What is cholesterol?
Cholesterol is a fatty substance known as a lipid and is vital for the normal functioning of the body. It's mainly made by the liver but can also be found in some foods we eat.
Having an excessively high level of lipids in your blood (hyperlipidemia) can have an effect on your health. High cholesterol itself doesn't cause any symptoms, but it increases your risk of serious health conditions.
Cholesterol is carried in your blood by proteins, and when they combine they're called lipoproteins. There are harmful and protective lipoproteins known as low-density lipoprotein (LDL) and high-density lipoprotein (HDL), or bad and good cholesterol.
- LDL carries cholesterol from your liver to the cells that need it. If there's too much cholesterol for the cells to use, it can build up in the artery walls, leading to disease of the arteries. For this reason, LDL cholesterol is known as "bad cholesterol"
- HDL carries cholesterol away from the cells and back to the liver where it's either broken down or passed out of the body as a waste product. For this reason, it's referred to as "good cholesterol" and higher levels are better
The amount of cholesterol in the blood (both LDL and HDL) can be measured with a blood test. The recommended cholesterol levels in the blood vary between healthy adults and those at higher risk.
Why should I lower my cholesterol?
Evidence strongly indicates that high cholesterol can increase the risk of:
This is because cholesterol can build up in the artery wall, restricting the flow of blood to your heart, brain and the rest of your body. It also increases the chance of a blood clot developing somewhere.
What causes high cholesterol?
There are many factors that can increase your chance of having heart problems or stroke if you have high cholesterol, including the following:
- an unhealthy diet – some foods already contain cholesterol (known as dietary cholesterol) but it's the amount of saturated fat in your diet which is more important
- smoking – a chemical found in cigarettes called acrolein stops HDL from transporting LDL to the liver, leading to narrowing of the arteries (atherosclerosis)
- having diabetes or high blood pressure (hypertension)
- having a family history of stroke or heart disease
There's also an inherited condition known as familial hypercholesterolaemia (FH). This can cause high cholesterol even in someone who eats healthily.
When should I test my cholesterol levels?
Your doctor may recommend you have your blood cholesterol levels tested if you:
- have been diagnosed with coronary heart disease, stroke or mini-stroke (TIA) or peripheral arterial disease (PAD)
- are over 40
- have a family history of early cardiovascular disease
- have a close family member who has a cholesterol-related condition
- are overweight
- have high blood pressure, diabetes or a health condition that can increase cholesterol levels, such as an underactive thyroid
How can I lower my cholesterol levels?
The first step in reducing cholesterol is to maintain a healthy, balanced diet. It's important to keep your diet low in fatty food, especially food containing saturated fat, and eat lots of fruit, vegetables and wholegrain cereals. This will also help to prevent high cholesterol from returning.
Other lifestyle changes can also make a big difference. It will help to lower your cholesterol if you do regular exercise and quit smoking.
If these measures aren't helping to reduce your cholesterol and you continue to be at a high risk of heart disease, your doctor may prescribe a cholesterol-lowering medication such as statins. Your doctor will take into account the risk of any side effects from statins and the benefit of lowering your cholesterol must outweigh any risks.
Causes of high blood cholesterol
Lots of different factors can contribute to high blood cholesterol, including diet, age, family history and ethnic group.
Your lifestyle can increase your risk of developing high blood cholesterol. This includes:
- an unhealthy diet. Some foods, such as liver, kidneys and eggs, contain cholesterol (known as dietary cholesterol). However, this has little effect on blood cholesterol and it's the amount of saturated fat in your diet which is more important. Read more information about preventing high cholesterol
- lack of exercise or physical activity. This can increase your level of "bad cholesterol" (low-density lipoprotein)(LDL)
- obesity. If you're overweight, you're likely to have higher levels of LDL cholesterol and triglycerides, and a lower level of high-density lipoprotein (HDL).
- drinking excessive amounts of alcohol. Regularly drinking a lot of alcohol can increase your cholesterol and triglyceride levels
- smoking. A chemical found in cigarettes called acrolein stops "good cholesterol" (HDL) from transporting the "bad cholesterol" (LDL) to the liver, leading to narrowing of the arteries (atherosclerosis)
Treating the underlying condition can help to reduce cholesterol.
