A Stealthy and Silent Killer

One of the major developments in the medical field several years ago was the successful research done by the National Heart, Lung and Blood Institute, United States, which, for the first time, scientifically established beyond doubt that there was a definite correlation between the level of cholesterol in the blood and the incidence of heart attacks and other related diseases.

Cholesterol was first purified as a whitish yellow substance with a soap-like consistency in the year 1769 by the French chemist Poulletier de la Salle. Almost 80 per cent of the cholesterol in the human body is generated by the liver. The remaining 20 per cent is found in the food that one consumes.

Cholesterol is useful to the body in many ways. It is one of the constituents of the bile, and one of the ingredients of the outer sheath of cells. It is part of the protective covering of nerves, and also of the sex hormones—estrogen and androgen.

However, excessive cholesterol particularly in the food one consumes, could prove ultimately dangerous by leading to a condition known as ‘atherosclerosis’. Doctors had become concerned about the role of cholesterol when they had found deposits in the damaged arteries of heart attack victims. It was in 1913 that a Russian pathologist had concluded that a diet rich in cholesterol could lead to deposits being formed in the arteries.

Doctors and scientists thereafter began to study the food habits of various people and their consequent vulnerability to heart attacks. Their studies revealed that Finns and Americans, who take a diet rich in fats, have the highest level of cholesterol in their blood, whereas others such as the Japanese, who take comparatively low fat diet, have a very low level of cholesterol in their blood. In addition it was noticed that Japanese who had migrated to the West and had resorted to taking fatty diet had registered a high increase in cholesterol levels.

With a view to establishing scientifically a direct link between cholesterol and heart attacks, a massive research programme was taken up in 1973 by studying a group of 3,806 men. Half the group was given a cholesterol-reducing drug called cholestyramine. The other half was given the same food, but without the drug, i.e. a placebo. The people who did not take the drug were not aware that the drug was not administered. At the end of the study the group that had been put on the drug registered comparatively lower cholesterol levels and a much lower rate of death due to heart attacks. The study of cholesterol also drew the attention of scientists to the study of low-density lipo-proteins (LDL) and high-density lipo-proteins (HDL). LDL keeps circulating in the body and is responsible for conveying fats/cholesterol to the cells. On the other hand, HDL performs the task of removing cholesterol from the blood. Thus, a high concentration of LDL is thought to increase the risk of heart attack, whereas a high concentration of HDL is thought to lower the risk.

Doctors, at the same time, were able to obtain several clues regarding the factors which influence cholesterol levels and thus heart attacks. There is positive evidence to conclude that certain foods such as eggs, cheese, saturated fats, bacon, butter, beef, whole milk, oil, and any food of animal origin seem to contribute to an increase in LDL levels. On the contrary, poly-unsaturated oils such as palm flower oil and sunflower oil lower the level of LDL, though coconut oil contributes to an increase in the level of LDL.

The quantum of fibre in the food seems to play an important role in keeping the level of LDL under check. Hence, vegetables with good fibre content would appear to inhibit the formation of LDL. Fibre also seems to increase the HDL level.

Lifestyles of people also appear to contribute to the fluctuation in levels of cholesterol. Regular exercise, for example, can successfully raise the level of protective HDL. It was also believed in some quarters that alcohol in moderate quantities could raise the HDL level but because of the controversial nature of such opinions and also because of the other obviously undesirable effects of alcohol, it is felt that the possible damage to the system outweighs the benefits. Stress is thought to increase cholesterol and worry situations contribute to peak cholesterol levels.

The unfortunate and dangerous aspect of cholesterol is that while it is getting deposited in a slow and imperceptible manner in the arteries, the person concerned is totally unaware of what is taking place in his body. By the time the cholesterol gets firmly entrenched like rust in an iron pipe or garbage in an underground sewer, it is too late to do anything. If this deposit causes obstruction to the flow of blood in the coronary artery, it would result in a heart attack. If it obstructs flow in a carotid artery, it would lead to a cerebral stroke.

It would appear that at birth almost everybody has the same low level of cholesterol (50 mg per decilitre of blood). As a person ages the amount of cholesterol in the blood doubles towards adulthood. Similarly, boys and girls have the same cholesterol to begin with. But during puberty boys experience a 25 per cent drop in HDL and a corresponding rise in LDL. These factors would explain the reasons why women have fewer heart attacks as compared to men.

