Extensive research in experimental animals has been able to demonstrate how lipids (fat deposits) can leave the bloodstream and enter the artery wall within 24 hours. The atherosclerosis produced in these animals becomes indistinguishable from the atherosclerosis seen in human arteries. What is known and what is important is that there is a definite ratio or relation between the amount of fats in the blood stream and in the artery wall, and this is surprisingly predictable in most cases. Also, the relationship of the fats in the artery wall itself is very close to that in the bloodstream. This direct relationship between the two seems to be in fairly constant balance.
The artery wall consists of three different layers. If the reader can picture a garden hose as representing the artery, it presents an innermost layer called the intima, a middle layer called the media, and an outer layer called the serosa.
The fats circulating in the blood stream are of course closest to the innermost layer of the artery, with which they are in direct contact. When conditions are right for atherosclerosis, the fats attach themselves and enter the inner or intima layer of the artery. A kind of wart or excrescence on the artery is then formed, called a plaque of lat. When the plaque grows larger, it encroaches upon the passageway of the artery. As it grows larger and larger, it may finally block or obstruct it partly or completely. When this clogging or obstruction of the artery takes place in the vital coronary arteries of the heart, then a coronary thrombosis or heart attack assails the victim. If the blockage from these fatty or atheromatous plaques occurs in the brain, then a stroke strikes down the victim.
However, if the artery is only partly blocked by this accumulation of fatty plaques, then the vital organs supplied by the arteries suffer from a lack of the necessary amount of blood and nutriments contained in it to sustain normal function and health.
Along with the fatty deposits of cholesterol, fatty acids, neutral fats, etc., which make up these atheromatous plaques, calcium and other minerals are also deposited. These make the artery feel hard, giving rise to the term commonly in use - "hardening of the arteries." Actually we see a softening of the arteries which takes place first because of these fatty deposits.
It is often noticed in many individuals that this free fat will be floating in the blood stream for hours after a meal containing fat has been eaten. The blood is then called lipemic, which means loaded with fats. When these fats are easily visible to the naked eye, scientists speak of such neutral fats as chylo-microns. These fats in the blood are regarded by many scientists to be as dangerous as is cholesterol, in entering the artery wall.
A great proportion of these fats in the blood are combined with proteins, called lipoproteins, which also have been the subject of research by many investigators. Scientists have only recently discovered by new tools of investigation that in these lipoproteins two separate portions can be measured: the alpha and the beta-lipoproteins. The first have been shown to be protective against the development of atherosclerosis. They are found predominating in infants, children, and young women who have no evidence of atherosclerosis.
On the other hand, the beta-lipoproteins have been found universally in excessive amounts in most cases of active athero-sclerosis and so are called atherosclerosis producers or "atherogenic." The protective alpha-lipoproteins are spoken of as "anti-atherogenic."
The problem of preventing atherosclerosis and its human ravages is the search for ways of increasing the protective alpha-lipoproteins. There are protective substances, such as lecithin, that can be used against the development of atherosclerosis.
One of the greatest factors influential in the current epidemic of heart attacks has unquestionably been the startling increase in fat intake. In the United States alone, the fat content of our diet has just about doubled in recent times. Where fat formerly constituted some 15 to 20 per cent of our meals 50 years ago, it now has jumped to 30 and 40 per cent or more.
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