All the vegetarians I know are anemic, have joint deteriation and sick most of the time. You really have to hit the vit/min supplements hard and know what you are doing to stay healthy. We are omnivores and when any species deviates away from how thier digestive tract was designed there will be serious problems. Getting enough amino acids and cyanocobolamin (B-12) is very difficult w/o meat.
The healthiest diet is to eat the way your ancestors did. An Asian would not do good on an Eskimo diet and vice-versa. Our digestive tracts have adapted over a very long time to a certain diet. When you start monkeying around with those adaptations there will be problems.
The only meat I eat is small farm raised and does not have homones, pesticides,dyes and antbiotics in it.