Find out about cholesterol’s role in the body, why it’s so important for our health and how to get the right balance
Written by Carole Beck on January 27, 2019
Reviewed by Dr Rob Hicks on January 29, 2019
Cholesterol has a reputation as something of a bad guy because high levels are linked to an increased risk of heart disease. But cholesterol is also essential for good health.
What is cholesterol?
Cholesterol is a type of fat found in every cell of your body. It’s a vital building block of the following:1
- cell membranes
- vitamin D
- hormones, like testosterone and oestrogen
- bile acid for digestion
Cholesterol is broken down in the small intestine and mixed with protein to form lipoproteins so that it can travel around the bloodstream, including:2
- low density lipoprotein (LDL) – this is thought of as ‘bad cholesterol’
- high density lipoprotein (HDL) – this is considered the healthier form
Why is LDL the ‘bad cholesterol’?
Both HDL and LDL have important jobs:3
- LDL transports cholesterol to the cells
- HDL carries cholesterol away from the cells to the liver to be broken down or removed by the body
However, if LDL brings more cholesterol to the cell than it needs, LDL particles are laid down on the inside of artery walls, forming fatty deposits.
This builds up as plaque, narrowing the arteries – a condition called atherosclerosis – and restricting blood flow, and so also oxygen and nutrients, to vital organs, such as the heart and brain. This leads to an increased risk of serious health conditions, including angina, heart attack and strokes.4
Where does cholesterol come from?
Remember, some cholesterol is still really important for our health – in fact, about 80% of our body’s cholesterol is made by your liver and intestines and only about 20% comes from our food.5 This includes:6
- egg yolks
However, the cholesterol in your diet isn’t really the issue – it has very little effect on your total cholesterol levels.
Instead, the problem is that consuming too much saturated fat and trans fat prevents the liver from processing cholesterol so well – so, in other words, eating a diet rich in these fats can excessively raise levels of cholesterol in your blood.
Saturated fats are found in foods like cream, butter, ghee and fatty cuts of meat, while trans fats are in fried foods, margarines and cakes.7
What is high cholesterol?
This is when doctors consider your total blood cholesterol or your LDL levels to be excessively high for your sex, age and weight. Blood cholesterol is measured in millimoles per litre of blood (mmol/L), and, according to the NHS, ideal levels should, generally, be:8
- total cholesterol – 5mmol/L or less for healthy adults, and 4mmol/L or less for high risk adults
- LDL – 3mmol/L or less for healthy adults, and 2mmol/L or less for high risk
- HDL – above 1mmol/L
What causes high cholesterol levels?
High cholesterol isn’t only about the saturated and trans fats in our diets. The following also raise your risk of having high cholesterol levels:9,10
- lack of exercise – it can raise your level of LDL cholesterol in particular
- being overweight or obese – it increases your risk of having high LDL cholesterol, and low HDL
- regularly drinking a lot of alcohol – it increases cholesterol levels and can lead to low HDL
- smoking – a chemical in cigarettes (acrolein) blocks HDL from transporting
- cholesterol away from cells to the liver
For about one in 250 people, a genetic link is the cause – a condition called familial hypercholesterolaemia. This means their cholesterol levels are higher from birth.11
What are the symptoms of high cholesterol?
Unfortunately, just as with high blood pressure, there are usually no symptoms of high cholesterol until you experience a medical emergency, like a stroke or heart attack.12
How to lower cholesterol levels
Medication can help, but it’s also important to make healthy lifestyle changes:
- lose weight if appropriate
- exercise regularly – the NHS recommends 150 minutes of moderate-intensity exercise a week to lower cholesterol13
- don’t smoke
- switch from saturated to unsaturated fats – oily fish, nuts, olive oil, seeds and avocado are sources of unsaturated fats. They can help lower LDL cholesterol and raise HDL cholesterol14
- get enough omega-3 – a 2017 study in Nutrients reported omega-3, found in oily fish and fish oil supplements, may help reduce cholesterol levels15
How to check your cholesterol levels
Ask your GP about having a test. Many pharmacies also offer the service and there are home-testing kits. Once you’re over 40, get your cholesterol levels checked every five years, or when medically advised.16
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies
1. Harvard Medical School. How it’s made: Cholesterol production in your body
2. MedlinePlus. LDL: The “Bad” Cholesterol
3. NHS. Overview: High cholesterol
4. As above
5. As Source 1
6. NHS. Lower your cholesterol
7. As above
8. As Source 3
9. NHS. Causes: High cholesterol
10. Nakanishi N, et al. Influence of alcohol intake on risk for increased low-density lipoprotein cholesterol in middle-aged Japanese men
11. British Heart Foundation. Focus on: Familial hypercholesterolaemia
12. Mayo Clinic. High cholesterol
13. NHS. Prevention: High cholesterol
14. As above
15. Pizzini A, et al. The Role of Omega-3 Fatty Acids in Reverse Cholesterol Transport: A Review
16. BBC Two. Should I check my cholesterol levels at home?