What is best for my health? PETA supporters will, and they’re right, cry in my face that it’s better for my health not to eat meat. An average well-groomed man from the intelligent layer in the middle class will claim the opposite. Whom should I believe? I don’t have the knowledge to do the research on my own, and there are tons of information supporting both beliefs.
Ouch...I'm a vegetarian and I like to consider myself an "average well-groomed man from the intelligent layer in the middle class"...
Vegetarianism with adequate supplementation is a perfectly healthy choice for a longevity-oriented diet
A) if you have moral concerns regarding the mass slaughter of animals
B) if you simply want to avoid consuming red meat or industrial farm animals out of health concerns (casein, hormones, etc)
I take some personal exception to the current paradigm in which avians and mammals are raised, systematically abused, and "processed" via the machinery of the world's industrial farming.
From a biological and evolutionary standpoint, what makes us different from some of the creatures we process this way is VASTLY less than what makes us similar, and the mind-bogglingly massive amount of resources used to raise and sustain animals for meat has a negative and widespread impact on the environment, so I think there are fundamental ethical, social, and environmental concerns that can't easily be dismissed.
On the other hand, some of the rhetoric from animal-rights groups can be a bit servile to their own rigid dogma to the point where they sometimes assert things that fly in the face of accumulated scientific evidence (such as denying that meat-eating and hunting played an important role in human evolution). Some of these individuals don't seem to realize or adequately appreciate the fact that mankind has been hunting and eating animals
since before civilization existed, and that hunting can be a natural, even harmonious expression of mankind's basic place in the natural world.
Personally, I'm an Octo Lavo Vegetarian; while I do eat cheese, yogurt, and creams (such as sour cream), I exclude cow milk as a standalone beverage. While there are some benefits to yogurt (as a probiotic, for example) it does not have the lactose that milk does. I don't have any personal ethical concerns about consuming lower animal organisms which is why I sometimes take a Krill Oil supplement (though I do have some concern about the over-harvesting of krill and its effect on arctic ecosystems).
Even if you have no moral/ethical concerns about the humane treatment or mass slaughter of animals, my understanding is that heavy meat consumption is linked to increased risk of disease and reduced longevity (particularly in relation to casein, a serious cancer causing molecule), whereas the health benefits of vegetables and fruits are innumerable.
The bottom line is that if you want to reduce your risk of disease and maximize your potential for long life, then it would be prudent to eat a diet of mostly plant foods and limit or reduce your consumption of animal products.