Blood lipids: What do they reveal about our cardiovascular health?

Cholesterol is only part of the story. In this article, we explore how fats travel through the body, the role of lipoproteins, and why increasing attention is being paid not only to the amount of lipids in the blood but also to the particles that transport them.

What are lipids and why do we need them?

Fats, or lipids, are essential components of the human body. They provide energy reserves, contribute to the formation of cell membranes, help the body absorb fat-soluble vitamins (A, D, E and K), and are necessary for the synthesis of various hormones.

However, lipids do not dissolve well in water (as we know, oil and water do not mix!). Therefore, a specialised transport system is needed to carry them through the bloodstream. Most triglycerides and cholesterol in the blood are transported as part of lipoproteins.

What lipids and lipoproteins circulate in the blood?

We most commonly hear about total cholesterol, LDL and HDL cholesterol, as well as triglycerides. However, each of these measurements provides different information.

Cholesterol is a substance essential to the body. It contributes to the formation of cell membranes and the synthesis of steroid hormones. The body obtains cholesterol both from food and through its own production.

Triglycerides are the main form of fat in which the body stores energy. Their levels in the blood may increase after eating, particularly following meals rich in fat, although other metabolic factors also influence them.

Lipoproteins are transport particles that contain cholesterol and triglycerides, delivering them to tissues or helping transport them away from the bloodstream. They differ in size, composition, density and function. These differences are also important in the context of cardiovascular health.

Lipoproteins contain apolipoproteins on their surface, which stabilise the particle structure and carry the molecular signals required for lipid transport. They enable lipoproteins to interact with cell receptors and metabolic enzymes. The size and composition of a lipoprotein, as well as the types of apolipoproteins it contains, influence how it travels through the body and is metabolised.

Figure 1. Structure of a chylomicron, the largest type of lipoprotein. T indicates triglycerides, while C indicates cholesteryl esters. Image adapted from the original. Source: .

LDL and HDL: Is it really just a matter of good and bad cholesterol?
Low-density lipoproteins (LDL) are commonly referred to as “bad cholesterol”, while high-density lipoproteins (HDL) are known as “good cholesterol”. These terms simplify a complex process, but they do not fully reflect the nature of lipid metabolism.

Lipoprotein size and density are generally inversely related: the larger the particle, the lower its density.

LDL particles deliver cholesterol to the body's cells. When excessive amounts of LDL circulate in the bloodstream over a prolonged period, they can become retained in arterial walls, contributing to the narrowing of arteries and the formation of blood clots. Over time, this increases the risk of heart attacks and strokes. Excessive consumption of saturated fats can also increase LDL cholesterol levels.

HDL participates in transporting cholesterol from tissues back to the liver, where it can be metabolised or eliminated from the body in the form of bile acids, helping reduce cholesterol accumulation in the arteries. However, a high HDL cholesterol level alone does not guarantee protection against cardiovascular disease.

In addition to LDL and HDL, other classes of lipoproteins also play an important role in lipid transport and metabolism, including:

Very-low-density lipoproteins (VLDL) primarily transport triglycerides from the liver to tissues. As triglycerides are removed during metabolism, VLDL particles gradually become LDL particles.

Lipoprotein remnants are formed when some of the triglycerides are removed from triglyceride-rich lipoproteins. These particles can contain cholesterol and also contribute to the development of atherosclerosis.

Lipoprotein(a), or Lp(a), is a particle structurally similar to LDL, but with an additional protein attached to it called apolipoprotein(a). Lp(a) levels are largely determined by genetics, and elevated levels are associated with an increased risk of atherosclerotic cardiovascular disease. European guidelines highlight Lp(a) testing as an important tool for refining cardiovascular risk assessment.

This is why it is important to consider the overall picture rather than relying on a single number or the simplified distinction between “good” and “bad” cholesterol.

How do lipids travel through the body?

Figure 2. Lipid transport in the body.

After a meal, the transport of dietary fats to tissues begins in the intestines, primarily with the help of chylomicrons, the largest lipoprotein particles.

The liver produces and processes lipoproteins, including very-low-density lipoproteins (VLDL), which transport triglycerides to tissues.

