Low HDL cholesterol

HDL cholesterol is a type of cholesterol that is essential for good heart health, and it can sometimes fall too low.

Why is HDL cholesterol important? 

What causes low HDL cholesterol?

Lower levels of HDL cholesterol can have an underlying cause such as a health problem or certain medications. If you have low HDL cholesterol, your doctor can try to find out the cause so that they can treat it and bring your HDL up to a healthy level. Below are some of the possible causes.

Smoking

Smoking can lower your HDL levels because a chemical in cigarette smoke called acrolein appears to change the way HDL works in the body. It does this by changing the structure of a protein called Apolipoprotein A1, which forms part of HDL cholesterol.

This might speed up the process of atherosclerosis (where fat clogs up the arteries) because HDL is less able to remove cholesterol from the artery walls.

If you stop smoking, your HDL levels can rise by up to 10% as long as you don’t gain weight, which can sometimes happen when people stop smoking.

Insulin resistance

If you have too much fat stored in your body, particularly around your waistline, the hormone insulin is less able to control your blood sugar. This is known as insulin resistance.

Insulin resistance can lead to type 2 diabetes and it’s one of the problems that makes up the metabolic syndrome, which raises the risk of heart attacks and strokes.    

Insulin resistance also leads to characteristic changes in the pattern of fats often referred to as ‘dyslipidaemia’. Typically, this means:

  • high triglycerides
  • low HDL cholesterol
  • normal or slightly raised LDL cholesterol. The LDL cholesterol also tend to be smaller and more harmful to the arteries.

Losing weight can help raise your HDL cholesterol. 

Genetic conditions

Rarely, very low HDL cholesterol can be caused by your genes.

  • Tangier disease. This is a very rare condition which causes no or very low levels of HDL cholesterol. LDL cholesterol levels are also usually low. A fault in a gene affects the transport of cholesterol from your cells to your HDL lipoproteins.
  • ApoA1 deficiency. ApoA1 deficiency is a rare disorder which causes no or very low levels of a protein called Apolipoprotein A1 (Apo A1) which is an important part of HDL.
  • Familial combined hyperlipidaemia (FCH). FCH is a fairly common condition believed to affect around 1 in every 100 people in the UK. It is similar to diabetes and insulin resistance in that it usually causes high triglycerides and low HDL cholesterol, and much higher LDL cholesterol. This pattern of blood fats is also influenced by diet and lifestyle. 

Medicines

Certain medications can sometimes lower HDL levels, including:

  • beta blockers
  • thiazide diuretics
  • androgens
  • progestogens
  • anabolic steroids. 

If you are taking any of these medications, don’t stop taking them without speaking to your health professional. It’s likely that any possible risks caused by low HDL cholesterol will be outweighed by the benefits of the medications.

Raising your HDL cholesterol levels

Identifying the causes of low HDL and acting on them where possible should help to raise or maintain your HDL cholesterol levels. 

There are also other things you can do.

Eat a healthy diet

We have lots of information about eating a healthy diet. In particular, try to eat only small amounts of fats.

Be more active

Regular aerobic exercise which raises your heart rate and gets you out of breath can raise your HDL cholesterol by about 5% within two months, improve your LDL levels and lower your triglycerides.

How long you exercise for is more important than the intensity you exercise at, according to recent research, although any length of time or intensity will have benefits.

Be a healthy weight 

Losing weight and inches around your waistline if you are overweight or carry your weight around your middle can help to raise your HDL cholesterol. Recent research shows that for every 1kg of weight loss, HDL rises by 0.01mmol/L. Even modest weight loss of 5-10% of your body weight appears to improve levels of blood fats.

Medicines to raise HDL cholesterol levels

Most medications only have a limited effect on HDL cholesterol levels.

  • Statins reduce LDL cholesterol, but they only have a small effect on HDL cholesterol.
  • Medicines called fibrates lower triglycerides but they only have a small effect on HDL cholesterol.
  • Other medications like Ezetimibe and PCSK9 monoclonal antibodies, may raise HDL cholesterol.

At the moment there is a lack of understanding among the experts about how the methods for raising HDL cholesterol could affect the HDL’s ability to remove fat from the blood vessel walls.