Cholesterol is carried around your body by a protein in your blood. This combination of fat and protein is called a lipoprotein. There are different types of lipoprotein, and they may be harmful or beneficial to your health.
High-density lipoprotein (HDL)
High-density lipoprotein (HDL) helps to get rid of excess cholesterol from your blood vessels. It does this by carrying cholesterol from your tissues (including the walls of arteries) to your liver. Your liver then breaks down the cholesterol so your body can get rid of it. As HDL helps prevent cholesterol building up in your blood vessels, it helps to reduce your risk of heart disease and stroke. This is why HDL is often referred to as ‘good’ cholesterol.
Low-density lipoprotein (LDL)
Low-density lipoprotein (LDL) carries cholesterol from your liver to the cells around your body where it’s needed. But if the level of LDL in your blood is too high, it can form fatty deposits in your arteries. This increases your risk of heart disease and stroke. For this reason, LDL is often called ‘bad’ cholesterol.
High cholesterol doesn’t cause any symptoms itself. But if you have it, it can lead to serious problems affecting your heart and circulation, such as heart attack and stroke. You may start to develop symptoms of heart disease such as angina (chest pain). See your GP if you notice any symptoms like this.
Your cholesterol level can be measured with a simple blood test. Your doctor or nurse may take a blood sample using either a needle and syringe, or a finger prick.
The amount of cholesterol in your blood is measured in units called millimoles per litre of blood, usually shortened to ‘mmol/L'. There are different types of cholesterol in your blood, and your blood test will show how much of each type you have. High-density lipoprotein (HDL) helps to protect your body from heart disease and stroke, while low-density lipoprotein (LDL) increases your risk.
Your doctor will look at your total cholesterol level and how much HDL you have compared to your total cholesterol (this is called your total cholesterol to HDL cholesterol ratio). The blood test will also measure the levels of another type of fat in your blood, called triglycerides. A high level of triglycerides is also a risk factor for heart disease and stroke.
The levels of cholesterol in your blood can vary from day to day, so your doctor may want to repeat the test before recommending any treatment.
Who should have a cholesterol test?
You may be offered a cholesterol test if you:
- have certain risk factors for heart disease and stroke such as high blood pressure, type 2 diabetes or are overweight
- are over the age of 40
- have a family history of high cholesterol (known as familial hypercholesterolaemia)
- have already been diagnosed with heart disease or stroke
- have yellow patches around your eyes or on your skin (these are known as xanthoma and can be a sign of high cholesterol)
Your cholesterol level may be measured as part of a wider assessment to check your risk of developing heart disease and stroke. This will also include checking other factors, such as your weight and your blood pressure. Your GP will use the results from all these tests to calculate your risk of having a heart attack or stroke.
You’re said to be high risk if your risk of heart disease or stroke is more than 10 percent over the next 10 years. This means that of 100 people with similar risk factors to you, more than 10 would have a heart attack or stroke in the next 10 years.
If you’re classed at being at high risk of having heart disease or stroke, your doctor will recommend you take steps to lower your cholesterol level. There’s no specific cholesterol level that means you’ll be offered treatment, as your risk depends on lots of other factors. These include smoking and being overweight.
To begin with, your GP will recommend some lifestyle changes you can make in order to reduce your risk of heart attack and stroke. These may include:
- reducing the fat in your diet, particularly saturated fats (eg from biscuits, cakes, pastries, red meat, hard cheese and butter)
- reducing the amount of cholesterol in your diet (eg from eggs, prawns and offal)
- making other changes to your diet – such as eating more fruit and vegetables, and oily fish
- doing more physical activity
- losing any excess weight
- making sure you don’t drink more than recommended alcohol limits
- stopping smoking if you smoke
The main group of medicines for lowering cholesterol are called statins. Statins used in the UK include atorvastatin and simvastatin. Your GP may recommend you take a statin if changes to your lifestyle haven’t reduced your cholesterol level enough. There are some other instances when you’ll be offered statins. These include if you’re 85 or older, have type I diabetes, kidney disease or if you’ve already had a heart attack or stroke.
Your GP will usually ask to check your cholesterol level again around three months after you’ve started treatment, to see how well it’s working. If you don’t get on with your treatment, or it’s not working very well, your doctor may suggest reducing the dose or trying another statin. It’s your choice whether or not to take statin tablets. Your doctor will discuss the risks and benefits of taking statins with you before you start any treatment, to help you to make a decision.
