What makes it difficult is that there are some who do well as vegans/ vegetarians. Whether that's the result of knowing how to target supplements, genetics, or both, the cultish approach to the particular WOE with agendas beyond health makes it difficult to get any followers to admit to poor health due to their eating choices. Some with poor health would never admit or acknowledge diet as the root cause. As mentioned, if started when young, the slow deterioration of health over time doesn't always become apparent until it's too late. Denise Minger is one who has been blunt about the shortcomings and health risks (aside: haven't heard from Denise in a while, hope she's well), and there are probably more as Dr. Ede was a former vegan/ veg follower. Many come to the realization that essential nutrients come from a variety of foods from animals, and if you don't survive your diet, you won't be around to save any other life forms.