The distinction between foods as fasting and non-fasting is obviously based on their nutritional properties. Foods with proteins and lipids (= non-fasting) and foods without lipids and with fewer proteins (= fasting).

In other words, the division of foods (which all belong to God) is made entirely biologically! There are no good and bad foods. Foods of God and foods of the devil! Pollution is the violation of God's will, not "some spiritual germ" that we catch ("tainting ourselves"!) from non-fasting foods!!

And of course, we must always keep in mind what the Jansenists were accused of in the Middle Ages: "Pure as angels and proud as devils"! Fasting is obedience to the Church's way and assistance in the struggle for the right path to integration into the body of the Saints, who make up the Church.