In the bloodstream, lipoproteins facilitate the transport of fats and cholesterol. LDL particles deliver cholesterol to tissues, while HDL participates in transporting cholesterol back to the liver.

This system is essential for normal bodily functions. Problems arise when the concentration of certain lipoproteins becomes elevated or their metabolism is disrupted.

Why is total cholesterol not always enough?
A standard lipid panel typically measures total cholesterol, LDL cholesterol, HDL cholesterol and triglyceride concentrations. These are among the most important measurements used to assess cardiovascular risk.

However, it is important to understand that cholesterol concentration does not reveal all the information about the lipoprotein particles that transport it.

For example, two people may have similar LDL cholesterol concentrations but different numbers of lipoprotein particles. In such situations, measuring apolipoprotein B (ApoB) can provide additional information.

ApoB is a protein found on the surface of most atherogenic lipoprotein particles. Its concentration therefore helps estimate the total number of these particles circulating in the blood. ApoB testing may be particularly useful for people with elevated triglyceride levels, diabetes or previously diagnosed cardiovascular disease.

What influences blood lipid levels?
Lipid metabolism is influenced by a combination of factors, including:

• Genetics
• Diet
• Physical activity
• Body weight
• Age
• Hormonal changes
• Certain medical conditions, such as diabetes, thyroid disorders and kidney disease
• Medications

Some of these factors can be modified, for example, by improving dietary habits, exercising regularly and quitting smoking. However, a genetic predisposition to elevated levels of certain lipoproteins may persist even in people who maintain a healthy lifestyle.

Therefore, a healthy body weight or balanced diet does not automatically rule out an increased cardiovascular risk. Likewise, an isolated elevated measurement does not necessarily mean that a person will develop cardiovascular disease.

The most important thing is to assess cardiovascular risk in a timely manner and, when necessary, work with a healthcare professional to choose the most appropriate prevention or treatment strategy.

How can we learn more about our lipid metabolism?
Standard blood tests are an important first step in assessing cholesterol and triglyceride levels. However, in certain situations, more detailed information about the composition, quantity and distribution of lipoproteins can provide a better understanding of the body's lipid metabolism.

Doctors can use this additional information to refine cardiovascular risk assessment, particularly when standard measurements do not fully reflect the overall clinical picture.

At the same time, it is important to remember that no single test can fully predict future health outcomes. Laboratory results should always be interpreted in the context of a person's health status, family history and other risk factors.

Understanding lipids involves much more than simply reading a cholesterol number on a laboratory report. The better we understand the role of different lipoproteins in the body, the clearer it becomes why looking beyond standard measurements can sometimes provide valuable insights into cardiovascular health.

This information is intended for educational purposes only and does not replace medical consultation, diagnosis or individual treatment recommendations.

References:
American Heart Association. HDL (Good), LDL (Bad) Cholesterol and Triglycerides. https://www.heart.org/en/health-topics/cholesterol/hdl-good-ldl-bad-cholesterol-and-triglycerides [Accessed 27 October 2026.]
Borén, J., & Williams, K. J. (2016). The central role of arterial retention of cholesterol-rich apolipoprotein-B-containing lipoproteins in the pathogenesis of atherosclerosis: a triumph of simplicity. Current Opinion in Lipidology, 27(5), 473–483. https://doi.org/10.1097/MOL.0000000000000330
European Atherosclerosis Society. 2025 Focused Update of the 2019 ESC/EAS Guidelines for the management of dyslipidaemias. https://eas-society.org/publications/guidelines/2025-focused-update-of-the-2019-esc-eas-guidelines-for-the-management-of-dyslipidaemias/
Structure of a chylomicron. Source: Xvazquez (2008). Licensed under CC BY-SA 3.0, via Wikimedia Commons.
Mach, F. et al. (2019). 2019 ESC/EAS Guidelines for the management of dyslipidaemias: lipid modification to reduce cardiovascular risk. European Heart Journal. https://doi.org/10.1093/eurheartj/ehz455
National Lipid Association. (2024). Role of apolipoprotein B in the clinical management of cardiovascular risk in adults: An Expert Clinical Consensus. Journal of Clinical Lipidology. https://pmc.ncbi.nlm.nih.gov/articles/PMC11734832/