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About high cholesterol
Cholesterol is a fatty substance known as a lipid. It's vital for the normal functioning of the body. Cell membranes, hormones and vitamin D are created by your body using cholesterol.
There are 2 main sources of the cholesterol in your blood:
- cholesterol in the food you eat
- cholesterol produced by your liver
Having an excessively high level of lipids in your blood (hyperlipidemia) can have an effect on your health.
High cholesterol, on its own, doesn't usually cause any symptoms but increases your risk of serious health conditions.
Cholesterol is carried in your blood by proteins. When the two combine, they're called lipoproteins. There are two main types of lipoprotein.
High-density lipoprotein (HDL) carries cholesterol away from the cells and back to the liver. From there it's either broken down or passed out of the body as a waste product. For this reason, HDL is referred to as "good cholesterol" and higher levels are better.
Low-density lipoprotein (LDL) carries cholesterol 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 is known as "bad cholesterol".
The amount of cholesterol in the blood, both HDL and LDL , is measured with a blood test.
The recommended cholesterol levels in the blood vary between those with a higher or lower risk of developing arterial disease.
Why should I lower my cholesterol?
Evidence strongly indicates that high cholesterol can increase the risk of:
- narrowing of the arteries (atherosclerosis)
- heart attack
- transient ischaemic attack (TIA) – often known as a "mini stroke"
- peripheral arterial disease (PAD)
This is because cholesterol can build up in the artery wall, restricting the blood flow to your heart, brain and the rest of your body. It also increases the risk of a blood clot developing somewhere in your body.
Your risk of developing coronary heart disease also rises as your blood's cholesterol level increases. This can cause pain in your chest or arm during stress or physical activity (angina).
What causes high cholesterol?
Many factors can increase your chances of having heart problems or a stroke if you have high cholesterol.
- an unhealthy diet – in particular, eating high levels of saturated fat
- smoking – a chemical called acrolin, found in cigarettes, stops HDL transporting cholesterol from fatty deposits 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 called familial hypercholesterolaemia. This can cause high cholesterol even in someone who eats healthily.
Read more about the causes of high cholesterol
When should my cholesterol levels be tested?
Your GP 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)
- 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
Read more about how cholesterol is tested
What should my cholesterol levels be?
Blood cholesterol is measured in units called millimoles per litre of blood, often shortened to mmol/L.
As a general guide, total cholesterol levels should be:
- 5mmol/L or less for healthy adults
- 4mmol/L or less for those at high risk
As a general guide, LDL levels should be:
- 3mmol/L or less for healthy adults
- 2mmol/L or less for those at high risk
An ideal level of HDL is above 1mmol/L. A lower level of HDL can increase your risk of heart disease.
Your ratio of total cholesterol to HDL may also be calculated. This is your total cholesterol level divided by your HDL level. Generally, this ratio should be below four, as a higher ratio increases your risk of heart disease.
Cholesterol is only one risk factor. The level at which specific treatment is required will depend on whether other risk factors, such as smoking and high blood pressure, are also present.
How can I lower my cholesterol level?
The first step in reducing your cholesterol is to maintain a healthy, balanced diet. It's important to keep your diet low in fatty food.
You can swap food containing saturated fat for fruit, vegetables and wholegrain cereals. This will also help prevent high cholesterol from returning.
Other lifestyle changes, such as taking regular exercise and giving up smoking, can also make a big difference in helping to lower your cholesterol.
If these measures don't reduce your cholesterol and you continue to have a high risk of developing heart disease, your GP may prescribe a cholesterol-lowering medication, such as statins.
Your GP will take into account the risk of any side effects from statins. The benefit of lowering your cholesterol must outweigh any risks.
Causes of high cholesterol
Many different factors can contribute to high blood cholesterol, including lifestyle factors like smoking, an unhealthy diet and lack of exercise, as well as having an underlying condition, such as high blood pressure or diabetes.
Your lifestyle can increase your risk of developing high blood cholesterol.
- an unhealthy diet – some foods, such as liver, kidneys and eggs, contain cholesterol (dietary cholesterol), but this has little effect on blood cholesterol: it's the total amount of saturated fat in your diet that's more important to watch; read more about preventing high cholesterol
- lack of exercise or physical activity – this can increase your level of "bad cholesterol" (low-density lipoprotein, or LDL)
- obesity – if you're overweight, it's likely that you'll have higher levels of LDL cholesterol and triglycerides, and a lower level of high-density lipoprotein (HDL)
- drinking excessive amounts of alcohol – regularly drinking large amounts of alcohol can increase your cholesterol and triglyceride levels
- smoking – a chemical in cigarettes called acrolein stops "good cholesterol" (HDL) transporting cholesterol from fatty deposits to the liver, leading to narrowing of the arteries (atherosclerosis)
People with high blood pressure (hypertension) and diabetes often have high cholesterol.
