Does Crohn's Disease Cause Vitamin D Deficiency?

January 2, 2026 •

4 min read

According to the Crohn's & Colitis Foundation, malnutrition is common in inflammatory bowel disease, with studies indicating it affects 20–85% of people with IBD. A frequently observed nutrient shortfall, a key complication, is vitamin D deficiency, raising the question: does Crohn's disease cause vitamin D deficiency?

Quick Summary

Crohn's disease frequently leads to vitamin D deficiency due to intestinal inflammation, malabsorption, and reduced sun exposure. Low vitamin D is also linked to increased disease activity and risk of complications, highlighting its importance for immune regulation.

Key Points

Malabsorption: Chronic inflammation from Crohn's can damage the small intestine, especially the ileum, preventing effective absorption of fat-soluble vitamins like vitamin D.
Inflammatory Link: Low vitamin D levels are associated with higher disease activity in Crohn's, suggesting a link where inflammation depletes vitamin D, which in turn plays a role in immune dysregulation.
Dietary Factors: Reduced appetite, food avoidance due to symptoms, and subsequent decreased intake of fortified foods contribute to deficiency.
Surgical Impact: The surgical removal of sections of the small intestine can significantly worsen malabsorption and the risk of vitamin D deficiency.
Monitoring is Key: Regular screening of vitamin D levels is recommended for all Crohn's patients to detect and address deficiencies proactively, with testing particularly important during active disease flares.
Supplementation is Crucial: Higher-dose vitamin D3 supplementation is often necessary for patients with Crohn's to correct and maintain adequate levels, especially during periods of malabsorption.

The Connection Between Crohn's Disease and Vitamin D Deficiency

Crohn's disease, a type of inflammatory bowel disease (IBD), is a chronic condition causing inflammation in the gastrointestinal (GI) tract. This inflammation can occur anywhere from the mouth to the anus, but most commonly affects the small intestine, specifically the ileum. It is well-established that patients with Crohn's are at a higher risk of developing nutritional deficiencies, including a lack of vitamin D, compared to the general population. The link is complex, involving several factors related to the disease itself and its management. Understanding these mechanisms is crucial for effective treatment and supplementation strategies.

How Inflammation Impairs Vitamin D Absorption

The core mechanism driving vitamin D deficiency in Crohn's disease is intestinal malabsorption. Vitamin D is a fat-soluble vitamin, meaning it requires dietary fat for proper absorption. The severe inflammation associated with Crohn's disease can damage the lining of the small intestine, which is the primary site for nutrient absorption. In particular, if inflammation affects the terminal ileum—the section where bile salts are reabsorbed to aid in fat digestion—it can lead to malabsorption of fats and, consequently, fat-soluble vitamins like D, E, A, and K.

Chronic Inflammation and the Immune System Link

Beyond physical malabsorption, the inflammatory nature of Crohn's disease plays a direct role in depleting vitamin D. The ongoing systemic inflammation associated with active disease can lower serum 25-hydroxyvitamin D [25(OH)D] concentrations. Some research suggests this is because the body actively uses up vitamin D during periods of high inflammation. Vitamin D is a potent immunomodulator and plays a crucial role in regulating the immune system. In Crohn's, this process involves shifting the immune response away from a pro-inflammatory state. However, during an inflammatory flare, this process can increase the metabolic clearance of vitamin D, further reducing levels. This creates a cyclical problem: inflammation leads to low vitamin D, which may worsen the dysregulated immune response characteristic of IBD.

Dietary Factors and Reduced Sunlight Exposure

Patients with Crohn's disease often experience symptoms such as abdominal pain, nausea, and diarrhea, which can lead to a reduced appetite and intentional dietary restrictions. This can result in a lower intake of vitamin D from food sources. Furthermore, many individuals with IBD may avoid sun exposure due to feeling unwell or having photosensitive skin reactions from certain medications, limiting the body's natural synthesis of vitamin D from sunlight. Smoking, a known risk factor for Crohn's disease, has also been shown to correlate with lower vitamin D levels.

