In the book and movie "A Delicate Balance" http://www.adelicatebalance.com.au/about.html
it is argued that our digestive system is not really geared up to eat meat, and it draws together some health stats from various sources.
Meat eaters do live long lives sometimes though. Jack Lalanne was once asked about George Burns, the famous comedian who made it to 100 though he smoked cigars, drank alcohol, and was not health oriented. Jack, it turns out, knew George Burns well, and he answered, “George Burns was more athletic than you think he was. And he was a very social man. He loved people, he enjoyed life. He worked at living. Old George was a social lion, he got around and did things. That’s the key right there. It starts with your brain.”
So there's probably more to longevity than just diet.