Hi Diane, 
I was surprised to read your post, then a paper by Dr. Tanzi. He also claims
that diabetes and obesity are on the rise following the advent of
refrigeration, which (he claims) has led to increased meat consumption. He
then points to several forms of dementia that he also blames on meats. The
only one that I agree with is mad cow or Creutzfeldt-Jakob disease. 

While I think that he is mostly arguing from false premises, there is some
value in what he says. Obligate vegetarian species, such as ruminants, are
unlikely to develop dementia unless they are fed animal products. (You may
recall that mad cow disease began with raising the protein content of cattle
feed by mixing waste products from slaughter houses into their feed.) 

A number of studies have emerged over the last decade or so, relative to
Alzheimer's, Parkinson's, vascular dementia, and other such neurological
diseases, showing that a ketogenic diet is neuroprotective, and that, when
caught early, a high fat, moderate protein diet can reverse these
conditions. 

Against that backdrop, Dr. Tanzi's arguments are weak.  

Best Wishes, 
Ron