Not all cholesterol is bad for the body. There are two types of cholesterol - HDL (High Density Lipoprotein or good cholesterol) and LDL (Low Density Lipoprotein or bad cholesterol). While LDL causes blockage in arteries, HDL helps transport triglycerides to the liver for excretion.
What are HDL and LDL?
Good cholesterol (High Density Lipoprotein or HDL) is one of the groups of lipoproteins (fat-like substances) present in blood. HDL aids in the transport of cholesterol and triglycerides to the liver for excretion or re-utilization. Thus, good cholesterol prevents cardiovascular diseases by preventing the blockage of arteries.
Bad cholesterol (or LDL - Low Density Lipoprotein) is also a type of lipid present in the blood and if present in large amounts can cause health problems as it tends to accumulate in the arteries and cause blockage.
In fact, not all LDL causes atherosclerosis. There are two types of LDL: small dense LDL and large buoyant LDL. It is the small dense LDL that is more atherogenic. Small dense LDL enters the walls of blood vessels. When LDL gets oxidized, plaque builds up in the arterial walls, causing the obstruction of blood vessels.
Differences in Structure and Function
Lipoproteins are a complex of apolipoproteins and phospholipids. Good cholesterol is the smallest of all the lipid molecules, which are high-density molecules due to their high protein content. The function of good cholesterol is to transport cholesterol from the arteries and tissues to the liver and other organs such as ovary, adrenal glands, and testis. The cholesterol delivered to the liver is excreted into the bile, and then the intestines. The cholesterol transported to the other organs is used for the synthesis of steroid hormones. The other functions of HDL include their role in inhibiting oxidation, inflammation, activation of endothelium and coagulation.
An LDL molecule consists of a single Apo lipoprotein molecule which circulates the fatty acids. The main function of LDL is to transport cholesterol to tissues and arteries.
Effects of High Cholesterol
The higher the level of LDL cholesterol in your blood, the greater your chance is of getting coronary heart disease. The higher the level of HDL cholesterol in your blood, the lower your chance is of getting heart disease.
Coronary heart disease is a condition in which plaque builds up inside the coronary arteries. This limits the flow of oxygen-rich blood to your heart muscle.
Eventually, an area of plaque can rupture (break open). This causes a blood clot to form on the surface of the plaque. If the clot becomes large enough, it can mostly or completely block blood flow through a coronary artery.
If the flow of oxygen-rich blood to your heart muscle is reduced or blocked, angina or a heart attack may occur.
The recommended levels of HDL (good cholesterol) are 1.55mmol/L and above. In case of LDL (or bad cholesterol), 2.6mmol/L or lower is considered optimum for the body.
Food containing good and bad cholesterol
The foods rich in good cholesterol (HDL) include onions and Omega-3 fatty acids like flax oil, canola oil, fish, foods rich in fibre like grains, oats, bran and soy. To decrease your LDL, avoid high-cholesterol foods that are rich in trans fatty acids, refined carbohydrates such as white sugar and flour, cholesterol-rich foods such as egg yolk, liver, kidney; dairy products like cream cheese, and alcohol.
Impact of lifestyle
Changes in lifestyle and regular exercise and weight loss can also help to raise HDL levels and decrease the overall cholesterol level. Small changes like moving from vegetable oil to canola or olive oil in cooking also make a difference in the long run.