Study finds fructose may prompt the small intestine to absorb more fat

Sugary drinks may do more than add calories, according to a U.S. study that examined what fructose does inside the small intestine. Researchers found in genetically modified mice that fructose metabolism could encourage the intestine to absorb more fat from food.

The study, led by the University of California, Irvine and published in Science Advances on Aug. 28, focused on high-fructose corn syrup. When the mice’s ability to metabolize fructose in the small intestine was blocked, they gained less weight and body fat after consuming high doses of the syrup. They also showed better insulin sensitivity.

The researchers traced the effect through the gut. Fructose metabolism changed the intestinal microbiome, which in turn affected macrophages and promoted the growth of lacteals, the tiny lymphatic vessels responsible for absorbing fat. Mice that lacked the key fructose-metabolizing enzyme KHK-C had shorter lacteals in the ileum and absorbed less fat. Some dietary fat passed out in their feces instead.

A follow-up gut-microbe transplant experiment also supported the role of the microbiome in this metabolic chain. The researchers stressed, however, that the evidence comes from mice exposed to high doses of fructose. It does not show that people would experience the same degree of change in fat absorption, and people should not try to block fructose metabolism with medication on their own. Until human studies confirm the mechanism, the article points to reducing sugary drinks and high-fructose syrup as the more direct health measure.