Some of the healthiest plant-based foods on the menu – including spinach, beetroot, rhubarb, almonds and sweet potatoes – may be linked to inflammatory bowel disease (IBD), according to a new study.
The study comes from a team led by researchers at the University of North Carolina and focuses on a natural compound found in all plant-based foods called oxalate.
Although oxalate is not very useful in the human body, it is also not harmful in itself: we simply get rid of most of it as waste. But this latest research indicates that in some people, problems processing the compound correctly can lead to intestinal problems.
Part of the study, published in Gastroenterology and cellular and molecular hepatologymeasured the level of oxalate in a person’s diet compared to what appears in their stool. Two different analysis methods were used on a total of 46 participants, including some with Crohn’s disease (CD), one of the two main subtypes of IBD.
“For the first time, we observed that IBD patients and healthy controls ate similar amounts of plant-based foods, but CD patients still had more oxalate in their stools,” says Anna Salvador, a gastrointestinal biologist at the University of North Carolina.
“That told us it wasn’t just about what patients eat. There’s something fundamentally different about how their gut handles oxalate.”
The researchers also studied transporter proteins called SLC26A2 and SLC26A3, which absorb oxalate from the intestine. In several hundred tissue samples taken from people with CD, ulcerative colitis (the other main subtype of IBD), and healthy controls, the genes producing these proteins were found to be less active in the IBD samples.
Another aspect of the study involved testing mice with intestines that were deliberately inflamed (to resemble IBD). These experiments showed that animals fed additional oxalate fared worse on several criteria: they lost more weight, developed a greater level of intestinal inflammation for a longer period of time, and were less likely to survive.
The researchers even had time to examine the reaction of mouse immune cells to oxalate in the laboratory. The compound increased the inflammatory response, suggesting that this is an immune system reaction rather than direct damage linking oxalate and IBD.
“These results identify dietary oxalate as a potentially modifiable factor in intestinal inflammation and highlight the need to consider variation in dietary exposures and oxalate metabolism in inflammatory bowel disease,” the researchers write in their published article.
))>Possible next steps in research include attempting to target the transporter proteins SLC26A2 and SLC26A3 as a means of ensuring that oxalate is efficiently cleared from the intestine, rather than reaching harmful levels.
Along the same lines, the researchers also studied a third oxalate transporter protein, SLC26A6. In a review of 131 people with Crohn’s disease, a less active SLC26A6 gene was associated with a more severe type of the disease.
“For patients with Crohn’s disease or ulcerative colitis, this research opens a truly new therapeutic angle,” says geneticist Shehzad Sheikh of the University of North Carolina. “The one that links the food on their plate to the inflammation in their gut.”
It is well recognized that diet plays a role in IBD, alongside several other key factors, and oxalate found in plant-based foods may be one of them. The researchers are not suggesting that these foods should be removed from anyone’s diet, but that moderate oxalate consumption may be beneficial.
Eventually, it’s possible that additional supplements—perhaps promoting bacteria that help the body get rid of oxalate—may become part of the treatment options for IBD. Studies with larger groups of participants should tell us more about the potential mechanisms at play and identify those who might be more sensitive to oxalate.
“Diet is one of the most powerful and modifiable levers we have in medicine, and this study gives us a molecular framework to start using it more precisely,” says Sheikh.
The research was published in Gastroenterology and cellular and molecular hepatology.
This article was fact-checked by Rachel Garner and edited by Fiona MacDonald. Although we are proud of our process, we are only human. If you spot an error, please let us know.
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