Your body is like a factory,
manufacturing daily energy units that you need to do what you need to do, and
energy units to protect you from pathogens, toxins, and other trouble.
and thirdly, that in case something did get through… that you heal fast.
Your doctors are mostly trained to give you tools to fix what is already visibly wrong with your body. It’s clear that asking your doctors about prevention won’t do you much good: they will repeat the party line: eat well, move you body, sleep well.
Even though in essence that is good advice, if you asked about details, you would not get much. When you repeat the party line, you have no idea what you are saying, so they don’t.