There are a number of factors associated with high cholesterol that cannot be changed. Doctors refer to these as fixed factors and they include:
- family history of early heart disease or stroke. You're more likely to have high cholesterol if you have a close male relative (father or brother) aged under 55 or a female relative (mother or sister) aged under 65 who has had coronary heart disease or stroke
- a family history of a cholesterol-related condition, for example, if a close relative, such as a parent, brother or sister, has familial hypercholesterolaemia (see below)
- age. The older you are, the greater the likelihood of your arteries narrowing (atherosclerosis)
- ethnic group. People who are of Indian, Pakistani, Bangladeshi or Sri Lankan descent have an increased risk of high blood cholesterol
If you have a fixed risk factor (or a number of fixed risk factors) it's even more important to look at your lifestyle and any underlying conditions that you may have.
Familial hypercholesterolaemia is the medical term for high cholesterol that runs in the family. It's not caused by an unhealthy lifestyle, but by genetics. About 1 in 500 people inherit the condition from a parent.
Cholesterol is not cleared properly from your bloodstream and living with higher levels of cholesterol produces early heart problems.
Diagnosing high blood cholesterol
Blood cholesterol levels are measured with a simple blood test. This blood sample will be used to determine the amount of LDL (bad cholesterol), HDL (good cholesterol) and triglycerides (other fatty substances) in your blood.
You may be asked not to eat for 10-12 hours before the test (usually including when you are asleep at night). This ensures that all food is completely digested and won't affect the outcome of the test.
Your doctor or practice nurse can carry out the blood test and will take a blood sample either using a needle and a syringe or by pricking your finger.
Normal cholesterol level
Blood cholesterol is measured in units called millimoles per litre of blood, often shortened to mmol/L.
The government recommends that total cholesterol levels for healthy adults should be 5mmol/L or less, with levels of low-density lipoprotein (LDL) being 3mmol/L or less.
Adults at high risk are defined as those with existing heart disease, high blood pressure (hypertension), diabetes or those with a family history of early heart disease. Those at high risk should have a total cholesterol level of 4mmol/L or less, with levels of LDL being 2mmol/L or less.
Who should be tested?
Your doctor may recommend that you have your blood cholesterol levels tested if you:
- have been diagnosed with coronary heart disease, stroke or mini-stroke (TIA) or peripheral arterial disease (PAD)
- are over 40
- have a family history of early cardiovascular disease (for example, if your father or brother developed heart disease or had a heart attack or stroke before the age of 55, or if your mother or sister had these conditions before the age of 65)
- have a close family member who has a cholesterol-related condition, such as familial hypercholesterolaemia (inherited high cholesterol)
- are overweight or obese
- have high blood pressure or diabetes
- have another medical condition such as a kidney condition, an underactive thyroid gland or an inflamed pancreas (pancreatitis). These conditions can cause increased levels of cholesterol or triglycerides
Assessing your risk
When assessing your risk of heart attack or stroke, your doctor or nurse may refer to your cholesterol ratio. This is your total cholesterol level divided by your level of HDL cholesterol.
Cholesterol levels or cholesterol ratio should not be looked at on their own. Other factors should be taken into consideration when assessing your risk, including:
- your BMI (body mass index), which measures your weight in relation to your height
- treatable risk factors, such as high blood pressure (hypertension), diabetes and other medical conditions
- your age, sex, family history and ethnicity
At the end of your assessment, you'll be told whether you have a high, moderate or low risk of getting cardiovascular disease (heart disease or stroke) within the next 10 years.
Your doctor or nurse may also measure your level of triglycerides. Triglycerides are the fats you use for energy and come from the fatty foods you eat. You store what you don't use in the fatty tissues of your body. Excess triglycerides in the blood also increase heart problems.
Treating high cholesterol
If you've been diagnosed with high cholesterol, you'll at first be advised to make changes to your diet and increase your level of exercise.
After a few months, if your cholesterol level hasn't dropped, you'll usually be advised to take cholesterol-lowering medication.
Changing your diet, stopping smoking and doing more exercise will also help prevent high cholesterol from developing.
Eating a healthy diet that's low in saturated fats can reduce your level of LDL (bad cholesterol).
Try to avoid or cut down on the following foods, which are rich in saturated fat:
- fatty cuts of meat and meat products, such as sausages and pies
- butter, ghee and lard
- cream, soured cream, creme fraiche and ice cream
- cheese, particularly hard cheese
- cakes and biscuits
- coconut oil, coconut cream and palm oil
According to the Food Standards Agency:
- the average man should have no more than 30g of saturated fat a day
- the average woman should have no more than 20g of saturated fat a day
To get an idea of how much saturated food you are consuming, take a look at the food labels of the foods you are eating.
