The 100% vegan diet has failed my body in just after 3 months ( i attempted the diet last year - inspired mostly by the book the China study - the most incomprehensible nutritional book ever written ). It also crippled my sister menstrual cycle and gave severe muscle twiching to my father. Maybe you could try abit longer, like 6 months to assess whether vegan diet is suitable for you. All the above sickness were almost gone when we switched our diet back to our traditional onmivores diet with big time restriction on sugar ,soy, refined carbohydrate and fried food (like fried tofu or chicken).
My advice or lesson from previous experience if you are so determined to give veganism a trial:
1 ) Dont overeat non fermented soy like tofu or soy milk, Dont ... your thyroid may not like it
2 ) Match your caborhydrate intake with physical activities.( otherwise you are going to have problem with weight )
3 ) EFAs (like organic flaxseed and primrose oil)
4 ) B12
In addition, you can also learn from
Chet and Dr Ben kim on their experience ofstict Veganism .
Vegan Diet: Recipe for Disaster?