If statins aren’t helping to lower your cholesterol level, your GP may refer you to a cardiologist for further treatment. A cardiologist is a doctor specialising in conditions affecting the heart. You may be offered a medicine called ezetimibe to take as well as your statin.
High cholesterol is often caused by a number of factors, which all act to increase your cholesterol level. These may include:
- having a diet high in saturated fat, cholesterol and trans fats
- not doing much exercise
- being overweight or obese
- drinking too much alcohol
Sometimes, high cholesterol can be caused by a condition that runs in your family called familial hypercholesterolaemia. This means you may have a very high cholesterol level, even if you have a healthy lifestyle. In the UK, about one in 500 people have this condition. Other conditions, such as poorly controlled diabetes, certain kidney and liver diseases and underactive thyroid (hypothyroidism) may also cause high cholesterol. Some medicines can also raise your cholesterol, such as the oral contraceptive pill, beta-blockers and thiazides (a type of medicine to reduce your water level).
High cholesterol increases your risk of heart disease and stroke. This is because the cholesterol in your blood can form fatty deposits, known as plaques, in the walls of your arteries. If the plaque bursts, it can cause a blood clot. This could cause a heart attack if the clot blocks an artery to your heart. It may cause a stroke if it blocks the artery to your brain.
The arteries elsewhere in your body, such as your legs, may also be affected. This is known as peripheral arterial disease.
You can help to keep your cholesterol level low by keeping to a healthy weight and eating a diet that’s low in saturated fat, trans fats and cholesterol. Foods high in saturated fats include fatty meat (particularly red meat), biscuits, cakes and pastries. Trans fats are found in processed foods, such as cakes and biscuits. Try to replace these in your diet with foods that contain unsaturated fats – such as nuts and olive oil.
It also helps to take regular exercise, stop smoking if you smoke, and stick to recommended limits of alcohol.
How do the fats in my food affect my cholesterol levels?
It’s important to have some fats in your diet. But eating too much of the wrong types of fat increases your cholesterol levels, which can increase your risk of heart disease and stroke.
Some fat is an essential part of a healthy diet. But it's important that you're careful about the type of fat that you eat and that you don't eat too much of it. Eating certain types of fat can increase the amount of cholesterol your liver produces. A high level of low-density lipoprotein (LDL) cholesterol can increase your risk of heart disease and stroke.
These are the different types of fat in the food we eat.
- Saturated fats – these increase your cholesterol levels. Examples of foods high in saturated fats include cakes and biscuits, pastry, meat products and hard cheese.
- Trans fats – these have a similar effect on your cholesterol levels as saturated fats. Foods containing hydrogenated vegetable oil (which must be listed in the ingredients list on the label) might contain trans fats. Trans fats currently don't need to be labelled separately on food labels. They can be found in biscuits and cakes, fast food and some margarines.
- Monounsaturated fats – these help lower harmful cholesterol levels. Examples of foods high in monounsaturated fats include olive oil, avocado and nuts (eg, almonds, cashews, peanuts and pistachios).
- Polyunsaturated fats – these lower both harmful and protective cholesterol levels. Examples of foods high in polyunsaturated fats include sunflower oil, oily fish, and nuts and seeds (eg, walnuts, pine nuts, sesame and sunflower seeds).
When you're shopping for food, compare the labels so you can pick those with less total fat or less saturated fat. Aim to replace saturated fats in your diet with monounsaturated or polyunsaturated fats whenever you can. This may mean using olive or rapeseed oil to cook with rather than lard or butter, and using spreads based on these oils. Try to go for lower fat versions of dairy foods, such as semi-skimmed or skimmed milk, and reduced-fat yoghurt.
There’s a particular type of polyunsaturated fat called omega-3 which can help to reduce your cholesterol levels. The best source of omega-3 fats is oily fish, such as kippers, mackerel, sardines and salmon. Try to eat two portions of fish per week, including a portion of oily fish. But don’t have more than two portions per week if you're pregnant or breastfeeding.
Are all statins the same?
There are several different types of statin available in the UK. They vary in how well they work at reducing cholesterol. Your doctor will prescribe you a statin at a dose that is suitable for reducing your cholesterol levels, with as few side-effects as possible.