Medical and Surgical Influences

Medications used to treat Crohn's disease can sometimes contribute to vitamin D deficiency. Corticosteroids, for example, can make the body resistant to vitamin D and interfere with its metabolism, impacting bone health. Surgical removal of parts of the intestine, particularly the terminal ileum, is a significant risk factor for malabsorption and nutrient deficiencies. While surgery can be a necessary part of managing the disease, it can exacerbate the problem of nutrient uptake.

The Importance of Monitoring and Supplementation

Because of these multi-faceted risks, monitoring vitamin D levels in Crohn's patients is essential. Regular blood tests are recommended, especially for those with active disease or those who have had intestinal surgery. Supplementation with vitamin D3 (cholecalciferol) is often necessary to correct deficiencies. Higher doses may be needed to achieve and maintain adequate levels, as the standard dietary recommendations are often insufficient for patients with malabsorption. Your healthcare provider can determine the appropriate dosage and form of supplementation.

Comparison of Factors Contributing to Vitamin D Deficiency


Factor	How It Affects Vitamin D Status in Crohn's	General Population Comparison
Intestinal Malabsorption	Severe inflammation in the small intestine, especially the ileum, impairs the absorption of fat-soluble vitamins.	Typically not a concern unless other GI conditions like celiac disease or cystic fibrosis are present.
Chronic Inflammation	Ongoing systemic inflammation can increase the metabolic clearance and consumption of vitamin D.	Inflammation can affect vitamin D status, but it is not typically as severe or chronic as in IBD.
Reduced Appetite/Diet	Pain, nausea, and dietary restrictions lead to lower intake of vitamin D-rich foods.	Diet is a primary source of vitamin D, but intake may not be affected by digestive symptoms.
Medications	Corticosteroids can cause vitamin D resistance and affect metabolism.	Only a factor for individuals on specific medications that interfere with vitamin D metabolism.
Reduced Sun Exposure	Patients who feel unwell may stay indoors more, limiting natural vitamin D synthesis.	Lifestyle and geographic location are the main determinants of sun exposure.
Bowel Resection	Surgical removal of the ileum critically reduces the surface area available for absorption.	Not a factor unless intestinal surgery has been performed.

Conclusion

In conclusion, there is a strong and well-documented link between Crohn's disease and vitamin D deficiency. The chronic inflammation, intestinal malabsorption, dietary limitations, and potential surgical interventions all contribute to low vitamin D levels. Evidence suggests that low vitamin D levels may also correlate with more active disease and increase the risk of complications, underscoring its crucial role as an immunomodulator. Regular monitoring and targeted supplementation, often with higher doses of vitamin D3, are vital parts of managing Crohn's disease and improving a patient's overall health and quality of life. Patients should always consult with their healthcare team to develop an appropriate and personalized supplementation plan. For more detailed information on nutrient deficiencies, the Crohn's & Colitis Foundation offers comprehensive resources on managing diet and nutrition with IBD.

Frequently Asked Questions

The primary reason is intestinal malabsorption. Inflammation caused by Crohn's disease damages the lining of the small intestine, the main site of vitamin D absorption. Since vitamin D is fat-soluble, inflammation in the ileum also impairs the absorption of the fats needed to carry it.

Research suggests a link between low vitamin D and higher disease activity. Some studies have shown that supplementation can improve disease activity scores and quality of life in patients. However, more large-scale research is needed to determine the full therapeutic benefits.

While vitamin D deficiency is very common in Crohn's patients, it does not affect everyone. The risk is influenced by factors such as the location of the inflammation, disease severity, dietary habits, and medication use.

Most evidence supports the use of vitamin D3 (cholecalciferol) supplements. Given the malabsorption issues, higher doses are often needed compared to the general population to achieve adequate blood levels, and your doctor may recommend intramuscular injections in severe cases.

Experts recommend that patients with inflammatory bowel disease, including Crohn's, have their blood vitamin D levels checked at least once per year, particularly during the winter.

Yes. Corticosteroids, a common treatment for Crohn's flares, can reduce vitamin D's effectiveness and interfere with calcium absorption, further contributing to deficiency and risking bone health.

Some studies have shown that normalizing vitamin D levels in Crohn's patients can be associated with a reduced risk of disease relapse and hospitalizations. It is an important part of overall disease management.