Does a Natural Compound in Spinach, Almonds and Sweet Potatoes Worsen IBD? What the New Gut-Inflammation Research Shows

Dietary oxalate — a naturally occurring compound present in all plant foods, including spinach, almonds, and sweet potatoes — may actively worsen gut inflammation in people with Crohn's disease and ulcerative colitis, according to a study published August 13, 2026 in Cellular and Molecular Gastroenterology and Hepatology by researchers at the UNC School of Medicine.

The research, led by postdoctoral scholar Anna Salvador, PhD, RD, LDN, in the lab of Professor Shehzad Z. Sheikh, MD, PhD, is the first to use DNA metabarcoding to assess dietary intake in an IBD population — and the findings challenge a long-held assumption that elevated intestinal oxalate in IBD is simply a matter of eating too many high-oxalate foods.

At a Glance: Key Findings from the 2026 UNC Oxalate-IBD Study

Finding	Detail	Significance
Oxalate transporter proteins (SLC26A2, SLC26A3)	Consistently reduced in gut tissue of both UC and Crohn's patients, regardless of active inflammation	Suggests a structural biological defect, not just a flare-driven change
Stool oxalate in Crohn's vs. controls	Crohn's patients had significantly higher stool oxalate despite similar plant-food consumption	Points to impaired gut handling, not dietary excess, as the driver
Animal survival data	Mice on oxalate-supplemented diet + colitis-inducing agent were 60% less likely to survive	Demonstrates causal link between dietary oxalate and colitis severity in vivo
SLC26A6 and stricturing Crohn's	Low SLC26A6 expression associated with stricturing (fibrosing) Crohn's disease	~75% of patients with low SLC26A6 had the more aggressive stricturing form
Immune cell response	Oxalate intensified inflammatory responses in macrophages and dendritic cells in cell culture	Identifies a cellular mechanism for oxalate-driven inflammation
Microbiome link	Oxalobacter formigenes, a bacterium that breaks down oxalate, is less abundant in IBD patients	Opens a microbiome-based therapeutic pathway

What Exactly Is Dietary Oxalate, and Why Does It Matter for IBD?

Oxalate is a naturally occurring organic acid found in virtually all plant-based foods, produced both by plants themselves and as a metabolic byproduct in the human body. In a healthy digestive system, most dietary oxalate passes through the intestine and is eliminated in stool without causing harm. The kidneys handle whatever small amount is absorbed into the bloodstream, excreting it in urine — which is why high oxalate intake is more commonly associated with kidney stones than with gut disease.

For most people, oxalate is a nutritional non-issue. Foods like spinach, almonds, sweet potatoes, beets, rhubarb, and dark chocolate contain meaningful amounts of it, but healthy guts manage the load efficiently through a pair of specialized transporter proteins: SLC26A2 and SLC26A3. These proteins facilitate the absorption of oxalate from the intestinal lumen into the bloodstream, effectively clearing it from the gut environment.

The UNC study found that both transporter proteins are consistently and significantly reduced in intestinal tissue from patients with ulcerative colitis and Crohn's disease — not just during active flares, but across affected tissues regardless of whether inflammation was currently present. The more inflamed the tissue, the lower the transporter expression dropped, suggesting a feedback loop where inflammation suppresses the very machinery needed to clear oxalate, and accumulated oxalate then amplifies inflammation further.

This is not a minor biochemical footnote. IBD is a group of chronic inflammatory conditions of the gastrointestinal tract, primarily Crohn's disease and ulcerative colitis, affecting an estimated 3 million Americans and tens of millions globally. Any modifiable dietary factor that demonstrably worsens disease activity is clinically significant — especially one hiding in foods that are universally promoted as healthy.

Why Do Crohn's Patients Have More Oxalate in Their Stool Despite Eating Similar Diets?

This is the central paradox the UNC team set out to explain — and their answer is methodologically rigorous.

The researchers used two independent methods to assess dietary intake. The first was the Diet History Questionnaire III (DHQ III), a validated tool for estimating habitual food consumption. The second was DNA metabarcoding, a molecular technique that identifies plant species present in stool samples by analyzing genetic material. As the UNC Health newsroom notes, this marks the first time DNA metabarcoding has been used to evaluate diet specifically in an IBD population.

Both methods reached the same conclusion: Crohn's disease patients and healthy controls were consuming similar amounts of plant-based foods. Yet Crohn's patients had significantly higher levels of oxalate in their stool.

"For the first time, we observed that IBD patients and healthy controls were eating similar amounts of plant-based foods yet CD patients still had more oxalate in their stool," said Dr. Salvador. "That told us this isn't just about what patients eat. Something is different about how their gut handles oxalate."

The implication is substantial. Previous research on diet and IBD has often struggled to separate cause from effect — do patients eat differently because they're sick, or does what they eat make them sicker? By demonstrating that oxalate accumulation in Crohn's patients is driven by impaired biological processing rather than dietary excess, the UNC team shifts the question from "how much oxalate are patients eating?" to "why can't their guts clear it?"

