The cholesterol is a soft yellow-white, waxy element, present in the wall surrounding every cell of body. It is used by the body in making other elements in the body. It is essential for the survival of human life. It is part and parcel of muscles, fat tissues, brain and nerves. It is vital for proper brain function, stress control, concentration, memory and for guarding against exhaustion. It is active in metabolic processes of blood plasma, liver and intestines.
It is an important part of a healthy body because it is used to form certain hormones and necessary tissues. The problem occurs when you have too much of cholesterol in your body. Cholesterol comes from two sources. It is produced in your body, mostly in the liver, and sources. It is produced in your body, mostly in the liver, and is found in dairy products and non-vegetarian foods. 20%-30% comes from the food we eat. The most concentrated sources of cholesterol are egg yolk, meat and whole milk dairy products.
In fact, your body needs small amount of cholesterol to function normally. your blood carries cholesterol throughout your body. That why its called blood cholesterol.
Cholesterol can not dissolve in blood; it travels through blood vessels, attached to special carriers called lipoproteins.
Lipoproteins are large globular particles which transport cholesterol and triglycerides in plasma as components. Lipoproteins also contain other lipids e.g. phospholipids and transport of lipoproteins.
Chylomicrons : In the liver, cholesterol combines with water soluble substances called apolipoproteins and phospholipids to form chylomicrons. These chylomicrons are a form of complex particles called lipoproteins, which is, fats combined with proteins. These are the largest of the lipoprotein particles and formed in intestinal mucosal cells. Their function is to transport lipids from intestine to lymphatics and plasma by constituting the form in which dietary lipids are located.
Very low density lipoprotein (VLDL) : These are produced by the liver. They serve as the major transport form for endogenously synthesised triglycerides from the liver. They have very low density and weight as per the name. Some of it is used for energy and rest is stored in the fat deposits. A good portion of it is returned to liver for excretion. It is converted into LDL.
The reason of increase in plasma concentrations of triglycerides rich lipoproteins are :
- Due to increase in the rate of hepatic production of VLDL particles, or
- Due to decrease in the rate of removal of VLDL and chylomicrons, from plasma.
Most studies have shown that raised triglycerides is a marker for increased risk of coronary heart disease.
High Density Lipoprotein (HDL) : These are derived from direct hepatic secretion and during intravascular lipolysis of chylomicron particles. There is inverse correlation between plasma concentrations of HDL cholesterol and atherosclerosis. High level of HDL protects against the development of atherosclerosis by enhancing removal of cholesterol from tissues. They contain great amount of proteins and a small amount of cholesterol.
It is formed in the liver and the walls of the small intestine. While maturing in the blood stream, it gets cholesterol from the adjoining tissues. In circulation it reaches back to the liver, from where the cholesterol is excreted in the bile. In this process it cleanses the body and helps in removal of excessive cholesterol.
Low Density Lipoprotein (LDL) : It is an end product of VLDL metabolism. It is derived from intravascular catabolism of VLDL. LDLs carry approximately 60% to 80% of the body cholesterol. It is the chief factor for causing calcareous and LDL desired level should be below 130 and if you are having any other cardiac risk factor it should be less then 100. A level above 160 puts you at high risk for suffering heart disease, heart attack or, indirectly, stroke. LDL constitutes the major portion of cholesterol in the body. The details about plasma lipoproteins are presented in Table below :
Dietary fats are biochemically known as triglycerides because every molecule of fats has one molecule of glycerol linked up with three molecules of fatty acids – same acid or three different acids.
Triglycerides are the major form in which fat occurs in nature. It comes from food and is also made in your body. Often elevated with cholesterol, they may be a risk factor for heart attack. It is good to reduce high triglycerides.
Triglycerides form the bulk of your body fat where they are stored for later use as energy. your diet is the primary source of triglycerides. Levels below 250 mg/dl are considered normal. Elevated Triglycerides role in increasing the risk of heart disease is not clear. However many people with elevated triglycerides also have high LDL or low HDL cholesterol levels.
Most people with triglycerides levels between 200-400 mg/dl have underlying disease or genetic disorders. The main therapy for them is to change their life style, control their body weight, eat low fat, low cholesterol diet, exercise regularly, stop smoking and reduce alcohol intake.
High triglyceride levels often accompany high total cholesterol levels. A large number of people with heart disease are shown to have high triglyceride levels.
At the same time, people with very high triglyceride levels can be free from atherosclerosis. So high triglycerides may not directly cause heart disease. Instead, they may merely accompany other problems, like diabetes that speed its development.
The levels of triglyceride are more high among people with diabetes, overweight, or kidney problems. Mostly triglycerides are found high especially in the presence of other abnormal risk factors.
- Hyper tiglycerides are more harmful with diabetes, obesity, dietary factor, alcoholism, and raised VLDL due to free fatty acids.
- Raised triglycerides can be cured by weight reduction, less of saturated fats, cure of diabetes hypothyroidism if present, avoidance of alcohol oral contraceptives. Clofibrate drug is given if necessary.
The lipoprotein is highly thrombogenic and antifibrinolytic, by virtue of its structural homology to plasminogen. It promotes early atherosclerosis. Its atherogenicity is 10-fold higher than LDL and 15-fold higher than total cholesterol.
