There is hardly any subject as contested in the media as what humans should eat. Usually, such discussions are devoid of actual scientific reasoning, though they all claim to be backed by scientific studies (typically without naming those studies). The colorful spectrum of suggestions ranges from eating only bananas, to avoiding "refined" sugars and red meats, to avoiding meat altogether, to eating as much meat as possible etc. Clearly, many of them are completely contradictory.
From a purely biological, evidence-based perspective, how does an optimal human diet look? In particular, I'm interested in the following questions:
- Is there a single diet that can be recommended to all humans, regardless of lifestyle, which only needs to be scaled in quantity (i.e. more physically active people should eat more of it) but not content?
- Excluding diseases, does the optimal diet for an individual depend not only on their lifestyle but also on their genetic makeup?
- Knowing nothing about their genetic makeup and living an average industrialized-society lifestyle, what is the best guess for what a human should eat?
Answers should be backed by solid reasoning and (ideally) references to verified (meta-)studies published in actual scientific journals supporting the claim. It seems strange to have to ask such a question, as one might expect it to have been answered thousands of times already, and of course it has, but the answers vary so wildly that I suspect I'm being fed hogwash mostly.