The Vegan Diet may not be as great as we thought. Doing it wrong poses some dangers to your health. This blog talks about how Veganism can go wrong.

#1 Humans are not great at extracting iron from non-heme (plant-based) sources

This means after you've come off processed meat, dairy, and eggs which can be inflammatory (yes) you feel great, but 6 months down the line you get more and more fatigued and moody, and you wonder why. Most people think it's because they need to be stricter on themselves as they're "doing it wrong", not realizing they have by that point depleted themselves of iron, zinc, and vitamin A to name a few.
 

#2 So you feel great having cut meat

But that's likely because you were enzymatically and nutritionally deplete you couldn't digest meat properly.  The root issue is the nutrient debt, not meat.  
 

#3 You need to take B12 supplements, or generously supplement your diet with nutritional yeast.

B12 simply isn't found in adequate amounts in plants.  Most sensible vegans will know how to supplement synthetically.  
 

#4 You see, some people ancestrally have the right DNA for veganism

Most people don't.  So, is this diet biologically and ancestrally sound for you, if we have to supplement just for you to get by?
 

#5 Too much nuts, too much processed soy!

Too little good quality protein and amino acids...too little plant diversity in modern agricultural produce.  Being on a truly healthy high fibre, high biodiversity vegan diet IS impossible, and takes great effort, so your reasons behind it need to be robust.  I see many people, including health and wellness professionals subscribing to this narrow dietary range, hoping it is a panacea for their ails, but get deeper into nutritional debt instead.