Most of the people that are 'old' (what your basing your point on) grew up with the raw milks, butters and high cholesterol foods in the early 1900's. Maybe in 50-70 years you will have an argument, because that will show what type of impact all the synthetic foods have of today. From the looks of it though (the obesity epidemic) our life spans will be going back down.
Modern medicine that was started in the early 1900's by William Welch has alot to do with lifespans. Prior to him the human body and viruses were not clearly understood. Prior to these medical breakthroughs, doctors were sometimes more dangerous than the disease itself. Morphine overdose was quite common.
So again, all the 80/90 year olds have Mr. Welch to thank for part of their lifespan, the other part has to do with the whole foods they grew up eating...all whole foods with no synthetic agents.

I am not an advocate of current medical practices, I dont get flu shots, I dont take medicine and I dont get sick. I believe alot of medicine has harmed us more than it has helped. Naturopaths are the way to go, something the chinese have known for a long time-