What is cholesterol? All about HDL and LDL cholesterol

The word 'cholesterol' often immediately brings to mind associations with health risks and heart problems. Perhaps you also have a negative association with it. But is cholesterol good, bad, dangerous, helpful, or a bit of everything? When should you be concerned about high cholesterol? 

What is cholesterol?

Cholesterol is a fat-like substance that your body produces itself and is present in every cell of your body. Although it is often seen as a culprit, cholesterol is indispensable for your body. For example, you need it for: 

• The production of hormones: it is a building block for hormones such as oestrogen, testosterone, and cortisol. These hormones are important for your metabolism and reproduction. 
• The construction of your cell membranes: cholesterol provides strength and flexibility in your cells and ensures that your cells function properly.
• The production of bile acids: bile acids are important for digesting and absorbing fats from your diet. 
• The production of vitamin D: you also need cholesterol for the production of vitamin D. Vitamin D is important for strong bones and a well-functioning immune system. Want to know more? Read all about vitamin D here.

So cholesterol is actually more your friend than your enemy, unless the balance gets disturbed. This happens, for example, when you have too much oxidised LDL and thus run more risks of health problems.  

How is cholesterol produced?

Did you know that about 75% of your body's cholesterol is produced by your liver? Only 25% comes from food. This explains why a healthy diet is important, but not the only factor.

Your liver precisely regulates how much cholesterol your body needs. If you consume more cholesterol through food, your liver automatically produces less. But in some people, this mechanism can become disrupted, for example by: 

• Stress. Chronic stress can raise your cholesterol. More and more evidence shows that cholesterol levels are higher under stress. 
• An unhealthy lifestyle. Unhealthy eating, lack of exercise, and smoking cause many disruptions.
• Genetic predisposition. Hereditary factors can cause your body to naturally produce a lot of cholesterol.

If your body becomes unbalanced, your cholesterol can rise and your risk of cardiovascular disease may increase.

HDL versus LDL: good and bad cholesterol 

Cholesterol is often divided into 'good' and 'bad'. But what does that actually mean?

• HDL (High-Density Lipoprotein) cholesterol is known as 'good cholesterol'. It helps transport excess cholesterol from your blood vessels back to your liver, where it is broken down.
• LDL (Low-Density Lipoprotein) cholesterol is called 'bad cholesterol'. LDL carries cholesterol to your cells. If there is too much LDL in your blood, it can accumulate in your blood vessels. This does the opposite of HDL cholesterol. However, LDL cholesterol is not necessarily 'bad' on its own. It plays an important role in transporting cholesterol to cells where it is needed. The problem only arises when LDL is damaged by oxidation.

The difference between LDL and oxidised LDL 

Free radicals (harmful substances that can cause inflammation or damage) can damage your LDL cholesterol. This damaged LDL is called oxidised LDL. That's where things go wrong and more risks arise. 

This oxidation occurs more often with an unhealthy lifestyle, for example due to:  

• Smoking
• Unhealthy diet (think of sugar-rich and processed products)
• Chronic inflammation

Oxidised LDL is more quickly absorbed into the walls of your blood vessels, where it can form plaques (accumulations in your blood vessels). This increases the risk of atherosclerosis (artery hardening) and cardiovascular disease. 

The problem is not necessarily in LDL itself, but in how healthy your LDL is and how much it gets oxidised. To prevent LDL oxidation, you can focus on a diet rich in antioxidants: vegetables, fruits, nuts, and seeds. These substances help neutralise free radicals in your body, making them no longer harmful.

The role of inflammation 

High cholesterol is often directly linked to cardiovascular disease, but there is another important factor: inflammation.

When the inside of your blood vessels becomes damaged, your body sends (LDL) cholesterol to the site to repair the damage. Cholesterol acts like a plaster on the 'wound'. The vessel wall can be damaged by, for example, high blood pressure, inflammation, smoking, or stress.

If you have chronic inflammation, your body continues to make repairs, and plaques can form. These plaques can lead to narrowing of your blood vessels and pose many risks. So it's not just high cholesterol that's dangerous, but also the presence of (long-term) inflammation.

What can you do to reduce inflammation? 

• Limit inflammation as much as possible: avoid sitting still for too long, keep stress under control, and limit foods that can cause inflammation (such as sugars and trans fats).
• Keep your blood sugar levels stable. Fluctuations in your blood sugar increase inflammation. Therefore, choose carbohydrates with a low glycaemic index, such as sweet potatoes, quinoa, or whole grains.
• Ensure an anti-inflammatory diet rich in omega-3 fatty acids (oily fish), antioxidants (for example, from vegetables, fruits, and fresh herbs), and fibres.

What do your cholesterol levels mean? 

When you have your cholesterol measured, you usually get an overview of three values: 

1. Total cholesterol level: This is the sum of all types of cholesterol together
2. HDL cholesterol: Helps transport cholesterol to the liver, where it can then be broken down. 
3. LDL cholesterol: Transports cholesterol to the cells but can be problematic if it becomes oxidised.

Your cholesterol levels are measured in millimoles per litre of blood (mmol/L). For adults, the following guidelines currently apply:

• Total cholesterol: Less than 5 mmol/L is considered healthy 
• HDL cholesterol: More than 1 mmol/L for men and 1.2 mmol/L for women is desirable
• LDL cholesterol: Less than 3 mmol/L is ideal

When is your cholesterol too high? High cholesterol means that your LDL cholesterol level is higher than 3 mmol/L or that your total cholesterol is higher than 5 mmol/L. This increases the risk of problems such as heart attacks or strokes.

The influence of age and heredity on your cholesterol

Your cholesterol levels change with age. As you get older, your LDL cholesterol can increase, while HDL cholesterol can decrease. This is because your metabolism slows down and your body has more difficulty breaking down excess cholesterol.

In addition, heredity also plays a role. In familial hypercholesterolemia, your LDL cholesterol is naturally higher. 

If you are over 40 years old, have an unhealthy lifestyle, or have cardiovascular diseases in the family, it is wise to regularly check your cholesterol. Your GP can easily measure your cholesterol through a blood test. 

How to keep your cholesterol healthy? 

The good news is that you can influence your cholesterol levels yourself. Here are a few smart tips:

Eat plenty of antioxidants and fibres 

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