You must read The Vegetarian Myth by Lierre Kieth: http://www.bookdepository.com/Vegetarian-Myth-Lierre-Keith/9781604860801
It's an excellent book, well cited and rich in information, presenting a factual viewpoint that my vegetarian-of-17-years self had to stand up and take notice of. Such a complicated topic, this book really opened my eyes. Needless to say i am no longer a vegetarian.
Added By J. Cho: Excerpt:
[The book] exposes the destructive history of agriculturecausingagriculture causing the devastation ofprairiesof prairies and forests, driving countless species extinct, altering the climate, and destroying the topsoilandtopsoil and asserts that, in order to save the planet, food must come from within living communities. In order for this to happen, the argument champions eating locally and sustainably and encourages those with the resources to grow their own food. Further examining the question of what to eat from the perspective of both human and environmental health, the account goes beyond health choices and discusses potential moral issues from eatingoreating or not eatinganimalseating animals. Through the deeply personal narrative of someone who practiced veganism for 20 years, this unique exploration also discusses alternatives to industrial farming, reveals the risks of a vegan diet, and explains why animals belong on ecologically sound farms."