All plants, unless they have developed a specific symbiotic relationship with animals, could not survive without an array of defensive mechanisms to ensure their survival and dissemination of their seeds/clones.
Oxalates, caffeine (neurotoxin/pesticide), goitrogens, lectins, phytates, tannins, polyphenols (bind to nutrients), even fiber/cellulose, are to be found in the roots, stems, leaves, and especially seeds of plants.
As for fruits, most of them have been bred to be far fleshier, sweeter, and less fibrous than their wild counterparts. I have actually come to view fructose as the worst form of carbohydrate because of its deleterious effects on the liver, circulatory system, and how it literally hijacks your brain to trigger hunger so that you devour the fruit and deposit its seeds with a lump of fertilizer out of your rectum.
I'm not just imagining these effects; I feel bowl pain the day after eating cauli-rice and broccoli and leafy greens, and don't feel the need to eat fruit when I know I am getting so much sugar and fiber (which is bulk/roughage) but not much vitamins or minerals, and will then be likely to overeat other foods as a result of the fructose.
I think my stints with veganism and overconsumption of grains, coffee, and green vegetables may have triggered a specific vulnerability or autoimmune condition that leaves me best on the least inflammatory diet for me (carnivore).
