My wife is vegan and was top ranked body builder. She knows how to eat well. Interestingly, any medical issues she has had in the past five years have come with a recommendation to "eat less meat and exercise more" (medical staff reading instructions from a screen over the phone) I'm not vegan and I am less healthy than she is, by far. Our kid is vegetarian and is just as healthy and active as I was at her age. Everyone is different and diets impact people differently.