The answer, based on the transporter data, appears to lie in a structural defect in the oxalate-handling machinery of the IBD gut — one that is present even when the disease is not in an active inflammatory phase.

What Did the Animal and Cell Culture Experiments Show?

The human observational data alone would be compelling but insufficient to establish causality. The UNC team therefore conducted a series of controlled experiments in animal models and cell cultures to test whether oxalate was an active driver of inflammation, not merely a marker of it.

The results were striking. In a chemically induced colitis model, mice fed an oxalate-supplemented diet alongside a colitis-inducing agent were 60 percent less likely to survive than mice that received the colitis agent without additional dietary oxalate. This is not a subtle statistical signal — it represents a dramatic difference in mortality attributable to a single dietary variable.

The team also used two separate mouse models that are genetically prone to developing spontaneous colitis. In both models, dietary oxalate caused the disease to appear sooner and become more severe. The genes responsible for oxalate transport were already less active in these susceptible mice before oxalate was introduced to their diets — mirroring the pattern seen in human IBD patients, where transporter deficiency appears to precede or exist independently of active inflammation.

Cell culture experiments added a mechanistic layer. When macrophages and dendritic cells — immune cells that play central roles in intestinal defense and immune regulation — were exposed to oxalate, they showed intensified inflammatory responses. This provides a plausible cellular pathway through which accumulated gut oxalate could amplify the chronic immune activation that characterizes IBD.

Taken together, the animal and cell data move oxalate from "associated with worse IBD" to "biologically capable of driving worse IBD." That distinction matters enormously for whether dietary intervention is worth pursuing.

Could Low-Oxalate Diets Help People With IBD?

The researchers are careful not to overstate what the findings support at this stage. The study does not recommend that people with IBD eliminate plant foods from their diets — a move that would carry its own nutritional risks, particularly given that fiber-rich plant foods support gut microbiome diversity, which is already compromised in IBD.

What the findings do suggest is that in people who are genetically susceptible to IBD, even moderate amounts of dietary oxalate may contribute to intestinal inflammation through a mechanism that healthy individuals simply do not experience in the same way. A nutritionally complete plant-based diet with reduced total oxalate is achievable — it involves prioritizing lower-oxalate plant foods such as cauliflower, cabbage, peas, and most fruits, while limiting very high-oxalate foods like raw spinach, beets, rhubarb, and certain nuts.

The researchers emphasize, however, that formal dietary recommendations for IBD patients cannot be made on the basis of this study alone. Future research will need to follow larger patient cohorts over time, combining stool oxalate measurements, carefully documented dietary intake, molecular profiling, and microbiome analyses before clinicians can confidently advise specific oxalate thresholds for people with Crohn's or ulcerative colitis.

"For patients living with Crohn's disease or ulcerative colitis, this research opens a genuinely new therapeutic angle — one that connects the food on their plate to the inflammation in their gut," said Dr. Sheikh. "Diet is one of the most powerful, modifiable levers we have in medicine, and this study gives us a molecular framework to start using it more precisely."

The broader literature on plant-based compounds and IBD is detailed. A 2025 review published in Frontiers in Nutrition found that plant-based dietary compounds including dietary fibers and polyphenols can improve gut dysbiosis, increase anti-inflammatory cytokines, and improve barrier function in IBD — but also acknowledged that some plant compounds can exacerbate immune responses in certain contexts. The oxalate findings fit within this more complex picture: plant foods are not uniformly beneficial or harmful in IBD, and individual molecular components matter.

What Is the Role of the Gut Microbiome in Oxalate Handling?

One of the most therapeutically promising threads in the UNC study involves the gut microbiome. Oxalate functions here not only as a dietary input but also as a substrate for specific intestinal bacteria — and the balance of those bacteria appears to be disrupted in IBD.

Oxalobacter formigenes is a gut bacterium that specializes in breaking down oxalate. Its presence in the intestinal microbiome effectively reduces the amount of oxalate available to accumulate in the gut lumen. The UNC researchers found that Oxalobacter formigenes is less abundant in people with IBD — a finding consistent with the broader pattern of gut dysbiosis (microbial imbalance) that characterizes both Crohn's disease and ulcerative colitis.

This raises the possibility that future microbiome-based treatments could improve oxalate breakdown inside the gut, offering an alternative or complement to dietary restriction. Probiotic formulations containing Oxalobacter formigenes or other oxalate-degrading bacteria, or prebiotic strategies designed to support their growth, could theoretically reduce intestinal oxalate burden without requiring patients to dramatically alter their diets.

No clinical trials of oxalate-targeting microbiome therapies in IBD have been completed, so this remains speculative — but it represents a genuinely novel therapeutic angle that the UNC findings have opened up. The gut microbiome is already a major focus of IBD research, and the oxalate-microbiome connection adds a specific, testable mechanism to that broader effort.

The parallel with other areas of gut health research is instructive. A 2025 review in Frontiers in Nutrition highlighted how plant-based dietary compounds can modulate dysbiotic gut microbiota in IBD through multiple signaling pathways, including effects on short-chain fatty acid production and immune cell regulation. The oxalate story adds another layer: it is not just about what beneficial compounds plant foods provide, but also about what harmful compounds they contain, and whether the IBD gut can handle them.

