What is HDL cholesterol?
HDL cholesterol is often known as ‘good cholesterol’ because it helps to protect your heart and blood vessels from disease. It’s essential for good health, but it can sometimes be too high or too low, which can lead to problems with your heart health.
HDL stands for high density lipoprotein
Lipoproteins are little parcels of lipids (fats) and proteins, which transport fats around the body in the blood.
HDL cholesterol contains a lot of protein and relatively little fat. This means it’s very dense, which is why it’s called ‘high density’ lipoprotein.
HDL cholesterol is one of the five main types of lipoprotein. It carries about a quarter of the cholesterol in your blood. Most of the rest is carried in LDL (low density lipoprotein) cholesterol, sometimes called ‘bad cholesterol’ as it can lead to heart disease.
What are the main roles of HDL cholesterol?
HDL cholesterol has a protective role against diseases of the heart and blood vessels such as heart attacks and strokes. The cholesterol itself is a fat, so it’s not the cholesterol that is protective, but the HDL lipoprotein as a whole.
HDL has three main effects
- It removes excess cholesterol (fat) from the blood vessels and other tissues and returns it to the liver to be recycled or removed from the body.
- It has an anti-inflammatory effect, which helps protect the artery walls against LDL cholesterol (bad cholesterol).
- It has an anti-oxidant effect, which helps protect cells and important chemicals in the blood and tissues from being broken down.
Healthy HDL cholesterol levels are different for men and women. Young boys and girls have similar HDL levels, but in boys, HDL levels fall after puberty and remain lower throughout their lives.
- For women, HDL levels above 1.2mmol/L are thought to be healthy.
- For men, HDL levels above 1.1mmol/L are thought to be healthy.
HEART UK’s specialists believe that HDL is at its most protective at around 1.3-1.4mmol/L, and higher levels might not offer any extra protection.
Note that if you have high LDL cholesterol (bad cholesterol) and your doctor is considering treatment to lower it, high HDL levels are not a reason to avoid treatment.
How high is too high?
In the past, studies showed that lower HDL levels raise the risk of diseases of the blood vessels, while high HDL levels were protective. They suggested that the lower the HDL, the higher the risk of serious events such as heart attack and stroke, and the higher the HDL, the lower the risk. This would mean that raising HDL would lower the risk of illness.
More recent research suggests that HDL levels above 1.4mmol/L may not offer extra protection. In some cases, very high HDL could even raise the risk of serious problems such as a heart attack or stroke.
Some studies also suggest that for people with high LDL cholesterol which is now well-controlled, raising your HDL with medicines does not lower the risk of serious problems such as heart attacks.