Vitamin D Tracks Disease Activity in Inflammatory Bowel Disease

What the Researchers Tested

Researchers at the Medical University of Lodz evaluated serum 25-hydroxyvitamin D (25[OH]D) as an objective marker of inflammatory bowel disease (IBD) activity.

The cross-sectional investigation compared 129 adults diagnosed with IBD against 102 healthy control participants.

The journal published the findings in September 2026.

Blood Levels Across Active Flares and Remission

Patients experiencing an active inflammatory bowel disease flare showed lower circulating vitamin D compared to patients in remission.

Average concentrations measured 22.3 ng/mL during flares and 28.9 ng/mL during remission.

Healthy controls averaged 28.8 ng/mL.

• IBD patients in remission: 28.9 ± 7.2 ng/mL
• IBD patients with active disease: 22.3 ± 6.1 ng/mL
• Healthy control group: 28.8 ng/mL

Disease Subtypes and Dietary Correlations

The drop appeared in both ulcerative colitis and Crohn disease.

In each condition, higher blood levels tracked with clinical remission.

Dietary Intake and Serum Concentrations

Higher serum 25(OH)D concentrations correlated directly with specific nutritional habits in patients with inflammatory bowel disease.

A multivariate regression spline model showed that supplementation and eating fish once per week matched higher blood levels.

Dietary intake alone did not eliminate flares.

Observational Limits and Reverse Causation

Cross-sectional data cannot establish whether low vitamin D causes intestinal inflammation or results from it.

Inflamed tissue absorbs fewer nutrients.

Because of that absorption issue, low blood levels may simply follow the inflammation.

Practical Implications for Lab Monitoring

Clinicians can use routine 25(OH)D blood tests as a noninvasive check alongside established inflammatory markers.

The test is widely available.

Patients managing Crohn disease or ulcerative colitis can discuss regular 25(OH)D monitoring with their care team.