News at 11: cancer is a natural occurrence. You could exclusively eat prime quality fish, raw organic fruits and veggies and still get a heart attack at 52 and cancer at 58. In other news, I seriously question the idea that paleolithic humans had incredible food wisdom and perfect health. They probably ate whatever the hell they could find at a given time of the year in their immediate environment, and that was probably hugely lacking in nutritional value when it's the winter, all the plants are dead and most animals hibernating.
I agree that making an effort to eat well is a good idea, but it doesn't make you immune to diseases, and diseases are not necessarily a result of bad habits. There is also a huge amount of conflicting information as to what is healthy food.