What is cholesterol?
Cholesterol is a soft, wax-like substance that is found in every cell in our body. It performs several important functions in the body: it makes up part of the walls of each cell; it is a key component in the manufacture of hormones; it helps produce bile acids, which help promote the absorption of fat from our diets.
The body is capable of producing all of the cholesterol needed for these purposes so extra cholesterol from the diet is not required.
Is some cholesterol good for me?
Several forms of cholesterol and triglyceride, collectively called lipids, are found in the blood stream.
LDL (low density lipoprotein) cholesterol accounts for most of the cholesterol in the blood stream. LDL is the form of cholesterol that enters the lining of artery walls.
When LDL levels are high, especially in someone who smokes, or has high blood pressure or diabetes, the build up of LDL in the arteries grows more quickly and forms plaques. These plaques can clog up the arteries, reducing blood flow to vital tissues (e.g. heart muscle, brain).
This condition is known as atherosclerosis (which means "hard porridge" because of how these plaques look inside the arteries). If one of these plaques tears, a clot (or thrombus) may form, blocking the flow of blood to part of the heart muscle. The result is a heart attack. If a clot blocks the flow of blood to part of the brain, the result is a stroke.
A quick way to remember that LDL is the bad cholesterol is L for LDL, L for "Lousy cholesterol".
HDL (high density lipoprotein) cholesterol carries cholesterol in a form that does not damage the artery walls. HDL is known as "good" cholesterol because a high level of HDL seems to protect against heart attack by removing excess cholesterol from atherosclerotic plaques.
HDL accounts for 20-25% of the total cholesterol level. The higher the HDL level, the better. A quick way to remember that HDL is the good cholesterol is H for "healthy cholesterol".
Lp(a) is a cholesterol carrying particle that looks very like LDL but also carries a small protein called apo(a). The level of Lp(a) in our bodies is genetically determined. High levels are associated with an increased risk of heart disease particularly when LDL cholesterol levels are also high. Because Lp(a) also has effects in promoting clot formation, it is considered an important risk factor for heart disease.
What is the recommended cholesterol level?
Many studies have shown that a high level of total cholesterol in the blood is associated with increased risk of coronary heart disease. A total cholesterol level of less than 5.0 mmol/L is advised, particularly in people at high risk for heart disease (i.e. those with a family history of heart disease; those with diabetes; those with high blood pressure).
What makes my cholesterol levels rise?
Your blood cholesterol level is affected not only by what you eat but also by how quickly your body makes LDL ("bad") cholesterol and disposes of it. Many factors help determine whether your LDL-cholesterol level is high or low, including:
- Your genes. Our genes influence how high our LDL ("bad") cholesterol is by affecting how fast LDL is made and removed from the blood. One specific form of inherited high cholesterol is familial hypercholesterolemia, which often leads to heart disease at a very early age.
- Your diet. Your body is capable of making all the cholesterol it needs; it is not necessary to take in any additional cholesterol from the foods you eat. A high intake of animal fats, i.e. saturated fats, and a low intake of polyunsaturated fats increases the risk of coronary heart disease by increasing LDL cholesterol. Eating fruit and vegetables helps to reduce the risk of LDL forming plaques in the lining of artery walls. High fibre intake may increase HDL cholesterol levels.
- Weight. Overweight individuals often have high LDL cholesterol levels because their diet is usually rich in fat.
- Physical activity/exercise. Regular physical activity may lower LDL ("bad") cholesterol and raise HDL ("good") cholesterol levels. At least 30 minutes of exercise every day is recommended.
- Age and gender. Heart disease has traditionally been considered a man's disease because women usually have total cholesterol levels that are lower than those of men the same age. However, heart disease is a leading cause of health problems in women, especially after the menopause, which often causes an increase in their LDL ("bad") cholesterol and a decrease in their HDL ("good") cholesterol level. After the age of 50, women often have higher total cholesterol levels than men of the same age.
- Alcohol. Moderate alcohol intake (an average of one to two glasses of red wine per day for men and one glass per day for women) increases HDL ("good") cholesterol. However, it does not lower LDL ("bad") cholesterol. Doctors don't know for certain whether moderate alcohol intake also reduces the risk of heart disease. Drinking too much alcohol can damage the liver and heart muscle, leading to high blood pressure and raised triglycerides. Because of the risks, alcoholic beverages should not be used as a way to prevent heart disease.
- Stress. Several studies have shown that in the long-term, stress can raise blood cholesterol levels. One way that stress may do this is by affecting your habits. For example, many people use alcohol and cigarettes as a way of coping with stress. They may also console themselves by overindulging eating fatty foods.
- Smoking. Smoking can lower the level of the healthy HDL cholesterol. Smoking also increases the potential to oxidise lipoprotein particles producing a damaged form of lipoproteins which really increases one's risk of heart disease.
Written by Medpages Editorial Team
Last Editorial Review:20/1/2010
