I like to find very simple guides for exploration, and in terms of food, one simple guideline is an evolutionary perspective.
What did my ancestors eat? Since my ancestors were adapted to their diet, my body may be as well. So how does it work for me if I try something similar?
The fun thing about this approach is that it covers some very different time periods, so I can find some common guidelines that runs through most of them, and some that are specific to different phases of human evolution and history.
When I look at what may be a common theme across the different phases, I see that all of them includes locally grown food, seasonal foods, an emphasis on vegetarian foods with occasional fish or meat, and food made “from scratch” (unprocessed). Since that’s what I find I am attracted to, and what works best for me anyway, it’s a good match.
Diving it up slightly further, I see that for some tens or perhaps hundreds of thousands of years, my ancestors ate partly raw and partly cooked food. It’s a good bet that the same is good for me as well, and that too is what I find from own experience. During the summer, I naturally eat more raw foods, and in the winter more cooked foods, and at any time there is a mix.
And going into the specific time periods, I know that my immediate ancestors are mostly from Northern Europe (with a few from central Europe), which means a diet of vegetables, fruit, berries, grain, fish, and some occasional meat. Again, I know this works well for me, especially if I go back to a diet free from processed sugars, if I exclude dairy, and if my main grains are the non-wheat ones (oats, barley etc.). I also find that fermented foods works very well for me.
My pre-civilization ancestors probably ate similar foods as gatherer-hunters to today, which means fruits, berries, roots, and – again – occasional fish and meat. This too works well for me, although I must say I appreciate some grains as well.
Even further back, my ancestors ate raw foods and – most likely – mostly vegetarian foods. I include raw foods in my diet, and haven’t tried it as an exclusive diet. Although it’s not a conclusive argument, I suspect that my ancestors adapted well to cooked food (since so many generations lived on it), and our bodies and bellies have changed somewhat since our exclusive raw-food days (and I know that an exclusive raw foods diet works well for many).
Mainly, this is about experimenting and trying out what works. And what works well for me now may be different from what used to work well, or works well in the future. And it’s also, to some extent, different for each of us. We have different ancestors, are of different age and health, live in different climates, have different inclinations and preferences, so it’s not surprising that what works best for our bodies differ as well.