In a lecture of over an hour Dr Michael Greger overcomes the unfortunate timbre of his voice and delivers a fascinating exposition of why vegetarians do not outstrip meat eaters in life expectancy (http://www.youtube.com/watch?v=q7KeRwdIH04&feature=em-subs_digest-vrecs). His two conclusions, which he supports with powerful evidence and reasoning, are that vegetarians (and even more vegans) are deficient in omega 3 and vitamin B12.
An important factor in preventing oxidized inflammatory deposits in the arteries is to have a good ratio of omega 3 to omega 6. Ideally in single figures and around 6 or 7, which is the sort of ratio obtained in the much vaunted 'Mediterranean Diet'. The body through an enzyme produces omega 3 before omega 6 and so as long as enough source material is eaten then you should be all right. The best protection is to take omega 3 by supplement. This can be done by taking fish oil (make absolutely sure you take a high quality pure fish oil, because some cheap ones can have traces of heavy metals or other harmful elements), or if you are a vegetarian/vegan two tale spoons of ground flax seeds daily.
Homocysteine triggers arterial disease by instigating plaque and clot formation. For years a pathologist, Dr Kilmer McCully, discovered this, but it was only after his being vilified for years that it became orthodoxy to associate elevated homocysteine with cardiovascular disease. The way to avoid this is to take vitamin B complex (especially B6 and even more importantly B12) and folic acid.
Although only recently published on YouTube this lecture was given over 10 years ago. I take issue with Dr Greger's contention that saturated fat (as opposed to hydrogenated/trans fats) is bad. Recent research and reasoning has rehabilitated the reputation of saturated fat. I also note that in his talk Dr Greger appears to subscribe to the orthodox but erroneous idea that low cholesterol is good and high cholesterol bad.
I suggest that there are two other factors in the life expectancy of vegetarians and vegans, which Dr Greger does not consider. The first touched upon above is that low cholesterol of itself carries with it a higher risk of death (please see previous blogs).
The second is that, although farmed meat is a poor source of L-arginine compared with game meat (ancient man's nutritional source of sufficient Arginine), farmed meat is still the largest source of Arginine in most people's diet. Vegetarians, and more so vegans, are likely to be more deficient in Arginine than meat eaters. The answer is, of course, Arginine supplementation with vegan friendly Ark 1. I am not a vegan, but I am largely vetetarian (I do for instance take fish oil), and I have no doubt that that is one of the reasons that Arginine had such an immediate affect on me.