Here are some facts about digestion that I think are worth knowing:

It is difficult to state with any precision how long ingesta remains in the stomach, small intestine and large intestine. Nonetheless, there have been many studies on gastrointestinal transit, and the list below presents rough estimates for transit times in healthy humans following ingestion of a standard meal (i.e. solid, mixed foods).

• 50% of stomach contents emptied 2.5 to 3 hours
• Total emptying of the stomach 4 to 5 hours
• 50% emptying of the small intestine 2.5 to 3 hours
• Transit through the colon 30 to 40 hours

Generally speaking, if you want to improve your digestion, increase the amount of fiber in your diet. For example, prefer an apple over apple juice, choose whole wheat bread instead of white bread, etc.