In the 1930's, 80% of men in the U.S. smoked cigarettes. And despite the fact that the tar content of cigarettes was much higher then than it is today, the death rate from lung cancer was actually extremely low. Then, in the 1950's, doctors determined that Polyunsaturated Fats (i.e. vegetable oils) were beneficial in the protection against heart disease--this was undoubtedly due more to a strong Vegetable Oil Lobby than actual education since fewer than 6% of MD's receive any form of nutritional education--and deaths from lung cancer saw a dramatic increase. By the 1980's, the number of American men who smoked had dropped down to 30%. Unfortunately, Polyunsaturated Fat Consumption was 400% higher than in the early part of the century.
Lung cancer deaths were 6000% more common.