Cholesterol is a waxy substance that is produced by the liver and is essential for many bodily functions, including the formation of some hormones and the creation of membranes to protect our cells. Most cholesterol (about 80%) is made within our body and the rest we get from food. Cholesterol travels in our blood stream to where it’s needed in a substance called lipoproteins. Lipoproteins are a combination of fats and cholesterol.
When cholesterol is coated with lipoproteins it dissolves easily and flows freely. When it’s not coated with lipoproteins, it’s less soluble, so fatty deposits start to build up inside our arteries. High cholesterol is a risk factor for cardiovascular disease and stroke.
How cholesterol is tested and what the results mean
Cholesterol levels are tested with a simple blood test. You may be asked not to eat for 12 hours prior so that any food you’ve eaten will not affect the results.
The test will check three things: the amount of low-density lipoproteins (LDL) in your blood - often known as ‘bad cholesterol’, the levels of high-density lipoproteins (HDL) in your blood - dubbed ‘good cholesterol’, and triglycerides (other fatty substances).
LDL is bad because it deposits cholesterol in the lining of your arteries. As fatty deposits build up over time the arteries narrow and harden (a condition called coronary atherosclerosis) increasing your risk of cardiovascular disease.
HDL is good because it mops up excess cholesterol in your body and returns it to the liver for re-processing. Raised levels of HDL are protective against heart disease.
Blood cholesterol is measured in units called millimoles per litre of blood - shortened to mmol/L. Healthy levels of total cholesterol should be 5mmol/L or less with LDL being 3mmol/L or under, while it’s best to have a level of 1.6 mmo/L or higher of HDL (good cholesterol).
You may have your triglyceride levels measured at the same time - this is another measure of fat in the body. A reading below 1.7mmol/L is desirable.
How high cholesterol is treated
Patients with high cholesterol should make dietary changes reducing their intake of salt and animal fats, while increasing foods such as oily fish, fruit and vegetables. But, because most cholesterol is produced in the liver, a low cholesterol diet is often not sufficient. Many patients will also require prescribed cholesterol-lowering drugs called statins, which are highly effective.