Another factor which seems to play an important part in this context is the role of LDL receptors which sit on the surface of cells and remove cholesterol from the blood. People who were deficient in LDL receptors are comparatively more vulnerable to heart attacks.

How important LDL receptors are can be assessed by the fact that the members of a certain tribe of Indians in the United States are not exposed to an increased risk of heart attacks, even though their food is rich in fat. Scientists speculate that these Indians might be having a high concentration of LDL receptors in their system. This kind of inherent genetic protection is probably available for some people in many societies.This factor would explain why some people who lead a carefree life, consuming fatty foods, smoking cigarettes and generally not taking any special precautions to protect their health continue to live to a ripe old age. But perhaps, such genetic protection cannot be taken for granted by everybody. The wise person is one who leads a stress-free life, avoids smoking, consumes a balanced diet devoid of fatty foods but has a high fibre content and performs exercise regularly.

A heart attack occurs whenever there is interruption in the supply of blood, rich in oxygen, to the heart muscle due to an obstruction in a coronary artery. The blockage or obstruction itself can take place due to one of the following three reasons: the accumulation of fatty deposits of cholesterol or plaque in the artery, or the occurrence of spasms in the artery or the formation of blood clots.

Modern-day doctors with advanced surgical techniques can insert a catheter having a small balloon at its end into an affected artery. By inflating this balloon the plaque is flattened against the arterial walls thus creating more space to enable the blood to flow easily.

Another advanced technique which is laser angioplasty. In this technique also, a catheter is inserted into an artery but a laser at the end of the catheter destroys the plaque restoring the blood flow. Scientists have observed that clots generally have a tendency to appear at places where the cholesterol deposits make the artery narrow.

Doctors can use drugs such as streptokinase which have the power to dissolve clots. Streptokinase can be inserted into an artery by means of a catheter or even given intravenously. But the main drawback in using the latter method is that here is a possibility of haemorrhage occurring due to the entire clotting mechanism going haywire.

Doctors are also hopeful of achieving success in tackling heart attacks with preparations such as t-PA (tissue plasminogen activator) which is basically an enzyme the body itself produces and which also has the ability to dissolve clots. Preliminary experiments indicated that this enzyme has the ability to minimize the damage during a heart attack. Its full potential is yet to be studied.

Yet another nasty complication is a spasm which makes an artery contract, thus inhibiting the flow of blood. Doctors tackle such conditions with the use of drugs called calcium channel blockers. These drugs help in increasing the supply of blood to the heart by preventing contraction of the artery, and also by reducing the heart’s demand for oxygen.

When plaque gets deposited in a carotid artery which carries blood to the head, a cerebral stroke can occur just as the plaque present in a coronary artery causes a heart attack. An important tool which is being developed currently for doctors to locate plaque in carotid artery is the ultrasound technique.

In the preceding technique sound waves are aimed at a plaque deposit in the artery and get reflected back, to provide, on a screen, a fine picture of the deposit. The ultrasound technique cannot be used to draw a picture of plaque in the heart because of the heart’s rapid movement and also because of the obstruction caused by the breast bone. This technique can enable doctors to ascertain the presence of plaque in a carotid artery long before trouble actually develops.

Another similar technique is the Doppler ultrasound which enables doctors to measure the velocity of blood. When blood rushes through a narrow artery, its velocity increases. However, unless the velocity is significant enough as in the case of advanced arteriosclerosis, the Doppler ultrasound may not yield useful results.

To sum up, there is a new awareness among scientists and doctors as well as laymen about the dangers of cholesterol. In his fight against disease, man has been able for the first time to successfully identify, in a scientific manner, the factors that cause a heart attack. A proper mixture of low cholesterol food, a tension-free life, regular exercise and cholesterol-reducing drugs, if warranted, would go a long way in eliminating this scourge from the list of the worst killers known to medical science.

Statins are drugs that can lower your cholesterol. They work by blocking a substance your body needs to make cholesterol. Lowering cholesterol isn’t the only benefit associated with statins. These medications have also been linked to a lower risk of heart disease and stroke.

Indeed, some scientists speculate that even surgical techniques like bypass surgery may one day become obsolete if the above principles are followed to the letter.

The following chart gives the cholesterol content of different food products

KILLERS IN THE KITCHEN