> ... However, one must also keep in mind that comparisons between 
> vegetarians and meat-eaters should be made comparing average health of 
> vegetarians to average health of meat-eaters, and many such studies show 
> vegetarians to be healthier overall than omnivores.

I want to point out that this argument is on logically shaky grounds since 
correlation does not imply causation 
(http://en.wikipedia.org/wiki/Correlation_does_not_imply_causation). There 
may be numerous other reasons behind the better health of vegetarians not 
directly related to their diet such as their overall lifestyles, etc. Such 
comparisons rarely yield conclusive information about the actual causal 
relation between two phenomena.

- Uluc