Some other health conditions that can also cause raised levels of cholesterol include:
- kidney disease
- liver disease
- an underactive thyroid gland (hypothyroidism)
Treating the underlying condition can help to reduce cholesterol.
There are a number of factors associated with high cholesterol that can't be changed that increase your risk of having a heart attack or stroke. Doctors refer to these as "fixed factors".
- family history of early coronary heart disease (CHD) 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's had CHD or stroke
- a family history of a cholesterol-related condition – for example, having a parent, brother or sister with familial hypercholesterolaemia
- age – the older you are, the greater the likelihood of your arteries narrowing (atherosclerosis)
- ethnic group – people of Indian, Pakistani, Bangladeshi and Sri Lankan descent are at increased risk of having a heart attack
- sex – males are more likely to have heart attacks than females
If you have a fixed risk factor, or several fixed risk factors, it's even more important to look at your lifestyle and any underlying conditions you may have.
Familial hypercholesterolaemia is the medical term for high cholesterol that runs in families. It's caused by a gene alteration inherited from a parent, rather than an unhealthy lifestyle.
People with familial hypercholesterolaemia have raised cholesterol from birth, which can lead to the early development of heart problems, such as atherosclerosis and CHD.
In the UK, familial hypercholesterolaemia is thought to affect about 1 in 500 people, which means approximately 120,000 people are thought to be affected.
There's a one in two (50%) chance that a child or brother or sister of someone with familial hypercholesterolaemia will also have the condition.
Read more about the importance of early identification and diagnosis of familial hypercholesterolaemia
Diagnosing high cholesterol
Blood cholesterol levels are measured with a simple blood test.
Getting a cholesterol test
A blood sample is taken that will be used to determine the amount of bad cholesterol (low-density lipoprotein, or LDL), good cholesterol (high-density lipoprotein, or HDL) and other fatty substances (triglycerides) in your blood.
You may be asked not to eat for 10-12 hours before the cholesterol test, usually including when you're asleep at night. This ensures that all food is completely digested and won't affect the outcome of the test.
Your GP or practice nurse can carry out the cholesterol test and will take a blood sample, either using a needle and a syringe or by pricking your finger.
A newer type of test that measures non-high-density lipoprotein (non-HDL) is now sometimes used because it's thought to be a more accurate way of estimating cardiovascular disease (CVD) risk than LDL.
Non-HDL cholesterol is total cholesterol minus HDL cholesterol. It's also not necessary to fast before the test, so it is more convenient.
Who should be tested?
Your GP 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 the age of 40 – people over 40 should have their estimate of CVD risk reviewed regularly
- 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
- are overweight or obese
- have high blood pressure or diabetes
- have another medical condition, such as kidney disease, an underactive thyroid, or an inflamed pancreas (pancreatitis) – these conditions can cause increased levels of cholesterol or triglycerides
After your cholesterol test, your GP or nurse will explain your results and calculate whether you have a high, moderate or low risk of developing heart disease or stroke (cardiovascular disease) within the next 10 years.
However, this risk isn't just based on your cholesterol reading. It also takes into account:
- 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
Based on your results, your GP or nurse will recommend steps you can take to reduce your risk of developing CVD.
This may include advice about making lifestyle changes, such as eating more healthily – by increasing your intake of omega-3 fatty acids, for example – and doing more exercise.
Cholesterol-lowering medication, such as statins, may also be recommended.
Read more about treating high cholesterol
People with familial hypercholesterolaemia, or inherited high cholesterol, are at increased risk of developing CVD.
In the UK, most of the 120,000 people thought to have the condition are undiagnosed and untreated.
As a result of the increased risk of developing CVD, it's very important that those with familial hypercholesterolaemia are diagnosed as early as possible and offered appropriate treatment.
The National Institute for Health and Care Excellence (NICE) recommends that adults with a total cholesterol level of above 7.5mmol/l before treatment should be assessed for familial hypercholesterolaemia.
If you've been diagnosed with familial hypercholesterolaemia, you'll be referred for a specialist assessment, which may include DNA testing to confirm the diagnosis.
Appropriate treatment will be recommended and other members of your family who may be affected will also be tested.
You'll be closely monitored, and should have a full review at least once a year to check how well your treatment is working and assess any symptoms you may have.
Children at risk of familial hypercholesterolaemia will be tested by the time they reach 10 years of age.
This is because any signs of CVD, such as thickening of the carotid artery wall, will be identifiable by this age.
The assessment will be carried out by a specialist with expertise in familial hypercholesterolaemia in children and young people.
Early diagnosis of familial hypercholesterolaemia means it's possible to recommend lifestyle changes and other appropriate treatments to reduce the long-term problems associated with high cholesterol and improve long-term health.
For further information, see the NICE guidance about familial hypercholesterolaemia
Treating high cholesterol
If you've been diagnosed with high cholesterol, you'll 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 may be advised to take cholesterol-lowering medication.
