What is High-Density Lipoprotein (HDL) Cholesterol?
Key Takeaways
Cholesterol is needed throughout the body for building cell membranes as well as synthesizing substances like hormones.
High levels of cholesterol in the blood can increase heart disease risk by depositing into the walls of arteries, making them narrower and stiffer.
Lipoproteins function to transport fatty substances like cholesterol in the bloodstream.
High-density lipoproteins, or HDL, act to scavenge excess cholesterol from the bloodstream and return it to the liver to be processed and eliminated.
By preventing excess cholesterol from building up in the bloodstream, HDL reduces the risk of a heart attack or stroke.
Low HDL levels are associated with an increased risk, although very high HDL levels may also increase the risk.
In people with low levels, lifestyle changes, including increased exercise, replacing saturated and trans fats with unsaturated fats, and quitting smoking are helpful for increasing HDL.
Medications or supplements may be used in some people if lifestyle changes are not effective enough.
What is HDL?
Cholesterol is a very important substance in the human body. It’s used for building the membrane that surrounds every cell, as well as to build hormones and other substances.
Although cholesterol is necessary for health, too much cholesterol can potentially cause damage to the body. Excessive cholesterol can deposit into the walls of arteries, causing them to become stiffer and narrower. This can lead to symptoms like difficulty exercising, and it also increases the risk of a serious event like a heart attack or stroke.
Because cholesterol is a fatty substance, it doesn’t dissolve well in blood, which is mostly made up of water. The body needs a way to transport cholesterol through the bloodstream in order to get it to your cells. That’s what lipoproteins are for. A lipoprotein is a “shell” made up of proteins and phospholipids, which surrounds fatty substances like cholesterol and triglycerides.
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There are a few different types of lipoproteins, which have different functions in the body and also impact your heart disease risk in different ways. Low-density lipoproteins (LDL) increase your risk, while high-density lipoproteins (HDL) generally decrease your risk.
Why is HDL protective against heart disease? Are higher HDL levels always better, or is there such a thing as too high? If your HDL levels aren’t optimal, what can you do to address this?
Why is HDL Called “Good Cholesterol”?
The function of HDL is to scavenge excess cholesterol from the bloodstream and carry it back to the liver, where it can be processed and eliminated. This is known as “reverse cholesterol transport.”
Cholesterol causes damage by depositing into artery walls. HDL acts to remove cholesterol from the bloodstream, and so it prevents excess cholesterol from building up in the bloodstream and entering into the walls of the arteries. This is how HDL reduces the risk of heart disease.
Because it’s associated with a reduced risk for heart attacks and strokes, HDL is sometimes called “good cholesterol.” Studies have generally shown that higher HDL levels are associated with a lower risk for heart disease. Recent research has added some nuance to this view, as we’ll discuss later in this article—very high HDL levels might actually increase risk. Still, those with low HDL levels have an increased risk of a heart attack or stroke, compared to those with higher levels.
By contrast, the role of LDL is to carry cholesterol out to the tissues so that cells can use it. When LDL levels are high, then excess cholesterol builds up in the bloodstream. It tends to enter into the walls of the arteries, which increases the risk of a heart attack or stroke. This is why LDL is sometimes called “bad cholesterol.”
Factors Influencing HDL Levels
There are a number of different factors that can influence your HDL levels, including:
Genetics. If you have multiple family members with low HDL levels, your levels are more likely to be low.
Body weight. Those with a body weight that falls into the category of overweight or obesity are more likely to have low HDL levels.
Smoking. Cigarette smoke affects your body’s processing of cholesterol, and is associated with lower HDL levels.
Diet. People who eat more saturated fat, trans fats, and processed sugar generally have lower HDL levels.
Exercise. Research has consistently associated physical activity with HDL levels.
Certain medications. Some pharmaceuticals, including certain hormones as well as blood pressure medications, can reduce HDL levels.
Testing and Understanding HDL Levels
If your HDL levels are low, then you’re at an increased risk for having a heart attack. However, low HDL levels don’t produce any obvious symptoms. The only way to know your HDL level is to have a blood test. This must be ordered by a physician, who will also interpret the test results in context and suggest a plan to reduce your risk.
HDL is generally tested as part of a blood test known as a lipid panel. This test also examines your levels of LDL as well as triglycerides, which are a type of fat that the body uses for energy. To have this test, you will need to be in a fasting state, meaning that you haven’t eaten for the past 8 to 12 hours. This is usually accomplished by going in for your blood draw in the morning, before you eat breakfast.
