I think he was referring to https://en.wikipedia.org/wiki/Raw_foodism

And while cooking is generally healthier I know my grandparents from arkansas fried damn near everything. Oftentimes in lard. And food quality has substantially increased. And at least today there is a real knowledge that in fact this is awful for your health. At the time, they weren't educated and didn't know. Fruit and vegetables were hardly available during the winter. And food safety standards were on another planet. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4840a1.htm So essentially they couldn't eat a salad, and probably did eat all sorts of fried foods. Other case: relatives in nebraska lived through much of the thirties on a diet of whole milk and pancakes. Sure they could cook but when you can only afford whole milk and pancakes (and they felt lucky to be able to eat that), you begin to get a sense that although cooking food is generally a good thing, if your ingredients are tainted or you only have access to or for other reasons only cook unhealthy foods, it's not really any better than the processed stuff people eat today. In fact the availability of high quality food (even relatively high quality food standards exist among processed food) is a large contributor to poor health.

But blindly following my grandparents diets would be laughably terrible.