Structural Integrity and Active Enzymes in Food
Most food, like our lives, is very perishable. When it is exposed to temperatures above 105 degrees it starts to rapidly break down, just as our bodies would if we had a fever that high.
One of the constituents of foods that can break down are enzymes. Enzymes, of course, help us digest our food. Enzymes are proteins, though, and have a very specific three-dimensional structure in space. Once they are heated much above 105 degrees this structure can change. Enzymes function very similar to a lock and key and once their shape is changed the key no longer works and they are no longer able to provide the function for which they were designed.
This may be a major factor that explains why cooked foods contribute to chronic illness, as their enzyme content is damaged and thus requires us to make our own enzymes to process the food. Many people gradually impair their pancreas and progressively lose the ability to digest their food after a lifetime of processed foods.