Basics in Cholesterol

What is cholesterol?
The Cholesterol Transport System
What’s the difference between ‘bad’ and ‘good’ cholesterol?
How can high cholesterol affect heart health?
How many people have high cholesterol?
What are the symptoms of high cholesterol?
How is cholesterol tested?
Cholesterol levels – What do the results of a cholesterol test mean?
What causes high cholesterol?
How can I reduce my cholesterol?

What is cholesterol?

Cholesterol is a wax-like, fatty substance that’s sometimes called a blood fat because it circulates in our blood. It’s an essential part of every cell in our body and has many important functions. For example, it’s used as a building block to make hormones such cortisol, testosterone and progesterone. It’s used to make bile acids, which help to digest fat. And it’s a component of vitamin D. However, if too much cholesterol circulates in the blood, this can affect the risk of coronary heart disease.

Where does cholesterol come from?

A small amount of cholesterol comes from the foods we eat. However, most of the cholesterol in our body is made by the liver, using saturated fat as the building blocks. Our liver is also responsible for controlling the amount of cholesterol that circulates in our blood and distributing it to the areas that need it.

The Cholesterol Transport System

How does cholesterol travel around the body?

In a similar way that we use roads to get from one place to another, cholesterol uses the blood as its transport system. It can’t travel on its own though, so it attaches itself to ‘vehicles’ made up of proteins. These combos of cholesterol and proteins are called lipoproteins (lipo comes from the Greek word for fat). In this way, cholesterol is transported around the body and deposited at various points where it’s needed, a little like cars and buses drop off passengers at different locations. There are two main groups of lipoproteins:

1. Non-high density lipoproteins (non-HDL) – or ‘bad’ cholesterol = LDL
2. High-density lipoproteins (HDL) – often called ‘good’ cholesterol.

What’s the difference between ‘bad’ and ‘good’ cholesterol?

LDL or ‘bad’ cholesterol

LDL lipoproteins transport cholesterol from the liver to destinations that need it, such as cells and tissues. However, if the smooth surface of the transport system – the arteries – are damaged, LDL can lose some of its cholesterol along the way. It’s a bit like driving down a bumpy road, which results in you losing a package from your vehicle. The more traffic there is on the road, the more opportunity there is for packages to be discarded on route, too. In other words, when LDL levels are raised, there’s a greater chance that cholesterol will be deposited in the arteries. Over time, this cholesterol can start to build up in the arteries and combine with other substances to form a fatty plaque known as an atheroma in the artery walls. This causes the arteries to narrow and harden – a process known as atherosclerosis. This means blood flows less easily around the body and our heart has to work harder to pump it around. That’s why LDL is called ‘bad’ cholesterol.

HDL or ‘good’ cholesterol

HDL lipoproteins carry excess cholesterol away from the arteries and take them to the liver. Here, cholesterol is broken down and then eliminated from the body. Higher HDL levels mean there’s more traffic available to pick up cholesterol from cells and take it back to base, removing it from the transport system before it has a chance to build up in the arteries. As a result, high HDL levels are good news for overall blood cholesterol, and coronary heart disease risk and the reason why HDL is called ‘good’ cholesterol.

What is LDL cholesterol?

LDL cholesterol belongs in the group of non-HDL cholesterol. Until recently, LDL was used as the main measure for ‘bad’ cholesterol but it’s now known there are other forms of cholesterol that are bad for us, too. Cholesterol is now divided into the following two groups:

1. Non-HDL or ‘bad’ cholesterol – this includes LDL and all other forms of ‘bad’ cholesterol added together
2. HDL or ‘good’ cholesterol

What are triglycerides?

Triglycerides are another type of fat that are transported in the blood using lipoproteins. These fats provide energy to cells and tissues. If our energy needs are met, excess triglycerides are stored in fat cells until they’re needed.

Triglycerides in the blood are usually measured at the same time as cholesterol. It’s important to measure them because raised levels can increase the risk of heart and circulatory diseases, especially coronary heart disease and stroke.

Triglyceride levels tend to be higher in people who are overweight, inactive, have Type 2 diabetes or metabolic syndrome, eat a diet high in fatty and sugary foods and drink too much alcohol. The good news is, diet and lifestyle changes that help to reduce cholesterol will also help to reduce triglycerides.

Did you know?

