Any diet that involves whole, real food instead of processed crap is going to be better for people. But I think a whole-food vegan diet might get awfully tricky to implement. (I don’t really know, however, since I’ve never looked into it.) There are two issues involved here: the first is how best to get proper nutrition, and the second is the point of the thread, mental health.
The protein concerns I raised affect the first issue only. I don’t see our protein intake as having a direct effect on mental health.
As far as the second issue is concerned, however, I see two factors we need to bear in mind. The first is an adequate fat intake, and the second is phytochemicals.
An adequate fat intake is essential, in order to provide the brain with the proper source of energy. Dr. Palmer’s hypothesis is that a high-carbohydrate diet glycates the brain and damages mitochondria in brain cells, and this metabolic damage is the cause of many different types of brain problems, ranging from the strictly mental (schizophrenia, depression) to the strictly physical (Parkinson’s disease, epilepsy).
The therapeutic ketogenic diet for epilepsy was formulated to be extremely high in fat and deficient in protein, but there is recent research to suggest that including an adequate amount of protein does not affect the therapeutic value of the diet in preventing seizures. Fatty acids do not directly reach the brain, being too large to pass the blood-brain barrier, but ketones are small enough to pass through. And this is why Alzheimer’s patients who refuse to eat a ketogenic diet can still benefit to some extent from MCT oil and exogenous ketone supplements.
But even on a diet with adequate fat in it, some people simply have mental troubles for as long as they continue to eat plant foods. The reason is that plants contain many different chemicals, many of which, such as caffeine, evolved to protect the plants from damage (caffeine is an insect repellent).
Now, if we like these chemicals, we call them “phytonutrients,” and those we don’t like are called “phytochemicals.” But regardless, these chemicals have effects, and some people are more sensitive than other people to these effects. So really, whether something counts as a phytochemical or as a phytonutrient depends to some degree on individual biochemistry.
Our own Amber O’Hearn, a prominent carnivore, is an example. She became a carnivore because of drug-resistant Type II bipolar disease (I think I have that right; she talks about it in some of her lectures available on YouTube). If she eats any plant matter, her bipolar symptoms return. As long as she stays away from plants, she is fine. This is a separate effect from whether or not she’s getting enough fat, apparently. (Dr. Ede also has symptoms that stay in remission so long as she avoids plant foods, but I don’t know whether those symptoms are mental or physical.)
The other end of the spectrum is an internist in the midwestern U.S., whom Gary Taubes interviewed for his last book. She, apparently, has to eat a vegan keto diet, because she has problems that stay in remission only if she doesn’t eat meat.
In sum, the conclusion I draw from all this is that probably the majority of people are going to see a big improvement in their mental condition simply from reducing carbohydrate intake and stimulating ketogenesis. But some people are going to need to go either meat-free or plant-free to see the further benefit that they are in need of. For various reasons having to do with what we know of human evolution, I suspect that the people who will need to give up meat are rare; it’s more likely that people will have to head towards the plant-free/carnivore end of the spectrum. And I hope that’s an objective statement, and not simply my biases showing. At any rate, however, it’s clear that people are going to have to be prepared to try both options and see which works best for them.
I’ve lost a good chunk of weight and continue to steadily lose, and I just feel good. I’ve “slipped” a couple of times (a lot of birthday cake one time, adding some nuts and seeds to my yoghurt a few times) and my body tells me it doesn’t like it. Nothing major, I just didn’t feel good. Very out of sorts, physically and emotionally.