What is lipoprotein, and what does it mean for health?

You may have heard this term related to cholesterol, but what are these particles, and how are they related to cardiovascular risk?

WRITTEN BY

Nicola Bridges

REVIEWED BY

Neil Kathuria, MD

Updated: 07/09/2025|12 min read

When you get your cholesterol checked, you'll encounter acronyms like LDL and HDL (which stand for low- and high-density lipoprotein) and be told that one is bad and the other is good. Although that's an oversimplification, these two types of cholesterol indeed do very different things in your body. And yet, they're both the same type of particle: a lipoprotein. So, what are lipoproteins, and what are they doing in our bodies?

Lipoproteins are transporters. They move cholesterol and other lipids (fats) through the bloodstream. (The name means "fat-proteins," from the Greek roots "lipos" [fat] and "proteios" [protein]). Their role as a package is to shuttle lipids to wherever they're needed in the body and keep them from clumping together.

Measuring these containers is a way to measure our lipid levels, which have implications for several areas of our health and are driven partly by genetics and heavily by lifestyle factors, including diet and exercise.

Using these measurements to assess cardiovascular risk has been standard practice for decades, but current data demonstrates that these levels are more nuanced than simply counting high-density lipoprotein (HDL) and low-density lipoprotein (LDL). Research shows that cholesterol particle size and density are also significant risk factors, and this information isn't provided by a cholesterol panel alone. Checking other biomarkers (such as ApoB lipoproteins) can provide deeper insights about your lipoproteins and health risk.

In this guide, we'll explain what you need to know about lipoproteins, how they impact cardiovascular health, and what you can do to help keep your lipoproteins in an ideal range.

What is lipoprotein?

Lipoproteins are essential molecules that our body needs to transport and deliver lipids (such as cholesterol and triglycerides) throughout the body to support cellular structure, hormone production, and brain health.

Lipoprotein structure

Lipoproteins consist of a hydrophilic outer shell (it can mix with or dissolve in water) and a hydrophobic core (it can repel or fail to mix with water). This structure allows lipoproteins to transport fat molecules in our watery blood and move freely without clumping together.

Apolipoprotein B (ApoB)---the primary protein in all non-HDL lipoproteins: chylomicrons, VLDL, IDL, LDL and Lp(a)---provides structural support while also acting as a ligand, or molecule that binds to receptors on cell surfaces. By binding to receptors, ApoB directs lipoproteins to specific tissues in the body, effectively serving as a signaling molecule that triggers or influences cellular responses.

Classes of lipoproteins and their function

Each of the five main classes of lipoproteins has a distinct role and different composition of elements (triglycerides, phospholipids, free cholesterol, cholesterol esters, and apolipoproteins) that results in its density (grams per milliliter or g/mL).

• Chylomicrons transport triglycerides derived from food from the small intestine to tissues that need them. They're the largest and least dense lipoproteins. Chylomicrons are too large to enter the arterial wall and are not considered atherogenic, but remnant chylomicrons---what's left after their fat content is stripped out for use or storage, and are therefore smaller---are atherogenic.
• Very low-density lipoproteins (VLDL) carry triglycerides from the liver to tissues. As they lose triglycerides, VLDL becomes IDL.
• Intermediate-density lipoproteins (IDL, sometimes referred to as middle-density lipoproteins or MDL) are precursors to LDL and are formed as VLDL loses triglycerides. They contain both cholesterol and triglycerides.
• Low-density lipoproteins (LDL) deliver cholesterol to cells. In excess, LDL can penetrate the endothelium, the thin inner lining of the heart and blood vessels, and deposit cholesterol in arterial walls, causing plaque to build up (atherosclerosis) and risk clogging arteries. However, the size of the LDL particle also matters. Small, dense LDL particles are more likely to penetrate arterial walls and contribute to atherosclerosis than large, buoyant ones. An important variant of LDL is lipoprotein (a), structurally similar but with an extra protein attached. Lipoprotein (a) is an atherogenic cholesterol-carrying particle that looks like "regular" LDL but has an extra protein attached. It's mostly genetically determined and doesn't change much over time.
• High-density lipoproteins (HDL) remove cholesterol from cells and transport it back to the liver for excretion, a process known as reverse cholesterol transport. This clearance effect is why HDL is often considered beneficial. HDL is produced in the liver and intestines.

The classes of lipoproteins work together to ensure the efficient and effective transport of lipids throughout the body to provide essential building blocks and energy sources.

How does lipoprotein metabolism work?

Lipoprotein metabolism is a subset of lipid metabolism that focuses on the assembly, transport, and removal of lipids by the circulatory system. Both are crucial for maintaining lipid homeostasis---the body's ability to self-regulate lipid function and maintain the proper levels, regardless of external influences---and reducing the risk of cardiovascular disease.