According to the guidelines published by the Ministry of Health, these are the general guidelines for HDL:
Low: less than 1.0 mmol/L
Desirable: 1.0 to 1.5 mmol/L
High: 1.6 mmol/L or greater
While higher HDL is generally associated with a lower risk for a heart attack, more recent research has shown that it’s also possible for the HDL level to be too high. People with very high HDL levels (over 1.6 mmol/L) may be at an increased risk for experiencing a cardiovascular event like a heart attack or stroke. The goal is to keep your HDL in the desirable range – not too low, but not extremely high either.
It’s very important to interpret your HDL level in context. Research has found that the ratio between LDL and HDL cholesterol is a very important measurement of heart disease risk. This ratio should be 3.5 or less. The ratio is usually reported as part of a standard lipid panel report, but your doctor can also calculate it easily if the lab report does not do so.
Understanding More
How to Improve HDL Levels
If your HDL levels are too low, then increasing them can significantly reduce your risk of experiencing a heart attack or stroke. In general, lifestyle interventions are tried first. Effective ways to increase your HDL include:
Get more exercise. Physical activity has consistently been shown to increase HDL levels. The general recommendation is to get at least 150 minutes per week of moderate-intensity exercise – this means that you could talk while performing the activity, but it would be difficult to shout or sing. However, any amount of physical activity is better than none, so anything that you can do to exercise a bit more will be beneficial.
Eat a healthy diet. Saturated fat (found in red meat, butter, and dairy products) and trans fat (found in fried and packaged foods) reduce HDL levels as well as increasing LDL levels. Replacing these with unsaturated fat (found in olive oil, fish, avocados, and nuts) will help to raise your HDL levels and reduce your heart disease risk. Studies have also found that, beyond simply raising HDL levels, eating more unsaturated fats helps to improve HDL function, further decreasing your heart disease risk.
Quit smoking. Smoking greatly increases heart disease risk. Not only does it lower HDL and raise LDL, but it also impacts blood flow throughout the body. If you currently smoke even just a few cigarettes a day, quitting will greatly reduce your chances of experiencing a serious medical issue like a stroke or heart attack.
There are also medications that can be used to help increase HDL if these lifestyle changes don’t get it into the healthy range. These include statins, fibrates, and bile acid sequestrants. High doses of niacin, a B vitamin, may also be used in some people. While these medications may be effective, they can also have side effects. It’s important to talk to your doctor about the potential risks and benefits in your individual situation, so you and your doctor can work together to make the best decision for your long-term heart health.
Practical Tips
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HDL in Relation to Overall Cardiovascular Health
Your HDL level is just one important component of your overall cardiovascular health. To fully understand your heart health, you’ll need to consider your HDL in context. For example, comparing your HDL and LDL levels helps you to understand your heart attack risk.
Other measurements, like triglycerides (another type of fat that is carried in the blood and used for energy) are also important. Along with HDL and LDL, these three types of fats are measured as part of a standard lipid panel. The Ministry of Health recommends this test for everyone on a regular basis, starting at age 40.
In addition, there are other measurements that can be useful for understanding your cardiovascular health. For example, tests like lipoprotein (a) and apolipoprotein B can provide additional information about your risk for a serious event like a heart attack. C-reactive protein (CRP) is a measurement of chronic inflammation in the body, and is known to be correlated with heart disease risk as well as the risk of many other chronic health conditions. These tests are not generally included as part of standard screening bloodwork, but they can be valuable in clarifying your personal risk for heart disease, which helps you and your doctor to create a plan for reducing your risk and protecting your long-term heart health.
Establishing a baseline early allows you to track changes over time, so you can make informed decisions about your health.
NOVI Assessment Max provides a holistic cholesterol check that goes beyond the standard test. It offers a comprehensive evaluation of metabolic, hormonal and predictive markers (like apolipoprotein B), giving you a complete picture of your heart health, and empowering you to take control of it.
Unlike other tests that leave you to interpret results on your own, NOVI Assessment Max includes a pre- and post-assessment doctor consultation, to discuss what tests to take given your unique health goals and where your results are explained in detail. The doctor then prioritizes areas of improvement and provides personailzed actionable recommendations.
Plus, we offer health programs and expert coaches to support you in implementing these recommendations. Whether you need dietary changes, exercise plans, or medical interventions, our experts will guide you every step of the way.