This focus with what we eat and prolonging our life span through healthy lifestyle is very recent and only affects the affluent in very well developed societies. This is because everyone else lives in societies and circumstances where you better eat whatever you can or you will probably starve to death. I assume this is why we were made omnivores, to increase our chances of survival.
I have no quarrel with the Vegan or Mediterranean diets and also believe their proponents are right, that if you are destined to be long lived, either will probably enhance that longevity. However, I find it highly unlikely that those in the 65+ age range will be able to embrace either diet 100%. Add to that the fact that some of the food in both diets is becoming contaminated and the odds further diminish. By contamination, let me relate the following about my husband, Jim. The last time I brought home vegetarian sushi he refused to eat it because of the seaweed around it because it came from the Pacific Ocean and the contamination issues about food found there (the radiation from the Japanese nuclear leak being a big factor). When I mentioned anchovies the other day to him, I got the same response but I said, "Aren't anchovies found in the Mediterranean Sea?" He agreed that might be true in which case they may be ok.
So now, along with weighing a plant based diet vs a Mediterranean based one, I also have to weigh which ocean was used?! That opens up a whole other avenue of controversy over what was used on the food. What kind of chemicals were used on the plants? Were antibiotics used on the cattle or the poultry? And so forth and so on.
Although I had many philosophical problems with Catholicism at that point, it was hamburger deprivation which led to my leaving the religion at age 19. Thus when someone, like PETA, wants to tell me that I am an immoral person (translate "mortal sinning" person) because of which food I eat, it really takes me back to the days when Catholicism made a chump out of me with the "infallible" no meat on Friday rule. Extreme 100% conversion demands raise my hackles immediately for if there is one thing I do think is bad for you, it is extremism. PETA in the food movement currently occupies that too extreme position for me.
There are more moderate voices in the what you eat based health movement and these are the ones I presently heed. For example, Mark Bittman of the New York Times follows a part time vegan approach. He eats vegan up till 6pm every day and allows himself to eat other foods after that.
Bittman's cookbook is VB6. This means he is eating 14 vegan meals each and every week, which is considerable. There is also a cookbook The Part Time Vegan by Cherise Grifoni. She calls such an adherent a Flexitarian. Pop singer Beyonce is one of the adherents of this movement. Both books are pictured to the left. The flexitarian option also removes any elements of a religious conversion to one's dietary choices. If one is only doing it part time, it is impossible to claim any moral higher ground. There are after all no part time Catholics, no part way mortal sins and no part time atheists. The above two books are now on my to-be-read list (TBR) and since I am already eating and cooking this kind of food part time, they should be a logical next step.
In conclusion, I believe there are many seniors like me who would like to add healthier eating to their to-do list but expecting 100% conversions to anything at this late date is just too daunting an ordeal.