A naturally occurring compound in foods widely considered healthy — including spinach, almonds, and sweet potatoes — may aggravate gut inflammation in people with inflammatory bowel disease, according to researchers who found that the intestines of patients with Crohn's disease and ulcerative colitis appear to process the substance differently than those of other people.
The compound is oxalate, a molecule abundant in many plant foods. In most people, oxalate passes through the digestive tract without triggering problems, and some of it is broken down by gut bacteria. But the new findings suggest that in IBD patients, the intestine's handling of oxalate diverges in ways that can intensify inflammation rather than keep it in check.
The work points to a possible explanation for why some patients flare even when they follow diets generally regarded as anti-inflammatory. Foods rich in oxalate are frequently recommended as part of a balanced, plant-forward eating pattern, yet the same foods may be problematic for a subset of people whose gut environment is already compromised.
According to the researchers, the discovery could open the door to lower-oxalate diets designed specifically for people with IBD, as well as microbiome-based treatments tailored to individual patients. Rather than a single dietary rule for everyone with Crohn's disease or ulcerative colitis, the findings suggest that oxalate metabolism could become one of the factors clinicians consider when personalizing nutrition advice.
Crohn's disease and ulcerative colitis are chronic conditions in which the immune system attacks the lining of the digestive tract, causing symptoms that can include abdominal pain, diarrhea, fatigue, and weight loss. Treatment typically combines medication, sometimes surgery, and dietary adjustments, but diet guidance in IBD has remained unsettled because patients respond differently to the same foods.
The new research adds oxalate to a growing list of dietary components whose effects may depend on the gut microbiome — the community of bacteria and other microbes living in the intestines. Some microbes can degrade oxalate, and the composition of that microbial community varies widely between individuals. If IBD patients harbor fewer oxalate-degrading bacteria, or if their intestinal lining absorbs the compound differently, oxalate could accumulate and interact with an already inflamed gut.
The researchers caution that the finding does not mean spinach, almonds, or sweet potatoes are unhealthy for the general population, nor that everyone with IBD should avoid them. Oxalate-rich foods also supply fiber, vitamins, minerals, and other compounds with established benefits. The concern is specific to patients whose intestines handle oxalate in the altered way the study describes.
That distinction matters for clinical practice. Patients managing IBD often search for dietary changes they can make on their own, and broad restrictions can lead to nutritional deficiencies if adopted without medical supervision. The study's authors instead frame lower-oxalate eating patterns as a potential targeted intervention — one that would need to be matched to patients most likely to benefit.
The same logic applies to the microbiome angle. Treatments that adjust gut bacteria to improve oxalate breakdown would represent a more precise approach than simply removing foods from the diet. Such therapies remain experimental, and the researchers present them as a direction for future work rather than an available option.
For now, the findings add nuance to the idea that foods labeled healthy are universally beneficial. In IBD, the effect of a given food may depend less on the food itself than on how a patient's digestive system and microbial community process it. The researchers say the next steps include clarifying which patients are most affected and testing whether reducing oxalate intake or altering the microbiome changes the course of inflammation.