• If you hear your doctor talking about ‘blood lipids’ this is simply the name for all the fatty substances found in the blood, including HDL cholesterol, non-HDL cholesterol and triglycerides.
• When people talk about high cholesterol, they’re usually referring to high levels of ‘bad’ cholesterol.

How does high cholesterol affect heart health?

High cholesterol is one of the main risk factors for cardiovascular disease (CVD), a general name for all diseases of the heart and circulation. It is recommended that everyone over 40 should have their cholesterol levels checked to ensure cholesterol levels are within a healthy range. [1]

Other things that increase the risk of CVD include:

• high blood pressure
• smoking
• being overweight
• inactivity
• drinking alcohol to excess
• not eating enough fruit and vegetables
• having type 2 diabetes
• a family history of CVD
• being older, male

Cardiovascular disease is amongst the leading causes of death in Ireland. (2)

Cardiovascular disease (CVD) covers a range of conditions, including those that people are born with or inherit, through to those that typically occur later in life such as coronary heart disease, strokes and peripheral artery disease. Below is some of the Coronary heart disease (CHD) one type of CVD.

Coronary heart disease (CHD)

• Almost three quarters of Irish adults suffer from two or more chronic or cardiovascular medical conditions (hypertension, angina, high cholesterol, heart failure) (3)
• Across all ages and genders, 1 in 10 of the Irish population has high cholesterol. [4]
• Heart disease and stroke, recorded by the CSO as “diseases of the circulatory system” are responsible for 29% of total deaths in Ireland [5]

Of all the diseases of the heart and circulation, CHD is the most common. A high level of ‘bad’ cholesterol is one of the main risk factors for CHD – when cholesterol builds up in the arteries, causing them to narrow and harden, it’s harder for the blood to flow easily through them. This means the heart has to work harder to pump blood around the body. Over time, this can weaken the heart so it doesn’t work as well as it should. If blood flow is restricted, it can also make it harder to deliver enough oxygen to our organs, a condition doctors sometimes refer to as ischaemia.

CHD can sometimes lead to several common conditions such as:

• Angina
• Heart attack
• Heart failure

How many people have high cholesterol?

Findings from the Healthy Ireland Summary Report show that at least a fifth of males and females over 55 years have high cholesterol. (4) However, the amount of people with raised total cholesterol has declined over time. According to the World Health Organisation (WHO), in Ireland, a 30% decline in heart disease death rate has been attributed to a 4.6% reduction of the population’s total cholesterol. (6) Although this is a move in the right direction, there are still a huge number of people with cholesterol levels that are too high, putting them at risk of conditions such coronary heart disease. Meanwhile, anyone can be a victim of high cholesterol!

Myth buster: Only elderly people suffer with high cholesterol

It’s true that as we move through the decades towards retirement age, the more likely we are to have raised total cholesterol. Data from the Central Statistics Office (CSO) showed that diseases of the circulatory system accounted for almost a quarter of deaths in those aged between 35 – 75 years. In addition, 7% of deaths those aged 15-34 were due to diseases of the circulatory system.(5) Bottom line: a large number of young people also have cholesterol levels that are too high and so are putting their health at risk.

Myth buster: High cholesterol is mainly a problem for men

High cholesterol doesn’t just affect men – women are also at risk and in some cases, even more so than men! In fact, figures show that slightly more young women aged 25 to 34 years have raised total cholesterol than men of the same age. This is the same for adults aged above 55 years. For example, 23% of women aged 55 to 64 years have high cholesterol compared to 20% of men in the same age category. (4) The reality: women need to be just as vigilant at getting their cholesterol levels monitored, especially after the menopause.

Source: Healthy Ireland Summary Report 2019

What are the symptoms of high cholesterol?

High cholesterol usually has no visible or obvious symptoms making it a hidden health hazard sometimes known as the ‘silent killer!’ Most people aren’t aware they have high cholesterol until they start suffering with symptoms like chest pain or breathlessness linked to specific heart conditions. That’s why it’s so important to get cholesterol levels checked.

Did you know?

Optometrists can sometimes spot the warning signs that point to the presence of high cholesterol during a routine eye test.

They are able to detect abnormalities in parts of the eye such as the retina or cornea that could indicate a possible problem with cholesterol. If they spot any such signs, they may recommend you have a cholesterol test and inform your GP of their findings.

Myth buster: Only overweight and unfit people have high cholesterol

This is simply not true. While being overweight and inactive tend to go hand in hand with high cholesterol, being a healthy weight and exercising regularly aren’t an automatic green light for healthy levels of cholesterol. The truth is even slim, fit people can have high cholesterol. That’s why it’s so important to get your cholesterol checked.

