Low-Density Lipoprotein (LDL) is a particle that carries cholesterol and other fats through the bloodstream. Because fats cannot dissolve in blood, they must be packaged with proteins into particles called lipoproteins for transport. You can think of an LDL particle as a microscopic delivery truck for its cholesterol cargo. While your body requires cholesterol for basic operations, high levels of LDL particles can become a health concern.
The Function of LDL in the Body
The primary role of LDL is to transport cholesterol from the liver, where it is produced, to cells throughout the body. This delivery system is a necessary process for normal bodily function. Cells use the cholesterol supplied by LDL for several important jobs that maintain health.
One of the main uses for this cholesterol is building and maintaining cell membranes. Every cell is enclosed by a membrane that acts as a protective barrier, and cholesterol provides this membrane with necessary structure. The body also uses cholesterol as a building block for producing certain hormones, including estrogen, testosterone, and cortisol, and for the synthesis of vitamin D.
Why LDL is Known as “Bad” Cholesterol
The reputation of LDL as “bad” cholesterol stems from the consequences of having too much of it circulating in the blood. When LDL levels are excessive, these particles can undergo a chemical change known as oxidation. Oxidized LDL particles can penetrate the inner lining of arteries, a layer of cells called the endothelium, which sets off an inflammatory response.
The body’s immune system responds by dispatching white blood cells, specifically macrophages, to the site. These immune cells engulf the oxidized LDL particles, and in the process, transform into “foam cells” because of their fat-laden appearance.
These foam cells accumulate within the artery wall, forming what are initially called fatty streaks. Over time, these streaks can grow and harden into more complex structures called plaques in a process known as atherosclerosis. As plaque builds up, it narrows and stiffens the arteries, restricting blood flow. This can lead to cardiovascular events like heart attacks and strokes if the plaque ruptures and causes a blood clot.
Interpreting LDL Cholesterol Numbers
LDL cholesterol is measured through a blood test called a lipid panel, which reports the concentration of LDL in milligrams per deciliter (mg/dL). Healthcare providers use standardized categories to interpret these numbers and assess cardiovascular risk.
The following classifications are widely used for adults:
- An LDL level of less than 100 mg/dL is considered optimal.
- A reading between 100 and 129 mg/dL is categorized as near optimal or above optimal.
- Levels from 130 to 159 mg/dL are classified as borderline high.
- An LDL measurement between 160 and 189 mg/dL is considered high.
- Any level at or above 190 mg/dL is categorized as very high.
Falling into the borderline high, high, or very high categories indicates an increased risk of developing cardiovascular disease. These are general guidelines, and a doctor may recommend a lower target LDL for individuals with other health conditions, such as diabetes or a history of heart disease.
Key Factors That Raise LDL Cholesterol
Several factors can contribute to an increase in LDL cholesterol levels. Diet plays a significant role in influencing LDL concentrations. The consumption of saturated fats, found in red meat, butter, and full-fat dairy products, is a primary dietary driver of higher LDL. Trans fats, present in fried foods, baked goods, and processed snacks, also raise LDL levels.
Lifestyle choices are another major contributor. A sedentary lifestyle can lead to elevated LDL, and carrying excess body weight is strongly linked to unhealthy cholesterol profiles. Smoking is also a factor; it contributes to higher LDL and damages the endothelium, making it easier for LDL particles to invade artery walls.
Genetics can predispose some individuals to high cholesterol. A condition known as familial hypercholesterolemia is an inherited disorder that affects how the body recycles LDL cholesterol, resulting in very high LDL levels from a young age. This genetic influence explains why some people struggle with high cholesterol despite a healthy diet and active lifestyle.