Check out this graph. It's the risk of dying on a low-fat diet filled with vegetable oils (blue line) compared to a regular diet. That's right - it looks like more people die. Actually the more people lowered their cholesterol in the study, eating vegetable oils, the higher their risk of premature death!
Unfortunately the full study was never published 40 years ago - likely because the result did not match what the investigators expected. If the results had been published instead of hidden away perhaps it would have changed nutrition history. Perhaps we'd all have kept happily eating butter.
The Washington Post: This Study 40 Years Ago Could Have Reshaped the American Diet. But It Was Never Fully Published. TIME: When Vegetable Oil Isn't as Healthy as You Think