There are different types of statin available in the UK. Examples include simvastatin, atorvastatin, and fluvastatin. All statins work in the same way, but have different chemical structures. Statins lower the level of cholesterol in your blood, especially low-density lipoprotein (LDL) or 'bad' cholesterol. Having a low cholesterol level reduces your risk of heart disease, including heart attacks.
If you need to take a statin, you will usually be prescribed atorvastatin to try first. Your cholesterol levels will be checked regularly and if necessary, your doctor may adjust the dose of your statin.
As with any medicine, you may have some side-effects when taking statins, but these are generally mild and similar for all types of statin. Your doctor will monitor possible side-effects by doing a liver function blood test before you start taking the statin and again a few months later. If your liver function is affected, you may need to take a different statin.
What is a normal cholesterol level?
There’s no set recommended target cholesterol level. Generally, the lower your cholesterol, the better.
The average total cholesterol level for adults in the UK is around 5mmol/L. However, there’s no recommendation for the ideal level of cholesterol – the lower your cholesterol level, the better.
Whether or not you need treatment to lower your cholesterol level depends on your overall risk of having a heart attack or stroke. Your doctor will look at several factors to calculate this risk, not just your cholesterol level. These include your age, sex, body mass index (BMI), blood pressure, family history and whether you smoke or drink alcohol. If you have any other illnesses such as diabetes, this will also be taken into account. This means you may be offered treatment to reduce your cholesterol, even if your cholesterol level is lower than someone who doesn’t need treatment.
If you’re prescribed a statin, your GP will be aiming to lower your cholesterol level by at least 40 per cent, no matter what your cholesterol level. For example, this could mean a reduction from 7.5mmol/L to 4.5mmol/L. Any reduction in cholesterol helps to lower your risk of heart disease and stroke.
Can sterols and stanols help to reduce my cholesterol?
It’s possible that products containing plant sterols and stanols may help to reduce your levels of LDL (low-density lipoprotein) cholesterol. However, there’s no evidence that sterols and stanols reduce your risk of heart disease and stroke. They aren’t recommended as a treatment to lower cholesterol in people who are at high risk of heart disease and stroke.
Plant sterols and stanols are often added to certain food products, including certain spreads, yoghurts and mini-drinks. There’s some evidence that regularly consuming these products can help to reduce your level of LDL cholesterol. This is the ‘bad’ cholesterol in your blood that can cause the build up of fatty plaques in your arteries. However, there’s no evidence yet to prove that taking them also reduces your risk of heart attack and stroke.
It’s your choice whether or not to try sterols and stanols. They’re not recommended for people who have been advised to reduce their risk of heart disease and stroke. Making lifestyle changes, such as reducing the fat in your diet, and taking cholesterol-lowering medicines, such as statins, are proven ways of reducing your cholesterol. If you do decide to try taking sterols or stanols, you should still aim to make any lifestyle changes or take any medicines that your doctor advises.
You shouldn’t take products containing sterols and stanols if you’re pregnant or breastfeeeding, and they’re not suitable for children under the age of 5.
- Cardiology and vascular disease. Oxford handbook of general practice (online). Oxford Medicines Online. www.oxfordmedicine.com, April 2014
- Atherosclerosis. The Merck Manuals. www.merckmanuals.com, published September 2012
- Overview of lipid metabolism. The Merck Manuals. www.merckmanuals.com, published October 2013
- Dyslipidemia. The Merck Manuals. www.merckmanuals.com, published October 2013
- Reducing your blood cholesterol. British Heart Foundation, January 2014, www.bhf.org.uk
- Lipid modification: cardiovascular risk assessment and the modification of blood lipids for the primary and secondary prevention of cardiovascular disease. National Institute for Health and Care Excellence (NICE), July 2014. www.nice.org.uk
- Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. www.medicinescomplete.com, accessed 28 November 2014
- Ezetimibe for the treatment of primary (heterozygous-familial and non-familial) hypercholesterolaemia. National Institute for Health and Care Excellence (NICE), November 2007. www.nice.org.uk
- Fats – getting the balance right. British Dietetic Association. www.bda.uk.com, published January 2012.
- Cholesterol-lowering sterols and stanols. Patientplus. www.patient.co.uk , published 29 August 2014
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Reviewed by Pippa Coulter, Bupa Health Information Team, December 2014.
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