Certainly Dr Donald Mallard thinks that vegetarianism is the healthiest of diets, but he's more of a medical examiner than a nutritionist.
I enjoy vegetarian foods and, for more than six months, went completely vegetarian. This wasn't from any conviction that it was healthier or more humane, but because I found an interesting vegetarian cookbook and wanted to try it out. I still use some of the recipes occasionally.
Humans are omnivores and our bodies have evolved in a manner that draws much benefit from a mixed diet. Vegetarians, especially Vegans, may find themselves deficient in vitamin B12, for instance.
So when Christmas dinner comes around I'll join with the majority of the population and say, "Make mine meat!"