A Hidden Compound in Healthy Foods May Worsen IBD

New research from the UNC School of Medicine suggests that a naturally occurring compound found in healthy foods such as spinach, almonds and sweet potatoes may worsen intestinal inflammation in people with inflammatory bowel disease (IBD). The study, published August 13, 2026 in Cellular and Molecular Gastroenterology and Hepatology (CMGH), was led by postdoctoral scholar Anna Salvador in the lab of Dr. Shehzad Z. Sheikh, professor of medicine and genetics.

The compound, oxalate, is found in all plant foods and normally passes through a healthy digestive system to be eliminated in stool. The researchers found that two transporter proteins that move oxalate out of the gut, SLC26A2 and SLC26A3, were consistently present at lower levels in intestinal tissue from patients with both ulcerative colitis and Crohn's disease, regardless of whether active inflammation was present -- and the more inflamed the tissue, the lower the transporter levels tended to be.

One of the most striking findings involved people with Crohn's disease, who had significantly higher levels of oxalate in their stool than people without IBD, even though both groups reported eating similar amounts of plant-based foods, measured using a validated dietary questionnaire and, for the first time in an IBD population, DNA metabarcoding of stool samples. "That told us this isn't just about what patients eat. Something is fundamentally different about how their gut handles oxalate," said Dr. Salvador.

In animal experiments, mice fed an oxalate-supplemented diet along with a colitis-inducing substance were 60% less likely to survive than mice without the added oxalate, and in two mouse models genetically prone to spontaneous colitis, dietary oxalate caused the disease to appear sooner and become more severe; the mice already had lower activity of the oxalate-transport genes before oxalate was added to their diet, mirroring the pattern seen in people with IBD. In an exploratory analysis, low expression of another transporter, SLC26A6, was associated with stricturing Crohn's disease, a more aggressive form in which scar tissue narrows the intestine; nearly 75% of patients with low SLC26A6 expression had this stricturing form, though the researchers say the finding needs confirmation in larger patient groups.

The results do not suggest that people with IBD should eliminate plant foods from their diets. Certain intestinal bacteria, including Oxalobacter formigenes, can break down oxalate but are less abundant in people with IBD, raising the possibility that future microbiome-based treatments could help the gut process oxalate more effectively.