What health benefits are associated with a vegetarian diet ?

Good to know: The big studies have not shown increased longevity or much protection from any of the common cancers or vascular diseases just from vegetarianism / veganism. These people do tend to have other healthy habits. I admire the moral statement against the cruelty of factory farming. If you do not supplement (b12, several others) you will ruin your health -- your physician can guide you.