The biggest problem in assessing the effects of cholesterol is that cholesterol appears to be beneficial in the subgroup of people who have not had arterial scarring, calcium buildup, a history of smoking or who engage in very high levels of aerobic exercise like running more than 40 K per week. Cholesterol can’t directly cause atherosclerosis because it can not carry oxidative species to the arterial linings, but if the oxidative damage occurs then excess cholesterol can stick to the lesions and calcium deposits and “backfire”, though the main reason that the body sends cholesterol to the blood vessel linings is to reinforce and heal damaged arterial linings. When the damage gets chronic, cholesterol produced by the body goes up, so high cholesterol is an early mechanism to protect atherosclerosis but eventually becomes similar to putting too many band aids on a wound.
I have a problem with meta studies because in my opinion, most of the original cholesterol studies were based on an assumption that dietary cholesterol raised blood cholesterol and that blood cholesterol caused atherosclerosis, so we have a huge body of original biased studies, many of which were funded by corn, soy and canola producers to show that corn, soy and canola lowered blood cholesterol (which they DO) and that blood cholesterol raised mortality (which it doesn’t on balance). The fact that corn, soy and canola oils “artificially” reduce blood cholesterol levels shows up in the data as saturated fat RAISING cholesterol levels because people who eat more corn, soy and canola have low, and sometimes harmfully low cholesterol levels. https://www.ncbi.nlm.nih.gov/pubmed/29551407 though if you already have massive endothelial lesions, it might help because you can prevent the cholesterol backfire mechanism.
I don’t have time to delve deeper now, but I will also mention that regarding earlier studies and meta studies, another confounding factor was that saturated fat diets used to mean high trans fat diets, but natural saturated fatty acids are not trans (with a few oddball exceptions).
So lastly for now, a couple of oddball relationships that confound the data. Many studies have shown that high circulating ala levels correlate to health. These studies often suggest that it is the cholesterol lowering effect or a heart protective mechanism, however it is well established that when someone has chronic infections, their body gets depleted of ala (omega-6). So we have a situation where sick people’s bodies naturally make cholesterol and get depleted of omega-6 in the process of fighting illnesses. It makes it very necessary to separate people into healthy and unhealthy subgroups. If you are already healthy, don’t have arterial scarring or risk factors and are not fighting chronic infections, high blood cholesterol correlates to higher lifespan up to well over 200, as does a lower intake of omega 6. If you are sick and diseased, things change.