As a result of recent research, the following picture of cholesterol and health risk is emerging.
Cholesterol is an oil and must be packaged within a complex particle called a lipoprotein, in order to enable it to be transported within, blood which is water based.
Cholesterol leaves the liver in a lipoprotein carrier known as VLDL (very low density lipoprotein) which is a relatively large particle usually containing cholesterol and triglycerides. As this carrier lipoprotein deposits cholesterol at each site around the body it shrinks, eventually becoming the size to be referred to as LDL.
When it has delivered its load of cholesterol, it returns to the liver and the process begins again. Cholesterol is critical for many functions in the body including functioning of your immune system, your nerves and your brain. Without it you will die. The HDL lipoprotein carries unused cholesterol from body tissues back to the liver.
The surface of the LDL lipoprotein has a receptor protein known as Apo B-100 which is like a key and identifies the lipoprotein to each place it is required, plus to the liver on its return. If this receptor should become damaged in any way, then the particle is not recognized by any of the locations and it becomes an orphan particle.
There are a number of ways this receptor can be damaged with glycation being one of these and another is by oxidation. Excess sugar in the blood can drive glycation and oxidative stress caused by oxidized oils in the diet, can drive this oxidation of the LDL particle and receptor.
The oxidized LDL becomes an orphan and eventually arrives in the arterial wall.
Professor Vladimir Subbotin suggests that oxidized LDL cholesterol gets into your artery wall not from inside the artery, through the endothelial layer as usually proposed, but by being deposited there from the outside by the blood that supplies the artery walls. His argument is very compelling and if true, indicates a sequence whereby an offending factor causes the initial thickening of arterial walls in the intima, just behind the endothelial layer which then due to the thickness, calls for an additional blood supply which is responded by blood vessels (vasa vasorum) growing into the intima layer from which time oxidized LDL particles can accumulate at that point.
A key driver for this view is that early stage oxidized LDL particle deposition occur at the intima / media junction rather than behind the endothelial layer and at these sites the blood vessels have already grown to supply the area with blood.
The damage in the artery walls then form plaques. It has now been found that higher levels of LDL can assist in regression of these plaques, whereas lower levels of LDL assist plaque progression. These plaques are the beginning of atherosclerosis (arterial blockages) eventually resulting in coronary artery disease.
Where do oxidized oils come from? The most prevalent source of oxidized oils is oxidized seed oils (PUFA, Polyunsaturated Fatty Acids) in the diet. It is near impossible for seed oils not to be oxidized and oxidative stress in the body has been consistently measured following vegetable oil consumption.
Saturated fats have a molecular structure that renders them very stable and unlikely to become oxidized, which means that they do not contribute to this oxidative stress. We have a simple measure of oxidative stress which is the ratio of HDL to triglycerides in your blood. Triglyceride level divided by HDL level will produce a result which we want to see under 1.5 or better still close to 1.0.
Apparently research has identified that the Vegan diet will reduce HDL and raise Triglycerides which indicates an increase in oxidative stress on this diet. While researches often cite the reduction in LDL that this causes as good, it is now believed that while the overall LDL has decreased, the level of oxidized LDL has increased significantly.
So in summary, LDL itself is not a driver of atherosclerosis and may not deserve its label as bad cholesterol. Only oxidized LDL progresses the formation of plaques in arteries and this is primarily driven by consumption of oxidized oils with the most prevalent being being polyunsaturated seed oils, also known as vegetable oils.
Incidentally low cholesterol levels are correlated with higher rates of overall mortality (Not lower). Particularly in people over 60, higher cholesterol is more healthy. This is opposite to conventional advice. UK Dr. Zoe Harcombe PhD. has produced some great plots by gender, of mortality per 100,000 people vs cholesterol levels using WHO data from 192 countries, which clearly show this correlation.
George Elder, Author "Take Back Your Health", Amazon here.