Skip to: Main Navigation | Main Content
or try the A-Z Library
Cholesterol is an essential substance in the body, but too much of the wrong kind of cholesterol increases your risk of heart disease. How do you keep your cholesterol levels healthy?
Whenever we hear the word 'cholesterol' we think hamburgers, butter, clogged arteries and early death.
In fact cholesterol is essential to life. It's a compound a steroid that occurs naturally in the body. It's manufactured by the liver and is also derived from the diet when we consume animal based foods.
Cholesterol is essential for many of the body's metabolic processes. It helps make hormones like oestrogen, testosterone and adrenaline. It's used in the production of vitamin D, and also in the production of bile acids, which help the body digest fat and absorb fat-soluble vitamins in the small intestine.
While the liver makes all of the cholesterol your body needs, we also consume 'dietary cholesterol' in food we eat. When the liver detects this dietary cholesterol it makes less, therefore maintaining a healthy balance in the bloodstream. The trouble starts however when we eat too much saturated fat as it decreases the removal of cholesterol from the bloodstream. This is why a diet high in saturated fat can be a major cause of elevated levels of cholesterol in the blood.
Higher than normal blood cholesterol levels can lead to a build-up of fatty deposits on the surface of our arteries, which can form calcium plaques. When this happens your arteries narrow and block the flow of blood, leading to heart disease, stroke and other conditions.
This is a condition known as atherosclerosis. High blood cholesterol is one of the risk factors for atherosclerosis, along with smoking, being overweight, having diabetes, depression, social isolation and having high blood pressure.
When the liver makes cholesterol, it attaches it to carrier molecules made of fat and protein called lipoproteins.
There are two major types of these 'carrier' lipoproteins low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL is the major carrier of cholesterol from the liver to the rest of the body. When cholesterol levels are excessive, LDL deposits cholesterol onto the inside of the artery walls causing the damage.
HDL, on the other hand, mops up cholesterol from the bloodstream and takes it back to the liver where it is broken down. This action lessens the chance of cholesterol being deposited in the arteries.
HDL cholesterol is sometimes called 'good cholesterol' and LDL cholesterol 'bad cholesterol'. The more HDL you have and the less LDL that is, the higher the ratio of HDL to LDL the lower your risk of artery disease.
How much LDL and HDL we have in our blood is influenced by genetics, bodyweight and the types of fats we eat. There are three major types of fats found in foods and these are named according to their chemical composition. They include saturated, monounsaturated and polyunsaturated fats. These terms refer to the differences in the numbers of hydrogen atoms in the fat molecules. Another type of fat which is present in our diet in much smaller amounts compared to the other types, is trans fat. Trans fat is a type of unsaturated fat that acts in the body like saturated fat.
Eating a lot of saturated or trans fat tends to elevate the levels of LDL in the blood, so these kinds of fats are often called 'bad fats'. Foods high in saturated fats include, butter, processed meats like salami and sausages, fat on the outside of meat, takeaway foods (especially deep fried foods), cakes, biscuits and pastries, coconut oil and palm oil. Foods high in trans fats include commercial donuts (depending on the brand) and foods that list 'hydrogenated fats/oils' in the ingredient list. If you want to reduce your risk of artery disease, it's best to minimise these foods in your diet.
Eating foods that contain polyunsaturated fats, on the other hand, tends to increase the levels of HDL and reduce the level of LDL in the bloodstream. Eating foods rich in monounsaturated fats in place of saturated or trans fats in the diet, also reduces levels of LDL so foods rich in these fats are good to eat. Polyunsaturated and monounsaturated fats are generally referred to as 'good fats'. Eating these will reduce your risk of artery disease. Foods high in monounsaturated fats include olive oil, canola oil, avocados, peanuts, hazelnuts, almonds and macadamia nuts. Foods high in polyunsaturated fats include oils of seeds and grains, such as sunflower, safflower, corn, soybeans, Brazil nuts, pine nuts and walnuts as well as fish.
While some fad diets and popular nutrition books have recently warned against the use of nut and seed oils, this recommendation is not backed up by scientific evidence. The Heart Foundation, in its review of the evidence around fats and oils and heart disease, recommends the reduction of saturated and trans fats and the replacement of these fats with polyunsaturated and monounsaturated fats. In practice, this means incorporating use of nut and seed oils in place of fats, such as butter and coconut oil.
In some people, cholesterol levels are high because they have a familial (inherited) condition in which cholesterol isn't properly cleared by the liver and builds up in the blood. These people have a high risk of arterial disease, heart attack and stroke and at an early age. It's a dominant genetic disorder; a person inherits it from one parent, and has a one in two chance of passing it on. It affects about one person in 500.
How do you know if you have abnormally high cholesterol? You don't it doesn't produce any symptoms and many people first learn they have high cholesterol only when they have a heart attack or a stroke.
The National Heart Foundation recommends that all adults over 45 years old have a regular blood cholesterol test every year. But you should start testing earlier than 45 if you have a strong family history of high cholesterol, heart disease, high blood pressure and/or diabetes or if you're Aboriginal or a Torres Strait Islander.
The test is a simple blood test taken after a period of fasting (not eating) for 12 hours.
But on-the-spot tests that don't involve you fasting known as "random" cholesterol tests are sometimes offered through mobile services set up by community groups. Although less reliable than tests done after fasting, random tests can still be a good idea because if your result is in the normal range from a random test it's extremely unlikely you're going to have high cholesterol.
If on the other hand, a random test suggests your cholesterol is not normal, you do then need to talk this through with your doctor, who may follow up with a more reliable fasting test.
Your cholesterol test result is not a single number but rather a suite of numbers. In general, you should aim for a total cholesterol of less than 4, an HDL ("good" cholesterol) level of more than 1, an LDL ("bad" cholesterol) level less than 2 and a level of fats called triglycerides less than 2. But total cholesterol and HDL are the most important numbers for otherwise healthy people.
It's worth taking steps to lower cholesterol because lowering cholesterol by 10 per cent reduces the risk of heart attack by 20 per cent. So if your doctor finds you have elevated cholesterol, they will recommend lifestyle measures and sometimes medication.
Lifestyle measures can start reducing cholesterol in as little as six weeks but for maximum impact, people are usually advised to try changing their habits for three to six months. (However, since changing lifelong habits can be hard and relapses are common, you may need even longer periods of time.)
Changing your diet has the greatest lifestyle influence on your cholesterol (10 to 15 per cent depending on how big a dietary change you can make). A diet low in saturated and trans fats and which contains moderate amounts of monounsaturated and polyunsaturated fats is recommended. Including fibre rich foods can also help reduce LDL cholesterol levels. This means:
After a period of diet and exercise changes, your doctor will do another cholesterol test. If it's still high, the next step may be to add medication to diet and exercise.
People with familial hypercholesterolaemia will usually also need medications. There are several different types, which can be taken alone or in combination.
First published: 03/08/2006