Scientific American included the following article in its April 25 e-mail: https://www.scientificamerican.com/article/records-found-in-dusty-basement-undermine-decades-of-dietary-advice/?WT.mc_id=SA_HLTH_20170425
It is a bit difficult to summarize and the article isn’t that long, so do read it. Here’s the topic paragraph, and it is a bit of a shocker:
Ramsden, of the National Institutes of Health, unearthed raw data from a 40-year-old study, which challenges the dogma that eating vegetable fats instead of animal fats is good for the heart. The study, the largest gold-standard experiment testing that idea, found the opposite, Ramsden and his colleagues reported on Tuesday in BMJ (formerly the British Medical Journal).
This doesn’t resolve any issues, but certain doctrines and beliefs are now on a lot less firm ground, including the putative benefits of choosing polyunsaturated vegetable fats over animal fats, and any causal link between animal fat intake and heart attacks.
Analyzing the reams of old records, Ramsden and his team found, in line with the “diet-heart hypothesis,” that substituting vegetable oils lowered total blood cholesterol levels, by an average of 14 percent.
But that lowered cholesterol did not help people live longer. Instead, the lower cholesterol fell, the higher the risk of dying: 22 percent higher for every 30-point fall. Nor did the corn-oil group have less atherosclerosis or fewer heart attacks.
The article also talks about how important findings from several studies were never published and abut the fact that a lot of the studies that have been published were observational studies (generally a methodologically lower quality type of study)