The following functions play a role in lipoprotein metabolism:

• Enzymes, including LCAT (lecithin-cholesterol acyltransferase) and CETP (cholesteryl ester transfer protein), modify and remodel lipoproteins while in circulation to change their composition and function. LCAT transfers a fatty acid from lecithin to free cholesterol in HDL, creating a cholesterol ester, where it moves into the core of the HDL. This process, called esterification, is how the HDL molecule picks up more cholesterol for removal from the body. CETP transfers cholesterol esters from one lipoprotein to another. This helps control the ratio of HDL to LDL cholesterol.
• Through receptor-mediated uptake, cells use their receptors to recognize ApoB lipoproteins and take up the lipids needed for energy, building cell membranes, and signaling.

When lipoprotein metabolism functions properly, essential lipids are delivered where needed and removed when in excess. When it dysfunctions, it can contribute to cardiovascular disease and metabolic disorders, and affect almost every system in the body.

How do lipoproteins affect cardiovascular health?

A combination of genetic variants and lifestyle factors, including diet, exercise, and smoking shapes lipoprotein levels. Abnormal levels of lipids in the bloodstream (dyslipidemia) and imbalances in lipoprotein metabolism can lead to chronic health issues, including metabolic syndrome, neurodegenerative disorders, and cardiovascular disease.

In particular, LDL cholesterol can contribute to the buildup of plaque in the artery walls (i.e., atherosclerosis), which reduces blood flow and increases the risk of heart attack or stroke. When the artery lining is inflamed or damaged, LDL can embed in it and become oxidized, setting off a series of reactions that result in plaque growth.

Atherosclerosis in different arteries puts you at risk of other cardiovascular conditions:

• Coronary artery disease: atherosclerosis in the coronary arteries
• Stroke: atherosclerosis in the arteries supplying the brain
• Peripheral artery disease (PAD): atherosclerosis in the arteries supplying the hands and feet
• Calcific aortic valve disease: lipid-contributed buildup of calcium in the aortic valve

But there's more to this story. HDL, ApoB, Lp(a), and other subclassifications of lipoproteins also impact cardiovascular health.

HDL typically has a positive influence. It not only reduces cholesterol buildup in blood vessels, but it also has anti-inflammatory, antioxidant, and anti-blood clotting effects. These properties are likely why HDL also helps protect the endothelium. Endothelial function influences blood clotting, vascular tone (responsible for determining blood vessel diameter and therefore rate of blood flow), blood-tissue barrier maintenance (essential for sealing major organs from harmful substances), and immune function. However, while HDL is considered "good" cholesterol, excessively high levels of HDL (greater than or equal to 80 mg/dL) may have adverse consequences. Researchers are still learning what specifically HDL does in the body.

Conversely, ApoB is the main protein in atherogenic lipoproteins---LDL, IDL, VLDL, and lipoprotein(a)---which promote plaque buildup in the arteries. Each lipoprotein molecule contains one ApoB protein molecule, so an ApoB blood test provides a more accurate count of the number of potentially harmful (atherogenic) lipid particles in the blood. This makes it a better predictor of cardiovascular risk than LDL cholesterol level alone, which only reveals the amount of low-density lipoprotein in your blood.

Lastly, lipoprotein(a), which is largely genetically determined, is an independent risk factor for atherosclerotic cardiovascular disease. Elevated levels of Lp(a) can significantly increase the risk of heart attack, stroke, and other cardiovascular events, as it makes cholesterol more likely to form and accumulate arterial plaques on blood vessel walls. 

How to manage lipoprotein levels

Maintaining a healthy balance of lipoproteins is crucial for preventing cardiovascular issues; lifestyle choices can significantly impact this.

Be mindful of saturated fats

Saturated fats---found in high levels in foods like butter, many cheeses, and red meat---can contribute to increased LDL. However, recent research increasingly questions the long-held belief that these fats categorically increase cardiovascular disease by raising LDL cholesterol. Instead, findings suggest that saturated fat risk is highly individual, both genetically and in how it interacts with other health markers, including elevated ApoB, triglyceride levels, and small dense LDL particles.

For example, in a trial of 195 adults with moderate cardiovascular disease risk, increasing saturated fat intake by about 6 percent led to an increase in LDL of up to 45 percent in some people, but a decrease of up to 20 percent in others. Researchers say a combination of genetics, gut health, the source of saturated fat, and other factors may influence these changes.

There's no agreement on how much saturated fat is considered safe to consume. Some experts say you can include saturated fats in a balanced diet of nutrient-dense foods without worrying. However, the Dietary Guidelines recommend keeping saturated fat under 10 percent of total daily calories (22 grams per day on a 2,000-calorie-per-day diet), and the American Heart Association suggests no more than 6 percent of daily calories (13 grams). Take your risk factors and experience into account when figuring out your best intake with the help of your doctor.

