That was @badideajeans btw
There’s nothing that we “are intended to do biologically”. There is “what we’ve evolved to do”, and that’s it. Plants were not put on Earth just for human consumption, they’re here for the same reason we are, just for the sake of surviving, hence why many are indigestible and/or poisonous to animals. And if meat were indigestible, it would cause diarrhea i.e. the opposite of sitting in your gut forever. Fibre is indigestible, which is exactly why it works the way it does. In terms of nutrition, no foods are inherently good or bad. All foods have good and bad stuff in them. Even plants contain toxins. And no, cleanses will not help your body get rid of these toxins, nor do you need them to. Luckily, you have a liver, and if it didn’t work, you’d be dead.