Two transporters, two sugars, one ceiling - and why the number on the gel wrapper isn't the number your gut agrees to.
The honest answer is a range, and it depends on something you can change. Glucose crosses the gut through a single transporter, SGLT1, which saturates at roughly 60 grams an hour. That is why a single-source drink stops being useful above that point, whatever the label promises.
The honest answer is a range, and the range depends on something you can change.
The ceiling
Glucose crosses the intestinal wall through SGLT1. That transporter saturates at roughly 60 grams an hour, which is why single-source drinks plateau where they do.
Two transporters
Fructose uses GLUT5, a different door with its own queue. Running both at once is why 2:1 mixes outperform single-source drinks, and why the ceiling moves.
Where it stops
What the evidence does not support is that everyone gets there. Tolerance varies, and it is the limiting factor far more often than transporter capacity is.
