments to guide treatment decisions.
This research shows an association between vitamin D deficiency and inflammatory bowel disease but does not prove that vitamin D deficiency causes IBD or that supplementation will improve IBD outcomes. If you have IBD or suspect you may have it, consult with a gastroenterologist or healthcare provider for proper diagnosis and treatment. Do not start vitamin D supplementation or change your IBD treatment without discussing it with your doctor first. This article is for informational purposes only and should not replace professional medical advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.