There are some excellent tips here on the topic. One has to consider vegetarianism on an individual basis. Not everyone absorbs nutrients equally and must make adjustments. Protein isn't the main issue with most people I think; protien is very easy to obtain. Vitamins are though, and these can be very tricky.
Every time vegetarianism comes up, the Dalai lama's eating habits are evoked. As a Theravada, I couldn't care less what the Dalia Lama says or does (there, I said it
), though respect his efforts toward world peach and think China's treatment of Tibet is monstrous . But ... My wife practices Tibetan Gelukpa and thinks whenever there's a rainbow here in Bloomington, it's because His Holiness is in town and meditating. She also eats more beef than three Texans. The Buddha is my teacher, and in all matters I ask, what did Buddha teach, not what did people who lived after the Buddha teach. Sorry if this seems rude. Just what seems practical. But I'm onea dem grumpy Theras.