Since the type and amount of Cholesterol in our body can have important health effects on our cardiovascular system, it's a good idea to understand what Cholesterol is, how it affects our health and how to manage our blood Cholesterol levels. Such understanding helps us take better care of our heart and live a healthier life, reducing our personal risk for heart attack and stroke in the process.
What is Cholesterol?
Cholesterol is a waxy substance that belongs to the fat family or to a class of molecules called steroids. Cholesterol plays an important role in the body. It is an essential building material of the body's every cell and necessary for manufacturing a number of important hormones, bile and vitamin D that are essential for normal body functions. Cholesterol is naturally present in cell walls or membranes everywhere in the body, including the brain, nerves, muscles, skin, liver, intestines and heart.
What are the functions of Cholesterol?
- It builds and maintains cell membranes (outer layer), it prevents crystallization of hydrocarbons in the membrane
- It is essential for determining which molecules can pass into the cell and which cannot (cell membrane permeability)
- It is involved in the production of sex hormones (the body's chemical messengers e.g. Estrogens and Androgens)
- It is essential for the production of hormones released by the adrenal glands (cortisol, corticosterone, aldosterone and others)
- It aids in the production of bile. It converts sunshine to vitamin D and it insulates nerve fibers
- It is important for the metabolism of fat soluble vitamins, including vitamins A, D, E and K
Where does our body get Cholesterol from?
We get Cholesterol in two ways. The first source is the body itself, mainly the liver, which produces varying amounts, usually about 1000 milligrams a day. The second source is the food that we eat which is derived from animals (especially egg yolks, meat, poultry, whole-milk and dairy products). Foods from plants (fruits, vegetables, grains, nuts and seeds) do not contain Cholesterol. After a meal, Cholesterol is absorbed by the intestines into the blood circulation and is then packaged inside a protein coat. This Cholesterol-protein coat complex is called a chylomicron.
The liver is capable of removing Cholesterol from the blood circulation as well as manufacturing Cholesterol and secreting Cholesterol into the blood circulation. After a meal, the liver removes chylomicrons from the blood circulation. In between meals, the liver manufactures and secretes Cholesterol back into the blood circulation. Too much Cholesterol can have negative impacts on our health.
What are the different types of Fats in our Body?
Fats travel in the blood in two forms; Cholesterol and triglycerides.
Blood is watery and Cholesterol is fatty. Just like oil and water, the two do not mix. To travel in the bloodstream, Cholesterol is carried in small packages called lipoproteins. The small packages are made of fat (lipid) on the inside and proteins on the outside. There are two main types of lipoproteins: low-density lipoprotein (LDL) and high-density lipoprotein (HDL).
Low-density lipoprotein (LDL) is also known as 'bad' Cholesterol. LDL carries Cholesterol from the liver to cells. If too much LDL circulates in the blood, it can slowly build up on the walls of the arteries feeding the heart and brain and result in the formation of fatty streaks. These fatty streaks slowly increase in size and produce raised areas called fibrous plaques. Over the years these plaques increase in size and ultimately can block the blood flow to part of the heart and cause a heart attack. If the blood flow to the brain is blocked, a stroke can result.
High-density lipoprotein (HDL) is also known as 'good' Cholesterol as it helps so carry Cholesterol away from the arteries to the liver, where it is processed and excreted from the body. It removes excess Cholesterol from the blood thus providing protection against a heart attack or stroke. Thus, high levels of LDL Cholesterol and low levels of HDL Cholesterol (high LDL/HDL ratios) are risk factors for atherosclerosis, while low levels of LDL Cholesterol and high level of HDL Cholesterol (low LDL/HDL ratios) are desirable.
Triglycerides - these are the chemical forms in which most fat exists in the body, as well as in food. They are present in blood plasma. Triglycerides, in association with Cholesterol, form the plasma lipids (blood fat). Triglycerides in plasma originate either from fats in our food or are made in the body from other energy sources, such as carbohydrates. Calories we consume but are not used immediately by our tissues are converted into triglycerides and stored in fat cells. When our body needs energy and there is no food as an energy source, triglycerides will be released from fat cells and used as energy - hormones control this process.
How does high blood Cholesterol cause Heart Disease?
Our body makes all the Cholesterol that it needs. However, over a period of years, extra Cholesterol from the animal products that we eat builds up on the walls of the arteries in the form of plaques. These plaques gradually increase in size and make the arteries supplying blood to the heart narrower and narrower. As a result, less blood gets to the heart. Blood carries oxygen to the heart and if enough oxygen-rich blood cannot reach to heart, you may suffer chest pain called 'Angina'. If the blood supply to a portion of the heart is completely cut off the result is a heart attack.
Sometimes, plaques dislodge or produce a clot and obstruct the arteries resulting in 'Angina' or a heart attack. A raised level of Cholesterol has also been linked to other diseases including dementia and kidney failure.
Besides Cholesterol, a high level of triglycerides in the blood may also increase the risk of heart disease.
What makes our Blood Cholesterol High?
There ore several factors that can raise our blood Cholesterol level:
- Diet rich in saturated fats
- Physical inactivity
- Certain diseases e.g. diabetes, diseases of the kidney and the thyroid gland
- Use of oral contraceptives
- Increased age
- Gender - women during childbearing age usually have a lower Cholesterol level than those of men of the same age.
- Hereditary factors
What are the symptoms of High Blood Cholesterol?
Generally high blood Cholesterol itself does not cause any symptoms and that is why it is known as the "silent killer".
How is Blood Cholesterol measured?
It is recommended that every adult should be screened for blood Cholesterol. The Cholesterol level in the blood is measured in a sample token in the morning after a 12-hour fast.
It is best to have a blood test called a 'lipoprotein profile'.
This test gives information about our: Total blood Cholesterol, LDL (bad) Cholesterol, HDL (good) Cholesterol and Triglycerides.
What are the healthy levels of Cholesterol and Triglycerides?
Total Cholesterol is the sum of LDL (low density) Cholesterol, HDL (high density) Cholesterol, VLDL (very low density) Cholesterol and IDL (intermediate density) Cholesterol.
It is important to know that there are two main methods of describing concentrations of Cholesterol: by weight i.e. milligrams (mg) of cholesterol per deciliter (dL) of blood and by molecular count i.e. millimoles (mmol) of cholesterol per liter (L) of blood. To understand and describe the test results you should remember the units used for the measurement of your Cholesterol level. See how your cholesterol numbers compare to the tables below.