In this aspect some relevant factors could create great variations between individuals. The case of chewing, cooking procedures and also obviously genetic factors. One of the main topics to remember is how fat intake considerably increases the required time, as well as food with many ingredients.
The process that occurs in the stomach should last about 2 to 4 hours on average. Liquids and without protein or grease content near two hours, while more variety, grease and proteins toward four or more.
Some key elements:
As a rule, baking is better than frying.
Mastication helps the stomach, and also prevents other issues like gastritis.
Oil with too much use or time doesn't present friendly properties.
After the stomach, there's also another complexity that takes place for taking advantage of any available nutrient. The time here has a longer span, from less than 24 hours until more than a week.
The food intake is, finally, a chemical interaction and like each one of them, there are better and worse; and this time we are talking about health. A good information on the subject must be welcome in the task of avoiding possible issues.