Could Oxalate Transporter Activity Predict Disease Severity?

One of the most clinically intriguing aspects of the UNC study is the exploratory analysis linking oxalate transporter expression to disease trajectory in Crohn's disease.

The researchers found that low expression of a third transporter protein, SLC26A6, was associated with stricturing Crohn's disease — a more aggressive form of the condition in which chronic inflammation leads to scar tissue formation, causing parts of the intestine to narrow. Stricturing Crohn's is characterized by fibrotic narrowing of the intestinal lumen and often requires surgical intervention.

Nearly 75 percent of patients with low SLC26A6 expression had stricturing disease, compared to a much lower proportion among patients with higher transporter expression. If confirmed in larger studies, this association could eventually give clinicians a molecular tool to identify patients at greater risk of developing the most severe and surgically challenging form of Crohn's disease, enabling earlier, more aggressive intervention before strictures develop.

The researchers are appropriately cautious about this finding. It comes from an exploratory analysis, not a pre-specified primary endpoint, and the patient numbers are not large enough to draw firm conclusions. Replication in independent, larger cohorts is essential before SLC26A6 expression could be considered a clinically useful biomarker.

Still, the signal is notable. Stricturing Crohn's disease is notoriously difficult to manage and predict, and any molecular marker that correlates with its development would represent a meaningful advance in personalized IBD care.

What Should People With IBD Do With This Information Right Now?

The honest answer, based on where the science currently stands, is: discuss it with your gastroenterologist, but do not make dramatic dietary changes unilaterally.

The UNC study is rigorous and its findings are biologically coherent, but it is a single study. It establishes that oxalate accumulates abnormally in IBD guts, that this accumulation is driven by impaired transporter function rather than dietary excess, and that oxalate can worsen inflammation in animal models and immune cells. What it does not yet establish is the precise oxalate intake threshold at which harm begins for any individual IBD patient, or whether reducing dietary oxalate will measurably improve clinical outcomes in controlled human trials.

For people with IBD who are curious about their oxalate intake, a few practical points are worth noting. Cooking reduces oxalate content in many vegetables — boiling spinach and discarding the water, for example, removes a substantial portion of its oxalate. Pairing high-oxalate foods with calcium-rich foods (dairy, fortified plant milks) causes oxalate to bind to calcium in the gut, reducing absorption. These are low-risk modifications that align with general nutritional guidance and are unlikely to cause harm even before formal clinical recommendations exist.

What the research does not support is the conclusion that plant foods are dangerous for IBD patients. The broader evidence base — including the 2025 Frontiers in Nutrition review — consistently shows that dietary fiber, polyphenols, and other plant-derived compounds provide meaningful benefits for gut microbiome diversity and inflammation control in IBD. The oxalate story is about a specific molecule within a complex dietary matrix, not an indictment of plant-based eating.

"Dr. Salvador really conceptualized and drove this work from the beginning," said Dr. Sheikh. "She asked a question that hadn't been asked before: What if a specific dietary molecule is an active driver of gut inflammation in IBD, not just a bystander? The rigor she brought to answering it is what makes these findings so compelling."

What Comes Next in Oxalate-IBD Research?

The UNC team has outlined a clear agenda for future work. Larger, longitudinal studies are needed — ones that follow IBD patients over time while simultaneously measuring stool oxalate, documenting dietary intake with validated tools, profiling gene expression in gut tissue, and characterizing the microbiome. Only that kind of full, prospective data will be sufficient to support formal dietary guidelines.

Clinical trials of low-oxalate dietary interventions in IBD patients are a logical next step. These would need to be carefully designed to ensure nutritional adequacy and to separate the effects of reduced oxalate from other dietary changes that might accompany a lower-oxalate eating pattern. Microbiome intervention trials targeting oxalate-degrading bacteria represent another frontier. If Oxalobacter formigenes supplementation or microbiome modulation can reduce intestinal oxalate burden in IBD patients, that would provide a therapeutic option for patients who cannot or do not want to restrict their diet.

The study was supported by the Helmsley Charitable Trust, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the Chan Zuckerberg Initiative, Schmidt Sciences, the Burroughs Wellcome Fund, and additional NIH sources — a funding profile that reflects the scientific community's recognition of IBD as a major unmet medical need. Co-authors span UNC-Chapel Hill, Texas A&M University, and Duke University, suggesting the collaborative infrastructure for follow-up work is already in place.

For the millions of people living with Crohn's disease or ulcerative colitis, the oxalate findings represent something genuinely new: a specific, biologically grounded, modifiable dietary factor that connects what they eat to how their gut behaves. That connection has been suspected for decades in IBD research, but rarely demonstrated with this level of mechanistic detail. The next few years of research will determine whether it translates into something patients and clinicians can act on with confidence.

If you found this article useful, you may also want to read our coverage of natural anti-inflammatory supplements and how plant-based compounds interact with gut health.