Where Fructose Actually Goes

Fructose is the sugar in fruit, table sugar and high-fructose corn syrup. It has a bad reputation because very large amounts of it are linked to fatty liver, and most people assume the liver is where all dietary fructose goes. A 2018 study in Cell Metabolism tracked fructose through the body and found something different: at modest doses, the small intestine clears most of it before it ever reaches the liver. Here is what the study measured, what it did not, and why dose matters more than the word "fructose."

What the researchers did

Jang and colleagues gave mice a drink with equal parts glucose and fructose, the same 1:1 ratio found in table sugar and close to the ratio in high-fructose corn syrup. They labeled the carbons in one sugar at a time so they could follow exactly where each one ended up, then sampled blood from the portal vein, which carries everything absorbed from the gut to the liver, and from the general circulation.

This was a mouse study. The authors scaled doses by calorie intake rather than body weight and argued that the doses they used fall in the range of typical human intake. That is their reasoning, not a human trial.