A lot of Vegans will not take anything into their bodies except fresh organic food. Some will absolutely not take even garlic or onions because they consider it a poison along with other herbs and especially any and all vitamins. They believe in the body's ability to help itself through fasting and thereby eliminating toxins. I personally think herbs are terrific but I have even heard an herbalist whom I have a whole lot of respect for say that comfrey is somewhat poisonous and should not be ingested but used as a poultice or in creams and ointments.