How is cholesterol tested?

Blood cholesterol levels are easily checked with a finger prick test or by taking a sample of blood from your arm. The easiest way to arrange this is through your doctor’s surgery or health centre. If a sample of blood is taken, it will be sent to a lab and you should get the results within a few days. You may be asked not to eat anything for up to 12 hours beforehand (this is known as a fasting blood test) although this isn’t usually necessary. A finger prick test is done by pricking your finger and putting a drop of blood onto a strip of paper, which then goes into a machine and checks your cholesterol within a few minutes.

Many pharmacies offer cholesterol tests, although you might have to pay for them. You can also buy home-testing cholesterol kits from shops or online but these may not be as reliable as a cholesterol test carried out by a health professional. It’s always better to contact your surgery or health centre and arrange a cholesterol test through them.

Cholesterol levels – What do the results of a cholesterol test mean?

A cholesterol test usually measures:

• Total cholesterol – this is the total amount of cholesterol in the blood and includes both ‘good’ and ‘bad’ cholesterol. It’s sometimes called ‘serum cholesterol’ or ‘TC’
• HDL or ‘good’ cholesterol – the higher the better
• Non-HDL or ‘bad’ cholesterol – the lower the better
• Triglycerides – the lower the better
• Total cholesterol to HDL ratio – this is often written as TC:HDL and is a value that looks at the proportion of HDL in relation to total cholesterol – the lower the better.

Components of cholesterol are measured in units called millimoles per litre of blood (mmol/L). As a guide, these are the values healthy adults should aim for [7]

Total cholesterol	Below 5
Non-HDL or ‘bad’ cholesterol	Below 4
LDL cholesterol	Below 3
HDL or ‘good’ cholesterol	Above 1 for men and 1.2 for women
TC:HDL ratio	The lower the better – above 6 is considered a high risk
Triglycerides	Below 2.3 (non-fasting) Below 1.7 (fasting)

It’s important to realise these values are only a guide and your doctor or nurse may recommend different levels for you, depending on other risk factors you have such as smoking or being overweight, and other medical conditions such as type 2 diabetes.

When you get the results of your blood test, you may only be given the value for total cholesterol, but you can always ask for the values for ‘good’ and ‘bad’ cholesterol, as well as triglycerides.

If your cholesterol or triglyceride levels come back as being high, your GP will advise on next steps. This may include offering you help and advice on making changes to your diet and lifestyle, as well as possibly prescribing medication to lower cholesterol.

Although high levels of ‘bad’ cholesterol are a risk factor for cardiovascular disease (CVD), it’s important to realise they are only one part of the picture. Smoking, lack of exercise, being overweight, having high blood pressure or type 2 diabetes and a strong family history will all affect your risk, too – and the more of these risk factors you have, the greater your chance of suffering with CVD. Learn more about cholesterol levels.

Who should have a cholesterol test?

Your GP will normally suggest having a cholesterol test if they think you might be at risk of high levels. This may be because you have a family history of CVD or other risk factors such as high blood pressure, type 2 diabetes or are overweight.

What causes high cholesterol?

People of any age, gender or ethnic background can have high cholesterol. Certain medical conditions such as hypothyroidism (an underactive thyroid gland), kidney or liver disease, a family history of high cholesterol and being born with a genetic condition called familial hypercholesterolemia may also put us at risk. These are all things we have no control over. Meanwhile, some medications can increase the risk, which your doctor can advise on.

However, many of our everyday habits can also leave us with high cholesterol – and these are things we have the ability to change. To help achieve and maintain cholesterol within healthy limits, the key is to focus on those things we can control. The good news is there are plenty of things we can actively do something about to help lower our cholesterol.

Things that increase our cholesterol that we have the ability to change include:

• Smoking
• Lack of exercise
• Eating an unhealthy diet, especially one that is high in saturated fat
• Being overweight, especially with too much fat around our waist
• Having poorly controlled type 2 diabetes
• Drinking too much alcohol

Can you inherit high cholesterol?

