Whenever we hear the word 'cholesterol' we think hamburgers, thickshakes, people who need a double seat in an aircraft, clogged arteries and an early death.
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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 essential for many of the body's metabolic processes. It helps make hormones like oestrogen, testosterone and adrenaline (the name originates from the Greek 'chole' meaning bile and stereos meaning solid). 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.
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 essential for many of the body's metabolic processes. It helps make hormones like oestrogen, testosterone and adrenaline (the name originates from the Greek 'chole' meaning bile and stereos meaning solid). 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.
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The trouble starts when we get too much cholesterol – when the intake of fats in our diet causes the levels of cholesterol in our blood to rise to more than we need.
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If it rises above normal levels – that is, 5.5 millimoles per litre – it can build up into fatty deposits on the surface of our arteries, which can form calcium plaques. These narrow the arteries and block blood from flowing, leading to heart disease, stroke and other conditions. This is a condition known as atherosclerosis. High cholesterol is one of the risk factors for atherosclerosis, along with smoking, being overweight, and having high blood pressure.
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Good fats, bad fats
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Most cholesterol is manufactured in the liver from fats in our diet. The liver makes cholesterol and attaches it to carrier molecules made of fat and protein called lipoproteins.
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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 arteries causing the damage.
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HDL, on the other hand, mops up cholesterol from the bloodstream and takes it back to the liver. So it reduces cholesterol, and lessens the chance of it being deposited in the arteries.
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HDL cholesterol is sometimes called 'good cholesterol' and LDL cholesterol 'bad cholesterol'. The more HDL you and 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 the types of fats we eat. Biochemists divide fats in our diets into different types, according to their chemical composition. They talk about saturated, monounsaturated and polyunsaturated fats. These terms refer to the differences in the numbers of hydrogen atoms in the fat molecules.
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How much LDL and HDL we have in our blood is influenced by the types of fats we eat. Biochemists divide fats in our diets into different types, according to their chemical composition. They talk about saturated, monounsaturated and polyunsaturated fats. These terms refer to the differences in the numbers of hydrogen atoms in the fat molecules.
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Eating a lot of saturated 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 full fat dairy products, processed meats like salami and sausages, snack foods like chips, takeaway foods (especially deep fried foods), cakes, biscuits and pastries, coconut oil and palm oil. If you want to avoid artery disease, stay away from these foods.
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Eating monounsaturated or polyunsaturated fats, on the other hand, tends to increase the levels of HDL. And HDL reduces cholesterol in the blood, so these fats are called 'good fats'. Eating these will reduce your risk of artery disease. Foods high in monounsaturated fats include olive oil, canola oil, avocados and most nuts. Foods high in polyunsaturated fats include oils of seeds and grains, such as sunflower, safflower, corn, soybeans and walnuts.
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Familial hypercholesterolaemia
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Familial hypercholesterolaemia
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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.
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Cholesterol test
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Cholesterol test
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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 few years. People younger than 45 who are at higher risk of coronary heart disease – for example, those who have a family history of hypercholesterolaemia, heart disease, high blood pressure and/or diabetes, should also have a regular cholesterol test.
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The National Heart Foundation recommends that all adults over 45 years old have a regular blood cholesterol test every few years. People younger than 45 who are at higher risk of coronary heart disease – for example, those who have a family history of hypercholesterolaemia, heart disease, high blood pressure and/or diabetes, should also have a regular cholesterol test.
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The test is a simple blood test taken after a period of fasting (not eating) for 12 hours. The test measures the total cholesterol level (LDL plus HDL and other fats called triglycerides). Normal is below 5.5 millimoles/litre. Most people are between 4 and 5.5. In someone young and healthy with no other risk factors, a little over 5.5 is acceptable. Individual LDL, HDL and triglyceride levels are sometimes also tested. Normal levels are:
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Total cholesterol: less than 5.5 mmol/l
LDL: less than 3.5 mmol/l
HDL: greater than 1.0 mmol/l
LDL to HDL ratio: less than 4
Triglycerides: less than 2.0 mmol/l.
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How to lower cholesterol
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LDL: less than 3.5 mmol/l
HDL: greater than 1.0 mmol/l
LDL to HDL ratio: less than 4
Triglycerides: less than 2.0 mmol/l.