Changing your diet, stopping smoking and exercising more will also help to prevent high cholesterol developing.
The various treatments for high cholesterol are outlined below.
Eating a healthy, balanced diet that's low in saturated fats can reduce your level of "bad cholesterol" (LDL).
Try to avoid or cut down on the following foods, which are high in saturated fat:
- fatty cuts of meat and meat products, such as sausages and pies
- butter, ghee and lard
- cream, soured cream, crème fraîche and ice cream
- cheese, particularly hard cheese
- cakes and biscuits
- milk chocolate
- coconut oil, coconut cream and palm oil
The government recommends that a maximum of 11% of a person's food energy should come from saturated fat. This equates to no more than:
- 30g of saturated fat a day for the average man
- 20g of saturated fat a day for the average woman
Children should have less.
Check the labels on the foods you're eating to find out how much saturated fat you're consuming.
Omega-3 fatty acids
Many experts believe that the fats found in avocados and 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 people. However, too much omega-3 fatty acids can contribute to obesity.
For people with a high triglyceride level, at least two portions of oily fish a week is thought to be beneficial. However, there's no evidence that taking omega-3 fatty acid supplements has the same benefit.
There are several different types of cholesterol-lowering medication that work in different ways. Your GP can advise you about the most suitable type of treatment, and 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 to make cholesterol. This leads to a reduction in your blood cholesterol level.
You'll usually be started on a medication called atorvastatin. Other statins include simvastatin and rosuvastatin.
When someone has side effects from using a statin, it's described as having an "intolerance" to it. Side effects of statins include headaches, muscle pain and stomach problems, such as indigestion, diarrhoea or constipation.
Statins will only be prescribed to people who continue to be at high risk of heart disease, because they need to be taken for life. 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 (usually over 40 years old) and other risk factors.
Low-dose aspirin can help to prevent blood clots forming, particularly for someone who's had a heart attack, has established vascular disease, or a high risk of developing cardiovascular disease (CVD).
You may also be advised to have periodic blood tests to ensure your liver is functioning well.
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 cause side effects.
You can take ezetimibe at the same time as your usual statin if your cholesterol levels aren't low enough with the statin alone. The side effects of this combination are generally the same as those of the statin on its own (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, 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.
For more information, you can read the National Institute for Health & Care Excellence (NICE) guidelines about the use of ezetimibe for treating high cholesterol.
Preventing high cholesterol
You can lower your cholesterol by eating a healthy, balanced diet that's low in saturated fat, exercising regularly, not smoking and cutting down on alcohol.
If you have an unhealthy diet that's high in fat, fatty plaques are much more likely to build up in your arteries. This is because fatty foods contain cholesterol.
There are two types of fat: saturated and unsaturated. You should avoid foods containing saturated fats, as they will increase the levels of "bad cholesterol" (low-density lipoprotein, or LDL) 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
However, it's not healthy to completely cut out all types of fat from your diet. It's important to replace saturated fats with unsaturated fats – they've been shown to increase levels of "good cholesterol" (high-density lipoprotein, or HDL) and reduce any blockage in your arteries.
Foods that are high in unsaturated fat include:
- oily fish – such as mackerel, salmon and tuna
- nuts and seeds
- sunflower, rapeseed and olive oil
A low-fat diet including lots of fibre, such as wholegrain rice, bread and pasta, and plenty of fruit and vegetables has also been shown 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 five 80g portions of fruit and vegetables every day.
A chemical found in cigarettes called acrolein stops HDL transporting fatty deposits to the liver, leading to high cholesterol and narrowing of the arteries (atherosclerosis). This means smoking is a major risk factor for both heart attacks and strokes.
If you decide to stop smoking, your GP can refer you to an NHS Stop Smoking Service, which will provide you with dedicated help and advice about the best ways to give up smoking.
You can also call Quit Your Way Scotland on 0800 84 84 84. The specially trained helpline staff can offer you free expert advice and encouragement.
If you're committed to giving up smoking but don't want to be referred to a stop smoking service, your GP should be able to prescribe medical treatment to help with any withdrawal symptoms you may experience after giving up.
Read more about treatment for quitting smoking
Being active and exercising regularly will increase the levels of HDL in your body by stimulating the body to move fatty deposits to the liver, so they can be broken down.
Exercise will also help you maintain a healthy weight, and lose weight if you're overweight. Being overweight can increase the amount of "bad cholesterol" in your blood.
Another benefit of regular physical activity is it will help lower your blood pressure by keeping your heart and blood vessels in good condition.
Doing 150 minutes of moderate-intensity exercise every week is recommended to help lower your cholesterol. Walking, swimming and cycling are good examples of this type of exercise.
Read more about the recommended physical activity guidelines for adults (aged 19-64) and the physical activity guidelines for older adults (aged 65 and over)
19 January 2023
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