Cholesterol is a white crystalline substance, C27H45OH, found in animal tissues and various foods, that is normally synthesized by the liver and is important as a constituent of cell membranes and a precursor to steroid hormones. Its level in the bloodstream can influence the pathogenesis of certain conditions, such as the development of atherosclerotic plaque and coronary artery disease.
holesterol is the most common type of steroid in the body. Cholesterol is essential in the formation of Bile acid, vitamin D, Progesterone and Estrogens. Cholesterol is also necessary to the normal permeability and function of cell membranes, the membranes that surround cells.
Cholesterol, like oil, cannot dissolve in the blood unless it is combined with special proteins called lipoproteins. (Without combining with lipoproteins, cholesterol in the blood will turn into a solid substance.) The cholesterol that is secreted by the liver into the blood is combined either with very low-density lipoproteins (VLDL) or high-density lipoproteins (HDL). VLDL cholesterol is then metabolized in the bloodstream to produce LDL cholesterol.
The two types of Cholesterol:
Cholesterol is carried in the bloodstream as lipoproteins. Low-density lipoprotein (LDL) cholesterol is the "bad" cholesterol because elevated LDL levels are associated with an increased risk of coronary artery (heart) disease. LDL-C Low-density-lipoprotein cholesterol carries the largest amount of cholesterol in the blood and is responsible for depositing cholesterol in the artery walls. An elevated LDL-C level is associated with a greater risk of heart disease.
By now you should have heard about your total and low-density lipoprotein (LDL) cholesterol levels and whether they are normal or high, and about the risks associated with your blood lipid and lipoprotein levels. Conversely, high-density lipoprotein (HDL) cholesterol is the "good" cholesterol since high HDL levels are associated with less coronary disease.
The averages of cholesterol:
This table presents the normal averages of LDL and HDL cholesterol in the blood in case of risk or without risk factor:
|
Total cholesterol |
Less or equal to 2,30 g/l |
|
Total cholesterol |
Less or equal to 2 g/l |
|
Cholesterol HDL |
Greater or equal to 0,55 g/l |
|
Cholesterol LDL |
Less or equal to 1,50 g/l |
|
Cholesterol LDL |
|
Some physicians may ask for a specific dosage of LDL and HDL cholesterol which is the following:
(Total cholesterol / HDL) Less or equal to 4,5
The effects of Cholesterol on blood circulation and cardio functioning:
Blood cholesterol levels in both men and women begin to go up around age 20. Women before menopause have levels that are lower than men of the same age. After menopause, a women's LDL-cholesterol level goes up--and so her risk for heart disease increases. For both men and women, heart disease is the number one cause of death.
Arteries that supply blood and oxygen to the heart muscles are called coronary arteries. LDL lipoprotein deposits cholesterol on the artery walls, causing the formation of a hard, thick substance called cholesterol plaque. Over time, cholesterol plaque causes thickening of the artery walls and narrowing of the arteries, a process called atherosclerosis. When coronary arteries are narrowed by atherosclerosis, they are incapable of supplying enough blood and oxygen to the heart muscle during exertion. Lack of oxygen (ischemia) to the heart muscle causes chest pain, also formation of a blood clot in the artery can clause complete blockage of the artery, leading to death of heart muscle (heart attack).
One type of heart disease is called coronary heart disease (CHD), which is caused by cholesterol. CHD results in narrowing of coronary arteries. In time, the inadequate supply of oxygen-rich blood and nutrients damages the heart muscle and can lead to heart attack and possibly to death.
Atherosclerotic disease of coronary arteries (coronary heart disease) is the most common cause of death. HDL is called the "good cholesterol" because HDL cholesterol particles prevent atherosclerosis by extracting cholesterol from the artery walls and disposing of them through the liver.
The causes of high cholesterol:
The cholesterol in a person's blood originates from three major sources which are liver production, dietary intake and heredity.
The bad functioning of liver: The liver not only manufactures and secretes LDL cholesterol into the blood; it also removes LDL cholesterol from the blood. To remove LDL cholesterol from the blood, the liver relies on special proteins called LDL receptors that are normally present on the surface of liver cells. A high number of active LDL receptors on the liver surfaces is associated with the rapid removal of LDL cholesterol from the blood and low blood LDL cholesterol levels. A deficiency of LDL receptors is associated with high LDL cholesterol blood levels.
Overweight: Excess weight tends to increase you LDL (bad) cholesterol level. If you are overweight and have high cholesterol levels, losing weight may help you lower it. Weight loss also helps to lower triglyceride levels as well as raise HDL (good) cholesterol levels. Another "side effect" of being overweight is a high risk of heart disease, which is a direct result of low HDL levels and high triglyceride levels.
Bad diet: Diets that are high in saturated fats and cholesterol decrease the LDL receptor activity in the liver, thereby raising the levels of LDL cholesterol in the blood. Dietary cholesterol comes mainly from meat, poultry, fish, and dairy products. Organ meats, such as liver, are especially high in cholesterol content, while foods of plant origin contain no cholesterol. After a meal, cholesterol is absorbed by the intestines into the blood circulation and is then packaged inside a protein coat.
Heredity: Heredity has a significant influence on a patient's LDL, HDL and total cholesterol levels. For example, familial hypercholesterolemia (FH) is a common inherited disorder whose victims have a diminished number or nonexistent LDL receptors on the surface of liver cells.
How to avoid high cholesterol:
In the past 10 years, clinical trials have conclusively demonstrated that lowering LDL cholesterol reduces heart attacks and saves lives. Eating saturated fat can raise cholesterol levels in the blood. Saturated fat is found in animal foods and some plant foods.
Cholesterol comes from animal products. Many foods contain both saturated fat and cholesterol. Food labels contain information about fat and cholesterol content. It is recommended that you:
- Avoid saturated fat and oils, such as butter, bacon drippings, lard, palm oil, and coconut oil. Palm and coconut oils are often found in processed foods. Replace these with olive oil.
- Limit the use of fatty acids or partially hydrogenated vegetable oils, such as those found in hard margarines, snack crackers, cookies, chips, and shortenings. Hydrogenation is a process that makes the fat solid or semisolid.
- Limit fatty meats such as corned beef, pastrami, ribs, steak, ground meat, frankfurters, sausage, bacon, and processed meats like bologna. Limit high-cholesterol organ meats (liver and kidney) and egg yolks. Replace with skinless chicken or turkey, lean beef, veal, pork, lamb, fish, and meatless main dishes including beans, peas, pasta, or rice.
- Limit servings of meat, poultry, and fish to 2 oz (56.7 g) to 3 oz (85.1 g) (a serving is about the size of a deck of playing cards), twice a day, or no more than 5 oz (141.8 g) per day.
- Limit the use of milk products
- Limit snack crackers, muffins, quick breads, croissants, and cakes made with extra fat, saturated or hydrogenated fat, whole eggs, or whole milk.
- Instead of using butter or margarine on bread, try dipping it in olive oil.
- Avoid fast foods (such as hamburgers, fries, fried chicken, and tacos), which are high in both total fat and saturated fat. When you eat out, choose broiled sandwiches or chicken without skin, salads with low-fat dressing, and foods that aren't fried. Ask the server to leave off the cheese and high-fat dressings like mayonnaise.
It is important to find out what your cholesterol numbers are because lowering cholesterol levels that are too high decreases the risk for developing heart disease and reduces the chance of a heart attack or dying of heart disease, even if you already have it.
In other words, lifestyle modifications can change pattern B to pattern A. When lifestyle changes alone are unsuccessful, medications can be used.
