Cholesterol is a soft, waxy, fatty substance found in the bloodstream and in body cells. It is used to form cell membranes and hormones in the body of animals. Cholesterol can’t dissolve in the blood. It is transported by carriers called lipoproteins, which can be LDL ( low-density lipoprotein ), VLDL ( very low-density lipoprotein ) and HDL ( High-density lipoprotein ).
Low-density lipoprotein is the major cholesterol carrier in the blood. It transports fat to the muscles, heart, fat stores and other tissues. If too much LDL cholesterol circulates in the blood, it can slowly build up in the walls of arteries feeding the heart and brain. Together with other substances it can form plaque, a thick, hard deposit that can clog arteries (atherosclerosis).
HDL tends to carry cholesterol away from the arteries and back to the liver for recycling and/or excretion through bile. HDL cholesterol is known as “good” cholesterol because HDL removes cholesterol from arteries and blood and transports it to the liver for breakdown and disposal or use in such purposes as the starting point for the manufacture of hormones. A high HDL cholesterol level seems to protect against heart attacks, while a low HDL cholesterol level is linked to higher risks of strokes and heart attacks.
Cholesterol in the human blood originates from two major sources. The liver typically produces all the cholesterol the body needs and it is not necessary to take in any additional cholesterol from food. Secondly, cholesterol is obtained from dietary items like egg yolks, fatty meats, fish, seafood, whole milk, ice cream and dairy products. Saturated fatty acids and trans fats are the main culprits in raising blood cholesterol. The American Heart Association recommends that average daily cholesterol intake be limited to less than 300mg. If heart disease has been diagnosed, limit the daily intake to less than 200mg.
Genes influence LDL cholesterol levels by affecting how speed of fabrication and removal from the blood. Inherited hypercholesterolemia affects 1 in 500 people, which is why some people with a cholesterol free diet show high blood cholesterol levels.
Regular physical activity may lower LDL cholesterol and raise HDL cholesterol levels. Physical activity can also help to reduce excess weight, diabetes and high blood pressure. Inactivity is a major risk factor for heart disease. Even moderate-intensity activities, if done daily, help reduce the risk. Examples include walking for pleasure, gardening, yard work, housework, dancing and prescribed home exercise. People who reduce their body weight also reduce their blood cholesterol levels.
Smoking increases LDL cholesterol levels while HDL-cholesterol goes down, resulting in an unfavorable HDL/LDL ratio. It also increases the tendency for blood to clot and may provoke a heart attack. In addition, tobacco smoke contains chemical components which cause serious damage to blood vessels.
Alcohol intake increases HDL cholesterol but does not lower LDL cholesterol. If you drink, do so in moderation. People who consume moderate amounts of alcohol (an average of one to two drinks per day for men and one drink per day for women) have a lower risk of heart disease than non-drinkers. However, increased consumption of alcohol leads to other health dangers such as alcoholism, high blood pressure, obesity, stroke, cancer, suicide and damage to liver cells and the heart muscle. Because of these risks, alcoholic beverages should not be used as a way to prevent heart disease. The benefit isn’t great enough to recommend drinking alcohol if you don’t do so.
Before menopause, women usually have total cholesterol levels lower than those of men at the same age. As both get older, their blood cholesterol levels rise until about 60 or 65 years of age. After the age of 50, women often have higher total cholesterol levels than men of the same age.
Estrogen increases HDL cholesterol levels, which explains why pre-menopausal women generally have higher HDL levels than men.
Over the long term, stress has been shown to raise blood cholesterol levels. One way this may occur is through altered eating habits. Under stress, some people console themselves by eating more, especially ice-cream or other high cholesterol foods. The saturated fat and cholesterol in these foods contribute to higher levels of blood cholesterol. Stress also increases the risk of blood clots.
LDL lipoprotein deposits cholesterol on artery walls, causing the formation of a hard, thick substance called cholesterol plaque. Over time, this plaque causes thickening of the artery walls and narrowing of the arteries, a process called atherosclerosis. When coronary arteries are narrowed, they are incapable of supplying enough blood and oxygen to the heart muscle. This causes chest pain, and formation of a blood clots can completely block arteries, leading to death of heart muscle (heart attack).
The Framingham Heart Study established that high blood cholesterol is a risk factor for coronary heart disease (CHD). The higher the cholesterol level, the greater the CHD risk. Recent studies have shown that lowered cholesterol l reduced the number of heart attacks and deaths in people with high blood cholesterol levels. The need for bypass surgery or angioplasty was also reduced significantly. The National Cholesterol Education program recommends that everyone over the age of 20 be tested for cholesterol at least once every 5 years if LDL cholesterol is less than 130 mg/dl and every 1-3 years if LDL cholesterol is borderline (between 130 to 160 mg/dl).
|BLOOD LIPID PARAMETERS|
|Total Cholesterol||< 200 mg/dl||200 - 239 mg/dl||≥ 240 mg/dl|
|LDL Low-Density Lipoproteins||< 130 mg/dl||130 - 159 mg/dl||≥ 160 mg/dl|
|HDL High-Density Lipoproteins||> 35 mg/dl (values >60mg/dl are considered a negative risk factor)|
|Triglycerides||< 200 mg/dl|