What is high cholesterol?

What is cholesterol?

Cholesterol (ko-LES-ter-ol) is a fatty substance found in the body. (1) It moves around the body in the blood by attaching itself to proteins, creating molecules known as lipoproteins. (2)

Types of cholesterol

There are two types of cholesterol: low-density lipoprotein (LDL) and high-density lipoprotein (HDL).

These types are often labelled as good and bad respectively. (3) LDL is considered to be harmful to the body; whereas HDL is considered to be protective. (2)

This is because too much LDL can lead to a build-up in the arteries; whereas excess HDL is broken down and removed from the body. (3)

Where is cholesterol found?

Cholesterol is produced by the liver, but it is also found in some foods. (3)

Foods that are particularly high in cholesterol include:

• Kidneys and other offal
• Eggs
• Prawns
• Full fat dairy products
• Meats (4, 5, 6)

Despite cholesterol being found in some foods; it is important to remember that a lot of the cholesterol found in the body actually comes from foods that are high in saturated fat. This is because this fat is turned into cholesterol by the liver. (6)

What does cholesterol do in the body?

The two types of cholesterol do different things in the body. LDL carries cholesterol from the liver to cells that require it; whereas HDL carries cholesterol in the opposite direction – from the cells to the liver. (3)

Cholesterol is also used in the body to make some hormones, vitamin D and some substances that aid digestion. (1)

Specifically, cholesterol is used to make the stress hormones. These are also known as adrenal corticoid hormones and include cortisol, corticosterone and so forth. Cholesterol is also used to make sex hormones: androgens and estrogens. (16)

Cholesterol is used in the making of bile acids, which aid the digestion of food – particularly the digestion of fats. Cholesterol in the bile acid is reabsorped into the intestinal tract once it has been used to break down the fats. Thus, one way of lowering cholesterol levels is to target this reabsorption. (16)

Overall, it is important that your body has cholesterol as these things are essential for the body to function. For example, hormones carry signals around the body. (6)

High cholesterol

Despite cholesterol being important for the body to function, too much cholesterol can be a bad thing.

Video following the life of a man recently diagnosed with high cholesterol. Source: British Heart Foundation

But how high do cholesterol levels have to be to be considered dangerous?

According to the NHS, the UK government states that healthy cholesterol levels are defined as total cholesterol levels below 5mmol/L and LDL levels below 3mmol/L. (7)

The BBC, however, states that healthy cholesterol levels are controversial. (6)

Both the NHS and the BBC stress that healthy levels for people with (or at high risk of) heart disease, hypertension or diabetes should be lower. Specifically they recommend that these high risk individuals should keep their cholesterol levels below 4mmol/L and their LDL levels below 2mmol/L. (6, 7)

How can you tell if you have high cholesterol?

There are not many symptoms of high cholesterol; consequently it may be hard to tell that you have high cholesterol. (8)

One symptom that you may find is yellow patches, called xanthomas, on your skin. These particularly affect the skin around the eye area. (9)

Xanthomas can, however, be caused by other problems, such as diabetes, primary biliary cirrhosis and some cancers. (10)

The main way to tell whether you have high cholesterol is to have a blood test. This may involve fasting for 10-12 hours before the test, to make sure your food does not influence the test. (7)

The blood may be taken either using a needle or syringe or by pricking your finger. (9)

What causes high cholesterol?

The three main things that affect your cholesterol levels are diet, weight and level of physical activity.

If your diet is high in saturated fat, then your blood cholesterol levels will be higher. Similarly, if you are overweight then you are also at a higher risk of high cholesterol.

Physical activity levels can also contribute to your cholesterol levels. Being active for 30 minutes most days can help lower bad cholesterol and raise good cholesterol. (11)

Despite eating a healthy diet, some people may still have high cholesterol. This may be something that they have inherited. There is a condition called familial hyperlipidaemia which is inherited and causes high cholesterol. (2)

What diseases does high cholesterol cause?

High cholesterol makes you more likely to get coronary heart disease. (1)

This is because the LDL can build up inside the coronary arteries, this makes the arteries become narrower. The narrowing of arteries is also known as atherosclerosis. (3)

Atherosclerosis means that blood clots can more easily block the arteries. This can lead to heart attacks. (8)

LDL can also build up in other arteries, such as those that lead to the brain. This can lead to stroke. (1)

High cholesterol can also lead to something that is called a mini-stroke. This is also known as a transient ischaemic attack (TIA). A mini-stroke has similar symptoms to a stroke and is caused by a temporary reduction in the blood supply to the brain. This can be caused by atherosclerosis. (3, 12, 13)

What treatments are there for high cholesterol?

There are several ways that you can lower your cholesterol levels: through a healthy diet; exercising more and taking medications.

Healthy diet

A healthy diet involves lowering your intake of saturated fats, such as:

• Fatty meats
• Meat pies
• Butter
• Cream
• Cakes and biscuits (2, 4)

The Food Standards Agency recommends that men and women eat no more than 30g and 20g of saturated fat per day respectively. (14)

It also involves eating more healthy foods like:

• Oily fish, such as mackerel and salmon
• High-fibre foods such as beans, pulses and lentils
• Fruit and vegetables
• Garlic, cooked or raw
• Foods that contain antioxidants and vitamins C and E, such as strawberries, broccoli and so forth (2, 4, 11)

Exercise

The NHS recommends that you do 150 minutes of moderate-intensity aerobic activity every week. They define this activity as exercise that makes your heart beat faster and causes you to break into a sweat; yet still allows you to be able to talk whilst working. (4)

Medications to lower cholesterol

Some people may need to take medications to lower their cholesterol. Whether this is deemed necessary depends on your LDL and HDL levels, along with your risk of cardiovascular disease. (2)

Video following a man who decides to take statins to lower his cholesterol levels. Source: British Heart Foundation

There are several different medications available to lower cholesterol; these include statins, aspirin, niacin and so forth. (14)

Statins are perhaps the most well-known medicines used to lower cholesterol. They are in fact a group of medicines that include simvastatin, atorvastatin, fluvastatin, pravastatin and rosuvastatin. (9)

They work by blocking an enzyme in your liver that helps make cholesterol.

They can, however, cause side effects including muscle pain and stomach problems, such as indigestion. (9, 14)

Aspirin may be prescribed to prevent blood clots from forming.

Niacin may also be given to lower cholesterol. This is because in high doses it can lower LDL and increase HDL.

Yet again there are potential side effects with this drug. It can lead to liver damage if taken for long periods of time. Also it may cause flushing, which is where the face turns red.

In order to reduce these side effects, it is recommended that you do not take too many niacin supplements and instead try to get as much niacin as you can though your diet. (14)

Several foods contain niacin, which is also known as vitamin B₃. These include:

• Beef, pork and generally foods that are high in protein
• Fish
• Some nuts, including peanuts
• Whole grains (15)

Further Reading

• All Cholesterol Content
• Cholesterol – What is Cholesterol?
• Cholesterol Physiology
• Hypercholesterolemia and Hypocholesterolemia
• High Cholesterol and Stroke Risk

Written by

April Cashin-Garbutt

April graduated with a first-class honours degree in Natural Sciences from Pembroke College, University of Cambridge. During her time as Editor-in-Chief, News-Medical (2012-2017), she kickstarted the content production process and helped to grow the website readership to over 60 million visitors per year. Through interviewing global thought leaders in medicine and life sciences, including Nobel laureates, April developed a passion for neuroscience and now works at the Sainsbury Wellcome Centre for Neural Circuits and Behaviour, located within UCL.