It's been 2 years since I've been able to do Raw Primal. I think
Thats a pretty long time. Raw fish, milk, eggs give me the same symptoms too unfortunately. Also ive done all the diets there is around town. Keto, paleo, plant based. Plant based was easily the WORST one. Never again.
If this is the case, I can think of a few causes some of which you already suspect:
1. Enzyme deficiency. Maybe raw honey, lemon, and ginger would help (to digest sugars, fats, and proteins respectively)
Protease deficiency is my best guess because the standard diet is mostly carbs and fat. Ginger also can relieve depression related to inflammation so raw ginger might be a remedy for these feelings.
2. Detox. It sounds like you might have not completed a healing cycle when fasting. Having read "Fasting and Man's Correct Diet", the author cites many cases where it is imperative that a longer fast is not broken when the body is not ready, otherwise it will not be able to digest food properly or at all until the cycle is completed. Maybe with all that fasting you initiated one of these "healing cycles" where the body requires all energy to complete (little left for digestion).
3. Gut bacteria is somehow off. (related to detox). Maybe you dumped something toxic into the gut to eliminate. When eating certain biologically alive foods (i.e. NOT the standard diet) bacteria is introduced but the toxins alter it into 'bad/toxic' bacteria causing depression. Far fetched but maybe somehow plausible.
4. Gut bacteria is somehow off (theory 2). Your bacteria changed somehow and responds now negatively when not fed the diet you grew up with (standard diet). Similar to withdrawal, your body (mostly bacteria) is putting up a serious fight when you eat foods that are far from what it has consumed for most of your life. Hence why plant based with lots of plant fibers being the furthest from the standard diet would cause you the most grief.
5. Dariorpl's theory/Not directly related to diet. Perhaps how you approach diets is wrong. Maybe you're able to bypass this wrong mindset when you're not thinking about how or what you're eating.
Also, when eating clean food, you're removing a veil of food intoxication. Could be that the depression is linked to you experiencing a heightened and more sober reality.. one without food to numb the harshness. Not sure about this one but sounds somehow plausible