Some are good for us, like those in a cabbage. Others have poisonous effects, at least if given in too large doses, or too long. Hence, plants are containers of chemical substances that demand that we get a good, broad enough picture of things and what is at stake. In addition to general competence, very much varies with the individuals. Such factors as size of inner organs and how effectively they may work in an individual need to be taken into account.
Some vital organs get less effective with age as well.
A bunch of quite needed cautions Things depend on part on where on the globe you live, under what conditions you are. It can be dangerous. Try to get competent persons select plants, fair and fit dosages, ways of intake and length of 'plant uses' for you. That could work better than if you try it on your own for a year and half. Don't overdo it.