In order to do any job in a proper way one needs knowledge as to how to do it. Similar is the case with protection of health. One must know the factors that cause narrow. ing of the coronary artery and try to eliminate them. The major factors that lead to premature narrowing of coronary artery are:
- High blood pressure
- Fat and high cholesterol level in blood
- Smoking and excessive drinking.
Fats: Fats are made up of fatty acids and glycerol. We get fats from ghee, butter, vegetable oils and hydrogenated vegetable oil. It is also present in some degree in milk, meat, eggs, lentils, cereals, nuts, etc. After the food we eat undergoes metabolic process, fats are digested in intestine and absorbed into blood circulation. Some of them provide calori to the body for performing various functions and some are stored in different parts of the body. That is why we find some people too fat.
After absorption, the fats move about in the body either as tiny particles or combine with proteins to become soluble in blood stream.
The tiny particles, about 1 micron in size nearly of neutral fat in the blood are called chylomicrons (chyle is the white milky product formed as a result of digestion of fats in the food). A chylomicron is about one-seventh the size of a red blood cell.
And when combined with different proteins, the fats form even smaller globules. They are called lipoproteins.
These globules are made up of a core which JS a mixture of fats and cholesterol. Covering the core is a layer of phospholipids—a kind of fat which also contains phosphoric acid and protein groups. These globules are covered by an extremely thin layer of proteins. In these globules, fat dissolves the cholesterol which otherwise cannot be transported by itself as it is insoluble in the blood as such. And as pure fatty globules stick together, a layer of phospholipids and proteins removes this tendency.
If the fats and cholesterol are to be carried by the blood to the tissues, these four substances, viz., fats, cholesterol, phospholipids and proteins must always remain linked together. The thicker the protective coat of phospholipids, the more stable the globules. The smallest of the lipoprotein globules has the heaviest coat and hence is the most stable.
Cholesterol is also a type of fat found in animals and animal products like milk, meat, brain, eggs, etc. But it is absent in vegetable and its products. Since it is insoluble in blood, it is transported alongwith other things in different lipoprotein globules.
It is, however, an essential constituent of the body, used in tissues and activities. It acts as an excellent insulator in brain and nervous tissues. Brain, in particular, has enoUgh of it so that electrical impulses travel unhindered. If it is not there, electrical impulses travelling in the nerves would get short-circuited. It is also the source of material for the manufacture of male and female sex hormones. The yellow part of the egg has a high concentration of it.
From the diet that we take daily, we get about 200 to 800 mg. of it. It depends on the animal fat we take. Apart from that, cholesterol is also manufactured in the body by the liver from carbohydrates, proteins and fats we take. But that is a smaller quantity—l.5 to 2 gram. Bile juice and fats help in the absortion of cholesterol in the intestine. Thereafter it enters the blood through lipoproteins particles, the carrier molecules. It is low-density lipoprotein that transport fats from liver to body cells and high-density lipoproteins return fats to the liver.
Cholesterol is oxidised to carbon dioxide by many tissues and the liver. Some of it is converted into steroid hormones and the major portion into bile acids.
It is the liver which is chiefly concerned with its manufacture, store and destruction. It largely controls the level of blood cholesterol by regulatory mechanisms between the absorption and synthesis of cholesterol on the one hand, and the metabolism and excretion on the other.
It has been found that the amount of cholesterol in the food has a significant effect upon Che blood cholesterol level. Doctors generally recommend that the total blood cholesterol level should be less than 200 mg/dl. And LDL cholesterol should be less than 130 mg/dl. HDL cholesterol should be greater than 35 mg/dl and triglyceride levels less than 150 mg/dl. The intake of fat in the diet also exerts a strong influence on blood cholesterol. Studies have shown a tendency to a fall in blood cholesterol if there is fall in the intake of fat in the diet.
Risk factor: The ratio of total cholesterol to high-density lipoprotein and the ratio of low-density lipoprotein and HDL show whether cholesterol is being deposited into tissues or broken down and excreted. The total cholesterol and HDL ratio should be less than 4.5 and that of LDL and HDL less than 2.5.
By lowering LDL cholesterol and raising HDL levels, the risk of heart disease can be greatly lowered. Various studies have shown that the high level of cholesterol has much to do with coronary heart disease and if the cholesterol level is low, the cases of heart coronary diseases are also low.
High cholesterol level and heart disease
A high level of cholesterol in blood, particularly in the form of LDL globules—which are more unstable so that the cholesterol comes apart easily—leads to its deposition in blood vessel walls and irritate it severely.
From what has been written above, we can infer that dietary cholesterol intake from 0 to 600 mg/day is closely related to plasma cholesterol levels and saturated fatty acids raise blood cholesterol levels while polyunsaturated fatty acids reduce them and low-cholesterol, low saturated fat diets lower blood cholesterol levels.
High cholesterol and high triglycerides levels in the blood are risk factors for atherosclerosis. In adults less than 55 years of age, a cholesterol concentration greater than 200 mg/ 100 ml or a triglyceride concentration greater than 200 mg/ 100 ml, clearly indicates high fat content in the blood. In many cases, high cholesterol level is due to hereditary factors. In such cases there is defect in the receptor protein for low-density lipoprotein in liver. LDL receptor normally removes cholesterol from blood. But in the above cases liver does not get the message to stop making cholesterol.