Omega-3 fatty acids
Many experts believe that the fats found in oily fish such as mackerel, salmon and tuna are good for you. These are known as omega-3 fatty acids and high doses can improve (lower) triglyceride levels in some patients.
There are several different types of cholesterol-lowering medication that work in different ways. Your doctor can advise you about the most suitable type of treatment. Your doctor may also prescribe medication to lower high blood pressure (hypertension) if it affects you.
The most commonly prescribed medications are outlined below.
Statins block the enzyme (a type of chemical) in your liver that helps make cholesterol. This leads to a reduction in your blood cholesterol level.
You'll usually be started on the drug simvastatin (Zocor). Other statins include atorvastatin (Lipitor) and rosuvastatin (Crestor).
When someone has side effects from using a statin, this is described as "intolerance" to it. Side effects of statins include muscle pain and stomach problems.
Statins will only be prescribed to people who continue to be at high risk of heart disease as you usually need to take statins for life. This is because cholesterol levels start to rise again once you stop taking them.
In some cases, a low daily dose of aspirin may be prescribed, depending on your age (children under 16 should not take aspirin) and other factors. Low-dose aspirin can prevent blood clots from forming.
Niacin is a B vitamin that's found in foods and multivitamin supplements. In high doses (available by prescription), niacin lowers LDL and triglycerides and raises HDL. However, it can cause side effects, particularly flushing (turning red in the face), so isn't commonly used. Taking high doses for a long time could also lead to liver damage.
The Department of Health advises that you should be able to get the amount of niacin you need by eating a varied and balanced diet. If you take niacin supplements, don't take too much because this might be harmful.
Ezetimibe is a medication that blocks the absorption of cholesterol from food and bile juices in your intestines into your blood. It's generally not as effective as statins, but is less likely to come with side effects.
You can take ezetimibe at the same time as your usual statin if your cholesterol levels are not low enough with the statin alone. The side effects of this combination are generally the same as those of the statin alone (muscle pain and stomach problems).
You can take ezetimibe by itself if you're unable to take a statin. This may be because you have another medical condition or you take medication that interferes with how the statin works, or because you experience side effects from statins. Ezetimibe taken on its own rarely causes side effects.
Preventing high cholesterol
You can help to lower your cholesterol by eating a healthy, balanced diet that's low in saturated fat, doing regular exercise, stopping smoking and cutting down on alcohol.
Eating an unhealthy diet that's high in fat will cause fatty plaques to build up in your arteries. This is because fatty foods contain cholesterol.
There are also 2 types of fat, saturated and unsaturated. Avoid foods that contain saturated fats because they will increase the levels of bad cholesterol in your blood. Foods high in saturated fat include:
- meat pies
- sausages and fatty cuts of meat
- ghee (a type of butter often used in Indian cooking)
- hard cheese
- cakes and biscuits
- food that contains coconut or palm oil
Eating a small amount of unsaturated fat will increase the level of good cholesterol and help reduce any blockage in your arteries. Foods that are high in unsaturated fat include:
- oily fish (mackerel, salmon, tuna)
- nuts and seeds
- sunflower, rapeseed and olive oil
Eating a low-fat diet that includes lots of fibre, such as wholegrain rice, bread and pasta, and plenty of fruit and vegetables, has also been proven to help lower cholesterol. Fruit and vegetables are full of vitamins, minerals and fibre and help keep your body in good condition. Aim to eat 5 80g portions of fruit and vegetables every day.
A chemical found in cigarettes called acrolein stops "good cholesterol" (HDL) from transporting the "bad cholesterol" (LDL) to the liver, leading to high cholesterol and narrowing of the arteries (atherosclerosis). This means that smoking is a major risk factor for both heart attacks and strokes.
If you're committed to giving up smoking but don't want to be referred to a stop smoking service, your doctor should be able to prescribe medical treatment to help with any withdrawal symptoms that you may experience after giving up.
Being active and taking regular exercise will help to increase the levels of "good cholesterol" (HDL) in your body by stimulating the body to move the "bad cholesterol" (LDL) to the liver so that it can be broken down.
It will also help to lower your blood pressure by keeping your heart and blood vessels in good condition and helping you to lose weight. Being overweight can increase the amount of "bad cholesterol" (LDL) in your blood.
Doing 150 minutes of moderate-intensity exercise every week is recommended to help lower your cholesterol. Find out more about getting more active and achieving your recommended activity levels. Walking, swimming and cycling are all good examples of this kind of exercise.