High Fructose Consumption and the Unexpected Role of the Small Intestine

A UC Irvine study provides evidence that dietary sugar intake in the form of fructose is a key culprit affecting how the body — in particular, the small intestine — handles other nutrients such as fat.

Can inhibiting the metabolic breakdown of fructose in the small intestine mitigate fructose-induced obesity and insulin resistance?

Researchers from UC Irvine are exploring this possibility after their experimental study resulted in a surprise finding. “We found an unexpected role of the small intestine when it is exposed to dietary fructose,” says Cholsoon Jang, PhD, an associate professor of biological chemistry who leads the Nutrient Metabolism & Disease Lab at the UC Irvine School of Medicine.

“The fructose actively reshapes gut bacterial composition, small-intestinal architecture, dietary fat absorption and, ultimately, whole-body metabolic health,” says Hosung Bae, PhD, a former postdoctoral fellow in the Jang lab who co-led this study and is now an assistant professor of medicine at the University of Iowa School of Medicine.

The findings appear in the paper, “Intestinal Fructose Catabolism Promotes Obesity and Insulin Resistance via Ileal Lacteal Remodeling,” published on Aug. 28, 2026, in Science Advances.

Fructose and the Small Intestine

“HFCS — high-fructose corn syrup — consumption is a risk factor for obesity, diabetes, fatty liver disease, cardiovascular diseases and cancers, yet the underlying mechanisms, especially at the specific organ level, are incompletely understood,” explains Miranda Lopez, lead author of the paper and a PhD candidate in the Department of Biological Chemistry. “Hence, our research targeted specifically the small intestine’s fructose catabolic capacity.” Their work also addresses how fructose consumption influences the absorption of other nutrients, such as fat.

Using genetically modified mice, they blocked fructose breakdown specifically in the small intestine, which protected the mice against fructose-induced obesity and insulin resistance. Further studies revealed that these mice showed reduced dietary fat absorption due to shortened lacteals, which are the intestinal structures needed to absorb fat.

“The shortened lacteals are due to altered gut bacterial composition and particular immune cell types, such as macrophages in the intestinal villi,” says Lopez. “This revealed how the intestinal architecture, gut-immune landscape and gut bacteria work in concert to regulate dietary fat absorption and how excessive fructose consumption can interfere with it.”

The findings reinforce the idea that added sugars in our diet, mainly in the form of fructose, contribute to the prevalence of obesity, diabetes and certain forms of liver disease.

“Specifically, this research suggests that altered intestinal lacteal architecture likely contributes to the synergistic effects of high sugar and fat on metabolic disorders,” says Lopez. “It may also be relevant to the clinical evidence that pharmacological suppression of fructose catabolism mitigates diet-induced obesity.”

Next Steps

Further studies are needed to better understand how HFCS consumption rewires the gut microbiome in an intestinal segment-specific manner, influencing lacteal integrity and dietary fat absorption.

“Looking forward, identifying specific microbiome species that promote villus macrophage populations and lacteal growth will be crucial in developing new probiotics to therapeutically modulate dietary fat absorption,” says Jang. “This could then help identify new ways to prevent and treat metabolic disease.”

— Shani Murray