A couple of months ago, a cool study came out that showed vegetarians are more likely to have a brain shrinkage as they age. The reason is due to vitamin B12, which is mainly found in animal foods.

Furthermore, no one in the study actually had vitamin B12 deficiency, which means that merely getting the recommended amount is not good enough. A couple of posts down I talked a brain deterioration, so I guess an addendum to that post would be: EAT YOUR MEAT!

Also see here.