Fructose, the sugar commonly found in soda and fruit juice, is mainly metabolized in the small intestine, according to researchers from Princeton University. The results of their study, published in the journal Cell Metabolism, shed new light on previous assumptions that fructose is processed in the liver.

• In the study, researchers used isotope-labeled fructose to track how it passes through the digestive systems of laboratory mice.
• The team found that more than 90 percent of fructose was processed in the small intestine of the mice.
• High doses of fructose (at least one g/kg or higher), however, can overpower the capacity of the small intestine. The excess fructose then reaches the liver and the colon.
• Upon reaching the colon, fructose is exposed to the gut microbiome, which does not know how to process it. While the study did not show how this interaction can affect the gut microbiome, researchers believe that an effect is likely and should be studied further.
• The researchers also found that the small intestine can also process fructose more effectively after a meal. Consequently, taking in fructose in the fasting periods reduced its ability.

In an article in Science Translational Medicine, Kathleen Page of the Keck School of Medicine commented on the study’s results, saying that future studies are needed to determine how dietary fructose is processed in people since excessive consumption is linked to various metabolic disorders.

Journal References:

Jang C, Hui S, Lu W, Cowan AJ, Morscher RJ, Lee G, Liu W, Tesz GJ, Birnbaum MJ, Rabinowitz JD. THE SMALL INTESTINE CONVERTS DIETARY FRUCTOSE INTO GLUCOSE AND ORGANIC ACIDS. Cell Metabolism. 6 February 2018;27(2). DOI: 10.1016/j.cmet.2017.12.016

Page KA. TRACING THE FATE OF FRUCTOSE. Science Translational Medicine. 7 March 2018;10(431). DOI: 10.1126/scitranslmed.aas8965