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How to lower cholesterol
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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, he or she will recommend the following:
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Diet
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A diet low in saturated fats and high in monounsaturated and polyunsaturated fats. This means:
low-fat or reduced-fat milk, yoghurt and other dairy products
lean meat (meat trimmed of fat or labelled as 'heart smart')
limited fatty meats, including sausages and salami, with leaner sandwich meats like turkey breast or cooked lean chicken instead
fish (fresh or canned) at least twice a week
butter and dairy blends replaced with polyunsaturated margarines
plenty of fresh fruit, vegetables and wholegrain foods, nuts, legumes and seeds
plant sterols are a type of alcohol structurally similar to cholesterol and found in some margarines and fortified foods, in corn, rice, vegetable oils and nuts. They can also lower cholesterol.
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low-fat or reduced-fat milk, yoghurt and other dairy products
lean meat (meat trimmed of fat or labelled as 'heart smart')
limited fatty meats, including sausages and salami, with leaner sandwich meats like turkey breast or cooked lean chicken instead
fish (fresh or canned) at least twice a week
butter and dairy blends replaced with polyunsaturated margarines
plenty of fresh fruit, vegetables and wholegrain foods, nuts, legumes and seeds
plant sterols are a type of alcohol structurally similar to cholesterol and found in some margarines and fortified foods, in corn, rice, vegetable oils and nuts. They can also lower cholesterol.
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Exercise
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regular exercise (for example, at least 30 minutes of brisk walking daily). Exercise increases HDL levels and reduces LDL levels in the body.
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Medications
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After three months of diet and exercise, a doctor will usually do another cholesterol test. If it's still high (over 6.5, or if it's over 5.50 and the person has risk factors for artery disease), the next step may be to add medication to diet and exercise. People will familial hypercholesterolaemia will usually also need medications. There are several different types, which can be taken alone or in combination.
Statins. Also known as HMG CoA reductase inhibitors, these drugs block an enzyme (HMG CoA reductase) used in the production of cholesterol. They also accelerate turnover of cholesterol by the liver. Common statins are atorvastatin (brand name Lipitor), fluvastatin (Lescol or Vastin), pravastatin (Pravachol), and simvastatin (Lipex or Zocor). They can drop blood LDL levels by anywhere between 20 and 50 per cent, and increase HDL by 5 to 15 per cent. They're expensive, but they're on the Pharmaceutical Benefits Scheme. Side effects include stomach upset and headache.
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Statins. Also known as HMG CoA reductase inhibitors, these drugs block an enzyme (HMG CoA reductase) used in the production of cholesterol. They also accelerate turnover of cholesterol by the liver. Common statins are atorvastatin (brand name Lipitor), fluvastatin (Lescol or Vastin), pravastatin (Pravachol), and simvastatin (Lipex or Zocor). They can drop blood LDL levels by anywhere between 20 and 50 per cent, and increase HDL by 5 to 15 per cent. They're expensive, but they're on the Pharmaceutical Benefits Scheme. Side effects include stomach upset and headache.
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Cholestyramine and colestipol. These are older medications, also known as bile-acid-binding resins. They bind to bile acids in the intestine, preventing them from being absorbed into the body. The liver needs bile acids to make cholesterol – so less bile acids means less cholesterol. Examples include cholestyramine (brand name Questran Lite) and colestipol (Colestid granules). They both come in sachets of powder which need to be mixed with water, juice or other fluid and can be taken with or without food. Constipation is a common side effect.
Gemfibrozil and fenofibrate. These drugs are used when the others don't work, or when levels of triglycerides (another common type of fats) are high – though they also increase the amount of HDL in the blood. Fenofibrate also lowers total cholesterol.
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Gemfibrozil and fenofibrate. These drugs are used when the others don't work, or when levels of triglycerides (another common type of fats) are high – though they also increase the amount of HDL in the blood. Fenofibrate also lowers total cholesterol.
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Nicotinic acid can lower LDL (bad) cholesterol and triglycerides, and increase HDL cholesterol. It can cause flushing of the face and neck.
Ezetimibe (brand name Ezetrol) is a new drug in a class called the cholesterol absorption inhibitors. It works by reducing the absorption of cholesterol from the intestine into the bloodstream. It reduces total cholesterol and LDL, and increases HDL cholesterol.
Ezetimibe (brand name Ezetrol) is a new drug in a class called the cholesterol absorption inhibitors. It works by reducing the absorption of cholesterol from the intestine into the bloodstream. It reduces total cholesterol and LDL, and increases HDL cholesterol.
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