Cholesterol, a vital part of the human diet, is essential for the production of testosterol, adrenal hormones, myelin, the lining of nerves and membranes of the brain. Considering all these vital functions, it's difficult to see how cholesterol could be responsible for heart disease. The amount of cholesterol formed by the liver is controlled according to the needs of the body. If dietary cholesterol is increased, a healthy liver responds by making less cholesterol for the needs of the body. But if the cholesterol in the diet is decreased, the liver makes more. In this way the body regulates how much cholesterol is produced for its needs.
The idea that cholesterol may be responsible for heart disease was first muted in 1908, when it was observed that patients with arteriosclerosis tended to come from the wealthy classes, Such people had a diet high in meat, butter, eggs and milk, in contrast to the diet of poorer classes.Then several Russians fed a high animal protein diet to rabbits, which are ordinarily vegetarian, and found that after several months the animals had developed hardening and plaques of the arteries similar to those found in patients with arteriosclerosis. Although it was first thought that high protein from the meat and dairy produce was responsible (the plaques in the rabbits' arteries contained fat and cholesterol crystals) and so cholesterol took the blame.
In animal experiments, a group of cholesterol compounds that contain extra oxygen atoms were found to produce arteriosclerosis (Br J Exper Path, 1965; 46: 549-53). But highly purified cholesterol, free of all traces of oxycholesterol and protected from the oxygen of air, does not injure the arteries of animals (Arch Pathol and Labn Med, 1976; 100: 565-72). It is highly unlikely that the Russians took elaborate precautions to prevent the exposure of the cholesterol they were using from oxygen. All they were demonstrating was that oxycholesterol contaminants, rather than cholesterol itself, were producing arteriosclerosis in their experimental animals.
These highly damaging oxycholesterols are found in foods in which cholesterol is subjected to heating and exposure to oxygen during either food processing, cooking or preservation. Such foods include dried egg yolk, dried milk powder and foods fried in heated oils. The oxycholesterol in these foods is absorbed into the blood after digestion and then becomes concentrated in low density lipoprotein in the blood. When lipoproteins are taken up by arterial wall cells, the cholesterol oxides that are released damage artery wall cells and tissues leading to arteriosclerosis.