Very-low-density lipoprotein is one of the complex particles known as lipoproteins that circulate in the bloodstream, transporting fats throughout the body. While most people are familiar with low-density lipoprotein (LDL) and high-density lipoprotein (HDL), VLDL plays an equally significant role in metabolic health. These particles are produced by the liver primarily to carry a specific type of fat called triglycerides, which are essential for energy storage and usage. High levels of VLDL are closely associated with an elevated risk of cardiovascular issues, making it an important marker for overall health.
VLDL’s Place Among Lipoproteins
VLDL is classified as a very low-density lipoprotein because its composition contains a high percentage of lipids relative to protein, resulting in a low density. It is structurally composed of various fats and proteins, with the core being predominantly triglycerides, which make up approximately 50% to 70% of the total lipid content.
By comparison, the more commonly discussed LDL particle contains a much higher proportion of cholesterol esters than triglycerides. VLDL, IDL (Intermediate-Density Lipoprotein), and LDL all share a single molecule of the structural protein apolipoprotein B-100 on their surface. This shared protein links them together in a metabolic cascade, illustrating their interconnected nature in fat transport.
The Primary Role of VLDL in the Body
The main function of VLDL is to act as the body’s delivery system for energy reserves. The liver synthesizes triglycerides from excess carbohydrates and fat, then packages them into VLDL particles for transport. VLDL then travels through the circulation, delivering these triglycerides to peripheral tissues like muscle and fat cells, where they are used for immediate energy or stored for later use.
As the VLDL particle circulates, an enzyme called lipoprotein lipase removes the triglyceride payload from its core. This removal causes the VLDL particle to shrink and become denser, transforming it into a VLDL remnant, also known as IDL. These IDL remnants are either taken up by the liver or undergo further processing by hepatic lipase to become the smaller, cholesterol-rich LDL particles.
How VLDL Levels Are Determined
VLDL is typically not measured directly in a standard lipid profile. Instead, the concentration of VLDL cholesterol is usually estimated from the measured triglyceride level. The most common method uses the Friedewald equation, which estimates VLDL cholesterol by dividing the total triglyceride concentration by five.
This calculation relies on the assumption that triglycerides are packaged into VLDL at a relatively consistent ratio of five-to-one with cholesterol. Because this estimation is based on a fixed ratio, a fasting blood sample is generally required for the test to ensure the triglycerides are primarily from VLDL, not recently consumed food. The estimation becomes inaccurate and is not used when triglyceride levels are very high, specifically above 400 mg/dL. A VLDL-cholesterol level above 30 mg/dL is generally considered elevated and indicates a high triglyceride count, which is associated with an increased risk of plaque buildup in the arteries and subsequent cardiovascular disease.
Lifestyle Adjustments to Reduce VLDL
The most effective way to lower VLDL cholesterol is by focusing on actions that reduce triglyceride production in the liver. A key strategy involves significantly limiting the intake of simple carbohydrates and refined sugars, particularly fructose, as the liver readily converts these into triglycerides. Replacing refined grains with high-fiber options like whole grains, beans, and vegetables can help reduce the amount of fat the liver manufactures.
Key Lifestyle Changes
- Regular aerobic exercise, such as a brisk walk or jog for at least 30 minutes most days of the week, can improve VLDL metabolism and lower triglyceride levels.
- Weight loss, even a modest reduction of 5% to 10% of body weight, can lead to a noticeable drop in circulating VLDL.
- Reducing or eliminating alcohol consumption is beneficial, as alcohol can significantly increase triglyceride production in the liver.
- Incorporating foods rich in omega-3 fatty acids, such as salmon or mackerel, can also help lower triglyceride levels.