Have you tried just eating many different things in moderation? Fiber has been repeatedly shown to decrease rates of cardiovascular disease, cancer, and all cause mortality. It’s kind of silly to “go carnivore” and use your resulting feelings as a base measurement of success after being vegan. Especially considering many of the benefits of fiber are longer term.
E.g. If you ate a diet of 100% candy bars then switched to vegan or “carnivore”, of course you would “feel better” and your “weird health issues” might go away, but that doesn’t mean either of those diets is the optimal diet for you. They are just better than eating 100% candy bars…
Following an 100% vegan diet in a healthy way requires more care in choosing some appropriate nutritional supplements and in planning what you eat than for any other kind of diet.
I am vegan and I enjoy it, but I would not recommend this for everyone, because there is no doubt that it would be too tedious for most people, who prefer to eat in a more spontaneous way, without needing to ponder whether what they happen to eat has an adequate nutritional content, taking into account what else they had eaten that day.
You can see this just by plugging 2000 calories of meat in Cronometer and viewing the nutrition holes.
Bioavailability is something vegans practically refuse to acknowledge let alone discuss.
I know the charlatans won't. We'll just get petri dish and rat studies but mostly hand-waving narratives.
> Overall these are plants defense mechanisms
This doesn't mean anything. Of the "anti"-nutrients that survive basic cooking, most of them show improved health outcomes in humans: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7600777/
Though I'm not sure how people find it convincing on a rhetorical level. If these "defense chemicals" are so bad, then over what time period are they supposed to hurt us? 100 years? Because the overwhelming balance of evidence only shows improved health outcomes with the consumption of fruit and vegetables, especially the scary ones like dark leafy greens and legumes.
This just sounds like the "eek, a chemical in my food!" rebranded for the 2020s.
Finally, to circle back to the topic at hand, I just wouldn't center my diet around rhubarb leaves. They're about as enticing as celery leaves.
Overall these are plants defense mechanisms. We know they work well as anti bug measures, ruminants have more complex digestive systems to break them down; it's not always clear what prolonged use on humans will cause.
Carnivores advocate against eating oxalates rich food and when you start a diet with no oxalates you will experience some weird symptoms, you can read about oxalates dumping: https://www.doctorkiltz.com/oxalate-dumping
There are plenty of people with "auto immune incurable" diseases who stopped eating vegetables and were relieved of their symptoms.
I personally started experiencing problems after 10 years of a 95% vegan diet and went carnivore, getting rid of a number of weird health issues I couldn't explain.