If there is a family history of heart attacks, heart disease or high cholesterol, even children should be tested for genetically acquired high cholesterol level, which makes a child prone to heart disease at a tender age.
An inherited defect is likely in a child with a cholesterol level of 200 mg/dl or higher.
When the genetic risk is not present, the professional recommendation is to get the first cholesterol reading at the age of 20, and if it is normal, every five years thereafter.
It involves a simple blood test. Cholesterol is measured as mg/dl of blood. HDL S LDL cholesterol should also be checked.
The recommended guidelines to determine the risk for heart disease are based on blood levels of cholesterol and presence or absence of other risk factors.
Cholesterol levels tend to be about 5 to 7 milligrams higher in the winter months than in summer months. Cholesterol measurements are most accurate when the patient has been fasting for 12-14 hours before the blood sample is taken. The easiest way to do this is to have your blood drown in the morning before eating breakfast. It is better to give sample without venous compression.
High blood triglycerides also reduce HDL-cholesterol levels, and thus increase the risk of developing a heart attack.
The ratio of total cholesterol to the HDL-cholesterol is very important to identify the coronary risk in a patient. Ideally the ratio is as follows
Higher the ratio, greater are the chances of developing a heart attack.
A strong link has been established between TG levels and CHD, hence it is not just your LDL and HDL levels you must keep track of, but also your TG levels.
To understand better, the HDL is a good cholesterol, the LDL is a bad cholesterol, and the Triglyceride is a ugly cholesterol. The lipoprotein can be best described as deadly cholesterol.
Hyperlipoproteinaemia : It is a condition in which the concentrations of cholesterol and triglycerides – rich lipoproteins in plasma are elevated above normal levels. Such condition may be associated with disease like :
- Atherosclerosis of both coronary and peripheral arteries.
- Xanthomas in the skin and tendons.
- Acute pancreatitis
- Hypothyroidism, as a secondary cause.
ROLE OF CHOLESTEROL
Cholesterol is an important constituent of the body cell membrane. It is also a base from which steroid hormones are produced. The cholesterol is essential for proper functioning of the body cells. It is responsible for the formation of sex hormones and vitamin-D metabolism in the body.
As income levels rise, and lifestyles improve, there an increasing intake of rich foods. And rich foods, as we all know, are high on saturated fats. These, in turn, increase cholesterol levels in the blood, the optimum. Add to this an easy-going lifestyle, without minimum physical activity. Plus the stress and strain of modern living.
The end result is higher cholesterol levels, and the risks of heart attack and coronary disease. What is more, these risks are spreading to the younger are bracket, those below 40. Obviously, to lead a healthy life, cholesterol levels much be kept under constant check.
The study of cholesterol metabolism is still a subject of research. The discovery of receptors involved in this cholesterol metabolism, with differences in them, explains the reasons for member of a family to have different cholesterol levels even after consuming a same or similar diet.
Even a single meal high in fat and cholesterol may cause the body to release a hormone, Thromboxane which cause the arteries to constrict and the blood to clot faster. This is one reason why patients often get chest pain after eating a fatty meal and why so many of them end up in the Emergency after a rich feast.
A decade ago, the average Indian lived up to 53. Today our life span has increased to 63, and this is growing every year. People are living longer, becoming older and that is why heart diseases and cancer are becoming more known and also a problem. A very large section of our 1000 million population is ageing and the knowledge explosion has made them aware of these dangers. Diagnosis has also improved. That is why more and more cases are being recorded, treated and cured these days.
Every effort should be made to prevent serum cholesterol from being elevated above 150 mg/dl in high risk cases, and 200 mg/dl in normal individuals. If this level can be prevented from rising above 150 mg/dl, plaques are not laid down; if elevated, levels are lowered to 150 mg/dl, further plaques do not form and part of those present may vanish.
The LDL-C levels should be lowered and maintained below 100 mg/dl in patients with CAD.
The cholesterol level for a person is not a fixed value at all times. The common changes in diet, stress, time and weather make a difference in the cholesterol numbers.
The term lipid denotes cholesterol, and all of its types like HDL, LDL and triglycerides. The variation of 5 to 10% is seen in the area of laboratory testing. The change of posture from lying down to sitting up raises cholesterol due to increased protein in the blood. The cholesterol gets lowered if you have lost weight recently. The cholesterol is found 5 to 8% higher in winters. The cholesterol results get higher with tight tourniquet and hard squeezing of fingers during blood sample collection. It could be due to blood protein bound with cholesterol, gets squeezed and this extra protein in the blood sample cause false higher value. The persons with borderline values are advised to have three different tests from blood taken on three different days. The average of these will be a right result.
Use of oral contraceptives and pregnancy are known to increase blood cholesterol level in some women. Cholesterol increase during pregnancy, which could be up to 40% higher during last weeks, as compared to no pregnancy.
However, it returns to normal by about 20 weeks after child birth. The average blood cholesterol level in women prior to menopause is lower than that of men of same age. However, the average cholesterol level in women usually increase after menopause to a level higher than that of men. The cholesterol level gets raised with heart attack because of stressful condition. One needs to wait for about 3 months after the attack to get base level value.