Americans deeply believe in the
theory that 'you are what you eat'. How valid is this driving force in
American (and German) life?
There are many peoples around the world who have had extreme food consumption practices for dozens of centuries.
The Indian Brahmans are vegetarians and have been for millennia. They also believe that eating onions increases intelligence. Here is a gigantic population of true vegetarians, tens of millions, that are virtually indistinguishable from their non-veggie neighbors. They aren't taller, faster, healthier, stronger nor longer lived. I don't know if they are smarter. So what does that tell us about vegetarianism?
'Nothing', if empirical evidence means nothing to you.
We
have more extreme examples. The Inuit eat virtually no plant life
because they live far above the Arctic circle. No problem with health,
lifespan or strength. Don't let your kids who hate spinach know about
the Inuit.
Then there are the Masai. Centuries of drinking cattle blood. They are very tall. But the same diet among the Mongols hasn't changed their height.
Then there are all people in the world who do eat pork or don't eat pork, do drink milk or can't drink milk, all the people who eat mainly rice, all the people who eat mainly fish and all the people who live mostly on Yak butter. No real correlations with anything....height, weight, health, lifespan...nothing.
So how valid is the core belief that 'you are what you eat'? Don't answer. I've never seen anyone change their mind on this issue.