LDL Is Not The Bad Guy
The idea that LDL is the 'bad' cholesterol is pivotal to the entire approach of mainstream nutrition. If this falls, the whole thing collapses. And it is falling.
The 'diet/heart' hypothesis first promoted by Ancel Keys is the lynchpin of the Dietary Guidelines. It runs right through our nutrition textbook - saturated fats are bad because they cause heart disease. The argument rests on these claims -
Eating fat raises blood cholesterol
High blood cholesterol leads to narrowing of the arteries
Supporters of this theory have been attempting to confirm it for half a century, and have failed completely. Every major study they've conducted has ended in disappointment. Nevertheless, they have persisted, to the point where this is unquestioned dogma within the mainstream.
Under pressure, they have shifted the goal posts over time. It used to be all cholesterol that was bad for you, but when it was found out that there is a direct relation between HDL and a REDUCED risk of heart disease, the focus shifted on to LDL.
LDL is a more plausible candidate as the bad guy as it is found in the fatty plaques that line damaged arteries.
Nevertheless, mounting evidence exists that lower levels of LDL in the blood are more likely to shorten your life than higher ones. So you may avoid a heart attack, but you will die of something else.
So do you want your LDL to be up or down ? The picture is confused. However, there are alternative explanations for what is going on that can resolve this apparent contradiction, and these are gaining momentum.
The question revolves around association versus causation and reverse causation. LDL may well be present - associated - with atherosclerosis, damaged arteries, but it does not follow that it is therefore the cause, in fact it might be the opposite. Damaged arteries, inflammation, is what leads to higher LDL and its presence in the plaques, LDL may actually be a good guy, part of the body's immune response to the presence of disease.
A second issue arises from a better understanding of the mechanisms involved in plaque formation. It turns out that the LDL found in plaques is itself damaged, it has been oxidised. Oxidation is a product of inflammation, and this has led to an alternative theory of heart disease, namely that is a disease of inflammation. The most likely culprit of this inflammation are the polyunsaturated omega 6 fats found in vegetable seed oils, the so-called 'healthy fats' in the standard diet. These industrial products have never been part of the human diet before the last 100 years and their adoption as popular cooking oils tracks the increase in heart disease extremely closely.
Further cracks in the mainstream position have appeared. It is not necessarily the case that LDL is associated with heart attacks, there is plenty of evidence showing the opposite. Likewise the relationship between dietary cholesterol and what's in your blood may actually be an inverse one - the more you eat the less your liver makes and introduces to the bloodstream (see Dave Feldman explaining this here). This is consistent with a view that the function of the VLDL particles, which later become LDL ones, is to collect fat from the body's tissues, so a higher LDL score means you are burning fat, good news if weight loss is your goal. This only applies if you avoid carbs however, because of the role insulin plays, carbs mess everything up.
The 'diet/heart hypothesis' is a tottering edifice. It is still dominant, partly through inertia, also because the implications of its falling are radical. Everything in the nutrition space hinges on this question. This is why the study shown in the picture alongside this post is so significant, it is the most highly downloaded study on the Taylor and Francis site, with more than 100,000 views so far. The study is free, so take a look for yourself https://www.tandfonline.com/doi/full/10.1080/17512433.2018.1519391