At least one in 250 – 500 people in Ireland have an inherited condition called familial hypercholesterolemia (FH), which results in exceptionally high cholesterol levels [8]. However, over 90% of people with FH have not been properly diagnosed. This means that of 5 million people in Ireland, approximately 10,000 people, at least, could have FH. [8] FH is caused by an abnormal gene that prevents LDL cholesterol from being removed from the blood as effectively as it should be. This means anyone with FH can have unusually high total blood cholesterol levels, usually between 7.5 and 12mmol/l but sometimes much higher. This means they are at risk of getting diseases of the heart and circulation at an early age, if the condition isn’t treated.

Because it’s a genetic condition, FH passes from a parent to a child. As there are often few signs or symptoms of the disease, all close relatives, including children, should get their blood cholesterol levels measured if one person in the family is diagnosed with this condition. Whilst eating a healthy diet is important, it’s unlikely to lower cholesterol alone in people with FH – most people will also need to take cholesterol-lowering medication. Your GP will be able to advise and refer you to a specialist clinic.

For more information, visit the Irish Heart Foundation website.

How can I reduce my cholesterol?

If you’re diagnosed with high cholesterol, instead of thinking of it as a death sentence, look at it as a helpful indicator of your heart health – and, most importantly, as something you can change.

Your GP may recommend medication to bring cholesterol down to healthier levels, if your risk of developing CVD in the next ten years is high. Statins are amongst the most popular medications used – they work by blocking the production of cholesterol in the liver, which helps to lower ‘bad’ cholesterol – but your GP will discuss and prescribe the right one to suit you.

Always enjoy a healthy, balanced and varied diet alongside taking your statin, and why not introduce cholesterol lowering to your daily diet, as they can add to the effects of your statin medication.

Always take medication that’s prescribed for you and never stop taking it without talking to your doctor first.

However, for many people, a few simple lifestyle changes are often the first – and only – line of treatment needed to lower cholesterol. Better still, many of these lifestyle changes can have many other benefits that help to keep our heart – and other parts of our body – healthy, too, including lowering high blood pressure and helping us lose weight.

Start with these to reduce cholesterol:

1. Give up smoking

Smoking has a triple impact on our cholesterol levels. Firstly, it makes ‘bad’ cholesterol more sticky so it’s easier to attach to the walls of our arteries, making them narrower. Secondly, it lowers ‘good’ cholesterol, the type we want more of as this carries cholesterol away from the arteries. And thirdly, some of the chemicals in cigarettes can damage the artery walls – bad news as cholesterol is more likely to be deposited in damaged parts of the arteries. Ask your GP or practice nurse for advice on giving up. Or visit the HSE website for advice on quitting.

Research suggests that smoking as little as one cigarette a day can increase the chances of heart problems. Men and women who smoked just one cigarette a day were 48% and 57% more likely, respectively, to suffer with coronary heart disease than non-smokers. The risk of having a stroke also increased in men and women who had one daily cigarette compared with non-smokers [9].

2. Get active

Exercising regularly can help to decrease ‘bad’ cholesterol and increase ‘good’ cholesterol. But it can also have other heart health benefits such as aiding weight loss, lowering blood pressure and reducing the risk of developing type 2 diabetes.

Adults should aim for at least 150 minutes of moderate intensity activity a week (that means getting out of breath and a little sweaty). It works out at just over 20 minutes a day. Moderately intense activities include brisk walking, cycling, dancing, low-impact aerobic workouts, hiking and mowing the lawn. Alternatively, you can do 75 minutes of high intensity activity each week, such as jogging, high-impact aerobics or skipping. If you’re new to activity, speak to your GP or practice nurse first for advice on getting started and exercising safely. Learn more about the many benefits of exercise.

3. Overhaul your diet

Changing your eating habits is one of the biggest – and best – steps you can take to help lower ‘bad’ cholesterol and increase ‘good’ cholesterol. It can also help you lose weight if you need to and reduce raised blood pressure. The key is to enjoy a healthy, balanced diet that includes plenty of plant-based foods such as fruit, veg, wholegrains, beans, lentils, nuts and seeds, contains two weekly portions of fish, limits saturated fat, sugar and salt, and doesn’t exceed healthy limits for alcohol. There’s also good evidence that adding cholesterol lowering foods can go a long way towards managing cholesterol, when they’re eaten as part of a healthy diet and lifestyle.

Read more cholesterol tips how to reduce cholesterol.

*Plant stanol ester has been shown to lower cholesterol. High cholesterol is a risk factor in the development of coronary heart disease. A daily intake of 1.5–2.4 g of plant stanols can help lower cholesterol by 7-10% in just 2-3 weeks, as part of healthy diet and lifestyle [10].