Did you know that everybody has cancer in them in all different parts of the body, but being vegan or smoking tobacco activates them and makes them grow...
I do not know really if being vegan is a danger for your health, I do not think so, but you have to take in count that humans are omnivorous, and most vegans usually have deficiency of some important proteins and vitamins such as B12, iron, vitamin D and omega-3 (EPA and DHA). The only times I was looking for strong points defending vegans, I unsurprisingly found them all in pro-vegan websites... Hence they aren't really unbiased sources at all.
This is my personal opinion: The key word for a perfect diet is MODERATION: Having a vegan diet only is not really a sign of good health as having a carnivorous diet only or abusing meat diet, I think the perfect diet would be a balanced diet where you eat vegetables as well as meat/fish, and this is good as long as you are not abusing any of them (I heard stories of people eating too much carots having an excess of carotene and having their skin turning yellowish... A excessive dose of carotene can be also dangerous and lethal).
