My grandma just turned 94 god bless her. She still cooks and cleans every day and really only takes one pill for her arthritus. She is healther than me and I am mid 30s. LOL. She has all her wits and is awsome. She has always cooked her own meals.
It could very well be the self cooking. She knows what goes into her recipies! There is also genes, and the environment in which she grew up. The world today is much different than the time when she was young.