Researchers at the University of North Carolina discovered that oxalate, a natural compound found in healthy foods like spinach and almonds, may worsen intestinal inflammation in inflammatory bowel disease patients due to impaired gut transporter proteins rather than diet alone, according to a study published August 13, 2026.
Spinach, almonds, and sweet potatoes are staples of a nutrient-dense diet, prized for their vitamins and minerals. But for people living with inflammatory bowel disease, a naturally occurring substance inside those foods may act as an active driver of intestinal distress according to research from the UNC School of Medicine. The study, published August 13, 2026, in Cellular and Molecular Gastroenterology and Hepatology, points away from simple dietary choices and toward how the digestive system processes plant compounds.
Proteins Fail to Clear Oxalate
Oxalate is present in all plant foods. In a typical digestive tract, most dietary oxalate passes through the body unabsorbed and leaves in stool. Investigators found that this baseline clearance mechanism breaks down in patients diagnosed with ulcerative colitis and Crohn’s disease as detailed in laboratory findings.
Two specific intestinal transporter proteins, known as SLC26A2 and SLC26A3, are responsible for moving oxalate out of the gut tissue. Tissue samples from patients with both major sub-types of IBD showed consistently lower levels of these proteins. This reduction appeared across affected areas regardless of whether active inflammation was present at the biopsy site, and transporter expression dropped even further as tissue inflammation worsened. When these transport systems fail, excess oxalate remains in the intestinal environment.
Patients Process Oxalate Differently
One of the most striking discoveries emerged when investigators compared what patients ate with what appeared in their stool. Using the Diet History Questionnaire III alongside DNA metabarcoding—a molecular technique that detects plant species from genetic material in stool—the team evaluated 46 participants across both patient and control groups.
That accumulation signaled a deeper biological change. That told us this isn’t just about what patients eat. Something is fundamentally different about how their gut handles oxalate,
Dr. Salvador noted in findings released by the university.
Oxalate Accelerates Colitis in Mice
To test whether oxalate actively damages tissue rather than merely sitting as a bystander, researchers turned to animal and cellular experiments. Mice receiving an oxalate-supplemented diet alongside a colitis-inducing agent were 60 percent less likely to survive than animals that consumed no extra dietary oxalate as demonstrated in survival trials. In two separate mouse models genetically predisposed to spontaneous colitis, dietary oxalate accelerated the onset of disease and made symptoms more severe.
Laboratory tests on cultured cells added clarity to the mechanism.
Transporter Links to Stricturing Disease
An exploratory analysis of 131 Crohn’s disease patients connected the activity of a third transporter, SLC26A6, with a severe manifestation of the condition known as stricturing Crohn’s disease according to genetic evaluations.
Researchers Advise Against Cutting Plants
Researchers caution against abandoning plant-based foods entirely. Plants supply essential fiber, vitamins, and minerals required for general health, and individuals can consume nutritionally complete plant diets engineered with lower overall oxalate content according to nutritional guidance.