The body is not a pipe

Nutrition “science” is so unreliable that it can hardly be trusted, and for this reason, I sympathize with people who resign themselves to mystery unaided by modernity.
Despite the lack of clear information and uncontradictory advice, we face the choice between [1] believing that what we eat does indeed directly affect our health and [2] seeing the body as a pipe.
Many people eat only to quell the annoying hunger pangs or for the taste in the mouth. They presume that their digestive system is nothing more than a pipe between their tongue and their toilet, with a hunger thermostat somewhere in the middle.
But apparently the stomach and its processes is so important to our physical and psychological health that it can be described as “a second brain”.
There’s interesting research going on, and we’ll see what it tells us to do next.
But regardless of whether scientists can tell us anything interesting, I’m curious in where this pipe idea came from in the first place. How did people come to believe that food could only hurt them if it was poisoned, and that it had no healing properties (which remains a woo-woo new-age concept). As my friend Toby said, after finally removing himself from a western medicine system which could neither diagnose nor treat him. “Food is medicine.”