Lipoproteins are protein molecules that transport fat in the body. They contain cholesterol and triglycerides. Examples include high-density lipoproteins (HDL), known as “good” cholesterol, and low-density lipoproteins (LDL) or “bad” cholesterol.

Lipoproteins carry triglycerides and cholesterol through the bloodstream for use throughout the body.

Cholesterol is a type of lipid. The liver makes all the cholesterol that the body needs to create bile acids, produce hormones, and so on. However, people also take in cholesterol through their diet.

High levels of cholesterol can build up in the arteries and increase the risk of cardiovascular disease. Doctors recommend limiting cholesterol levels overall, but HDL levels should be higher than LDL levels. HDL helps the body remove LDL and reduces the risk of health complications.

This article explains what lipoproteins are, how they relate to cholesterol, how cholesterol affects health, and how to get and maintain appropriate cholesterol levels.

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Yaja Mulcare

Lipoproteins are spherical molecules that have a core of cholesteryl esters (a form of cholesterol) and triglycerides. On the outside are types of lipid known as phospholipids, free cholesterol, and apolipoproteins or apo.

Experts categorize lipoproteins according to their size, biological role, and contents.

There are five main classes of lipoprotein particles. They have different functions and carry different substances:

  1. Chylomicrons: These are large, triglyceride-rich lipoproteins that intestinal cells produce from dietary fats.
  2. Very low-density lipoproteins (VLDL): The liver produces these triglyceride-rich particles, which are smaller than chylomicrons, though their size can vary.
  3. Intermediate density lipoproteins (IDL): These carry cholesterol and triglycerides.
  4. Low-density lipoproteins (LDL): These are the main carrier of cholesterol in the blood and they deliver to cholesterol-dependent tissues, such as the adrenal glands and the gonads.
  5. High-density lipoproteins (HDL): These play an essential role in reverse cholesterol transport — bringing cholesterol from other tissues to the liver. They also have antioxidant and anti-inflammatory properties and may help prevent atherosclerosis, or the buildup of fat in the arteries.

Each type is associated with different apolipoproteins. These are proteins that help them carry out specific functions.

Lipoproteins play essential roles in the body, specifically in:

  • the absorption and transport of lipids in the small intestine
  • transporting lipids from the liver to tissues
  • transferring lipids from tissues to the liver, also known as reverse cholesterol transport

During reverse cholesterol transport, the body removes excess cholesterol from the tissues and brings it back to the liver. Then, the gallbladder may remove it from the body, or the body redistributes it.

What is the link with triglycerides?

Lipoproteins also carry triglycerides, the most common type of fat in the body.

Triglycerides store energy from food, but high triglyceride levels can be harmful, especially if a person has high HDL and low LDL levels.

If this happens, fatty substances can build up in the artery walls, increasing the risk of a stroke or heart attack.

An appropriate balance of lipoproteins and cholesterol is essential for health.

High levels of LDL and VLDL cholesterol are linked with the development of atherosclerosis. In atherosclerosis, plaque builds up in the arteries, increasing the risk of heart attacks, stroke, and heart disease.

Some types of LDL are also more dangerous than others. Small, dense LDL particles are more likely to cause atherosclerosis than larger LDL particles.

This is because small, dense LDL particles circulate for longer and find it easier to enter and adhere to arteries. They are also more susceptible to oxidation, which happens when LDL interacts with unstable molecules called free radicals. High levels of free radicals can lead to damage and inflammation in the body.

HDL, meanwhile, helps remove excess cholesterol from the blood and protect against atherosclerosis.

Various dietary and lifestyle modifications can impact lipoprotein levels and reduce the risk of disease.

If blood tests show that lipid levels are not within appropriate limits, a doctor will likely discuss the options for managing them.

Current recommendations for optimal blood lipid levels for adults aged 20 years and over are as follows:

  • triglycerides: under 150 milligrams per deciliter (mg/dl)
  • LDL cholesterol: under 100 mg/dl
  • HDL cholesterol: at least 40 mg/dl for males and 50 mg/dl for females
  • total cholesterol: 125–200 mg/dl
  • non-HDL: less than 130 mg/dl

Below are some evidence-based ways to reach and maintain these optimal levels.

  • Eating more fiber: A high-fiber diet can reduce LDL cholesterol and triglyceride levels by 5–10%. Examples include beans, fruits, nuts, seeds, and whole grains.
  • Reducing excess body fat: This can improve HDL levels, decrease LDL and triglyceride levels, and help cut heart disease risk.
  • Increasing physical activity: Exercise can help lower blood lipid levels, boost HDL levels, and may reduce the concentration of small, dense LDL particles.
  • Limiting added sugar and processed foods: Studies have linked these to unhealthy lipoprotein levels and high triglyceride levels.
  • Cutting out processed meats: Studies have associated these with unhealthy blood lipid levels.
  • Choosing healthy fats: Fats from avocados, olive oil, nuts, and seeds may help improve blood lipid levels and decrease heart disease risk.
  • Taking an omega-3 supplement: Studies suggest that these supplements can reduce LDL and triglyceride levels and increase HDL levels.

Other strategies that may help include:

A doctor can help someone with high blood lipid levels or low HDL cholesterol levels to make a treatment plan that suits their specific needs. This may involve medications as well as lifestyle measures.

Anyone considering using a new supplement should also speak with a healthcare professional to ensure the supplement is safe to use.

How do statins help lower cholesterol?

Lipoproteins are molecules that carry fats around the body. They are essential for overall health, but it is important to maintain healthy levels.

People with high cholesterol or triglyceride levels, or those who need to boost their HDL levels, may benefit from lifestyle changes, such as exercising more, quitting smoking, or eating more whole foods. If these do not help, a doctor may recommend medication.