JeffroDH t1_ja8bxwn wrote on February 27, 2023 at 4:27 PM

Reply to comment by dshookowsky in ELI5: If food takes 6-8 hours to fully digest and make it to the small intestine, how come food you eat now affects the qualities of feces from food eaten 8 hours ago (i.e. having to use the toilet soon after eating)? by [deleted]

This is the answer. For ELI5: When you put food into your stomach, the stomach stretches. The stretching causes signals to be sent to other parts of the body to prepare it for digestion. Among these signals is the gastrocolic reflex mentioned above.

This causes the movement (motility) of the large intestine and colon to increase, which tends to result in a bowel movement.

secretactorian t1_ja93smu wrote on February 27, 2023 at 7:23 PM

Yes, and it is unlikely that what you are 8 hrs prior is making it's way out of you. After the small intestine is the large intestine, and then you can poop it out. Gut motility varies from person to person, and "normal" can be anywhere from 16 hrs - 2 days to get through your system.

Curious how long yours is? Eat corn and see when it passes. Or eat a bunch of beets and wait till you see purpleish-red poop!