Cholesterol and Heart Disease
This is a soft white waxy substance that is essential to health as it is a building block for all cell membranes, bile salts, vitamin D and various hormones. Cholesterol is only a problem if you have too much of it as this can increase your risk of heart disease.
Cholesterol comes from two sources. The majority is made in the body, mostly in the liver from saturated fat, but it is also found in foods that are obtained from animals, such as fatty meats, poultry, fish, seafood, eggs and dairy products.
A one per cent reduction in blood cholesterol can translate into a one to two per cent lower risk of heart disease.
What are ‘Good’ Cholesterol (HDL) and ‘Bad’ Cholesterol (LDL)?
Cholesterol is transported in the bloodstream in tiny ‘carriers’ called lipoproteins. The types of carrier are classified by their density, the two most important carriers being low-density lipoprotein (LDL) and high-density lipoprotein (HDL).
Most of the blood cholesterol is carried from the liver to the body’s tissues in low-density lipoproteins and is therefore called low-density lipoprotein cholesterol or LDL cholesterol. A high level of this increases your risk of heart disease. This is because, in modified forms, it can slowly build up in the walls of coronary arteries, forming ‘atherosclerotic plaques’, the fatty deposits that narrow the arteries and ultimately cause angina and heart attacks. To simplify matters, LDL cholesterol is often called ‘bad’ cholesterol, and the lower it is, the better.
Conversely, cholesterol carried in high-density lipoproteins is called HDL cholesterol. HDL cholesterol is thought of as ‘good’ cholesterol, as high levels reduce the risk of heart disease and low levels increase the risk of heart disease. HDL cholesterol seems to act as a ‘biological hoover’, removing cholesterol from the body cells, including artery walls, and returning it to the liver for excretion. The higher your HDL cholesterol, the lower will be your risk of heart disease.
What are Triglycerides?
Triglycerides are the most common form of fat both in the diet and in the human body and are often stored subcutaneously just where we don’t want them! Most of the triglycerides, a different kind of fat from cholesterol, are carried in very low density lipoprotein (VLDL).
These particles also contain small amounts of cholesterol which can be deposited in the wall of the artery, increasing the risk of heart disease. Very high levels of triglycerides can cause pancreatitis. High blood triglyceride levels are often seen in people who are overweight, have Type 2 diabetes or drink too much alcohol.
Research has shown that even if your cholesterol level is normal, if you have a high level of triglycerides and a low level of HDL cholesterol, you may still be at increased risk of heart disease. Keeping fit, slim and enjoying a healthy diet which includes oily fish or fish oil keeps triglyceride levels under control.
What are Lipids?
Lipids are the collective name for fatty substances in the blood. If you want to know your levels you will need to have a blood test. A fasting blood test (where you fast for 12-16 hours, drinking only water) will tell you the level of both LDL and HDL cholesterol as well as your level of triglycerides. A random, non-fasting test measures just the total and HDL cholesterol.
What is A Good Lipid Pattern?
The average cholesterol level of most people in the UK is around 5.4 mmol/L (211 mg/dL) yet in areas of rural China the average cholesterol level is 3.0mmol/L (115mg/dL) and the rate of heart disease in those places is very low. It is likely that the lower the cholesterol level, the better. If you can keep your cholesterol level low enough, there is a good chance that any atheroma, which has already been deposited, will stabilize or even regress.
If you already have heart disease or are at high risk of developing it, your doctor may have prescribed medication to modify your lipid levels. The benefits of these drugs are significant and their effect is enhanced by a healthy diet.
To keep your heart healthy, reasonable cholesterol levels to aim for are:
- Total cholesterol level below 5.0mmol/L (195mg/dL)
- LDL cholesterol level below 3.0mmol/L (115mg/dL)
- HDL cholesterol above 1.0mmol/L (39mg/dL)
- Triglyceride level below 1.7mmol/L (151 mg/dL)
If you have had a heart attack, stroke, diabetes or are at high risk of CVD, then lower targets are set for total cholesterol (below 4.0mmol/L (156mg/dL)) and LDL cholesterol (below 2.0mmol/L (78mg/dL).