Avoid tobacco and limit alcohol

Smoking has well-established negative effects on cardiovascular health. It lowers HDL, raises inflammation, promotes LDL oxidation, and accelerates plaque formation. Even low levels of smoking exposure can negatively impact lipoprotein profiles. The good news: Quitting smoking can lead to rapid improvements in HDL and endothelial function, with some changes measurable within weeks.

When it comes to alcohol, moderation is key. Excessive alcohol intake---roughly defined as more than four drinks per day---can increase blood pressure, raise triglyceride levels, and elevate the risk of heart rhythm disorders and stroke. While some studies have associated moderate drinking with higher HDL levels, recent evidence suggests that any cardiovascular benefits may be offset by other health risks, including increased cancer risk. If you do drink, it's safest to do so in moderation---and there's little evidence to support starting alcohol consumption for health reasons.

Omit processed trans fats

The trans fats in fast foods and processed foods not only boost LDL but also lower HDL. Trans fats are also present in some unprocessed foods---mostly meat and dairy, including beef, lamb, and butterfat---but their cardiovascular effects are unclear. Overall, it's recommended to avoid processed foods and limit natural sources as much as possible.

Eat more soluble fiber

Soluble fiber dissolves in body fluids and water, creating a gel-like substance in the GI tract. In addition to helping feed good gut bacteria and lowering blood glucose, soluble fiber helps reduce cholesterol by binding to foods in the intestinal tract, preventing its absorption into the bloodstream, and improving its excretion.

Daily fiber intake recommendations range from 21 grams to 38 grams, depending on sex and age, and combine soluble and insoluble fiber. However, Levels advisors recommend aiming for about 50 grams of fiber per day. Sources of soluble fiber include:

• Oat bran
• Seeds
• Nuts
• Barley
• Beans
• Lentils
• Peas

Boost your omega-3 intake

Omega-3 fatty acids have multiple positive impacts: They can reduce the secretion of very-low-density lipoprotein (VLDL)---which carries triglycerides---by increasing degradation of ApoB and clearing chylomicron, and by lowering the levels of triglycerides needed to make VLDL. Omega-3s also help improve HDL function. Learn more about the metabolic health benefits of omega-3s and the best dietary sources in our guide.

Prioritize physical activity

Regular physical activity (especially aerobic) has been shown to increase HDL, reduce triglycerides, and improve insulin sensitivity. Insulin helps regulate lipid metabolism, specifically lipolysis, the breakdown of fats to be used for energy.

Medication

If lifestyle changes don't help improve your lipoprotein levels, your physician may prescribe medication such as a statin, bile acid sequestrant, or PCSK9 inhibitor. Here's how they work:

• Statins inhibit cholesterol synthesis in the liver.
• Bile acid sequestrants bind to bile acids in the intestine and prevent them from being absorbed into the bloodstream; instead, they're excreted from the body. The body then needs more bile acid, which the liver makes by pulling cholesterol from the bloodstream.
• PCSK9 inhibitors increase the liver's ability to remove LDL from the blood.

Lipoprotein best practices

It's uncertain if lipid tests beyond the traditional cholesterol panel can provide insights into what actions to take to benefit your health. Still, you may want to discuss the following test options with your healthcare provider:

• ApoB test: This blood test looks for the amount of ApoB, which carries substances necessary for making plaque in your arteries, where they may start to build up.
• Direct LDL cholesterol: In most lipid panel tests, LDL cholesterol is estimated using an equation that involves other cholesterol measurements, whereas direct LDL specifically measures the level of LDL in your blood. This blood test is typically done for patients with known high triglyceride levels, a family history of high cholesterol or cardiovascular disease, or who have diabetes or obesity.
• Lipoprotein fractionation NMR: If you have an intermediate or high risk for cardiovascular disease, or to test improvement if you're already having lipid-lowering therapy. The lipoprotein fractionation NMR (nuclear magnetic resonance) spectroscopy blood test assesses the size and number of your lipoproteins.
• Lipoprotein fractionation, ion mobility: Also a blood test, LFIM discerns lipoprotein particle size, and it's considered the most accurate way to measure their size and concentration. It's regarded as the most accurate way to measure their size and concentration.

The bottom line

Lipoprotein profile management is crucial in preventing and managing cardiovascular disease and overall health. Regular checkups, a cholesterol blood test, and more advanced lipid panel testing can help monitor lipoprotein levels and identify potential risks early on. Whatever your test results, lifestyle changes can help you keep your levels in the healthy range or reduce harmful lipoprotein levels while boosting beneficial ones.

Test and improve your lipoprotein levels

Levels members can test their lipoprotein levels through Levels Labs, and then use the Levels app to help improve levels by logging meals and setting exercise goals. Click here to learn more about Levels.