Cholesterol is a waxy substance found in the blood that is needed by the body to build healthy cells. It is produced in the liver or absorbed through the diet from animal products.
Cholesterol is often considered harmful to health, but it is actually essential for health. It is one of the most important molecules in the body and performs many essential functions.
Cholesterol is a type of lipid. Lipids are fats and lipids that the body uses as a source of energy. Lipids include cholesterol, triglycerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL).
Dyslipidemia is a condition in which lipid levels are outside the normal range. This condition is directly linked to coronary artery disease.
Dyslipidemia is characterized by:
- Hypercholesterolemia – increased cholesterol only
- Hypertriglyceridemia – increased triglyceride only
- Hyperlipidemia – increased both cholesterol and triglycerides.
What is the important role of cholesterol?
Maintaining good cholesterol levels in the body is important for health. Cholesterol has many important roles in the body. Specifically:
- Cholesterol is an important structural component in a number of tissues, including the brain and nervous system. About 25% of the cholesterol in our body is located in the brain. In fact, high cholesterol levels are associated with better cognitive function in older adults.
- Cholesterol is a molecule that transports fat-soluble nutrients into cells for proper use.
- Cholesterol is an essential component of hormones, including progesterone, estrogen, testosterone, cortisol, and vitamin D.
- The body uses cholesterol to make bile acids, which help digest fats.
Types of Cholesterol
Cholesterol is transported in the blood by proteins attached to cholesterol. This combination of protein and cholesterol is called a lipoprotein. Lipoproteins are the mechanism for transporting cholesterol and fat. Lipoproteins have a phospholipid coat that acts as an emulsifier, helping fats and blood mix together.
There are different types of cholesterol based on what the lipoprotein carries: LDL, VLDL, and HDL.
1. LDL Cholesterol
Low-density lipoprotein (LDL) transports primarily cholesterol. The main role of LDL is to transport fat-soluble nutrients into cell membranes for use. LDL also helps transport saturated fats to cell membranes.
Although LDL is often considered “bad” cholesterol, its nature is more complex. There are different types of LDL particles depending on their size. LDL particle size is important in determining whether LDL may contribute to heart disease or have a protective effect on the heart.
LDL levels may be elevated in people with low thyroid activity because triiodothyronine (T3) increases the sensitivity of the LDL receptor on cell membranes. Lower T3 activity prevents LDL particles from attaching to cell membranes, reducing the amount of cholesterol and fat-soluble nutrients entering cells. As a result, the body adapts and increases total LDL cholesterol, similar to how insulin increases in response to insulin resistance.
Ideal range: 100-200
2. VLDL cholesterol
Very low-density lipoprotein (VLDL) primarily transports triglycerides to tissues. VLDL is similar to LDL, but LDL primarily transports cholesterol instead of triglycerides. Triglycerides make VLDL denser than LDL. Once VLDL is released, enzymes in the blood interact with triglycerides and convert lipoproteins from VLDL to LDL.
Ideal range: 5-30 mg/dl
3. HDL cholesterol
HDL, or high-density lipoprotein, has a high cholesterol-to-protein ratio (45-50% protein). Its main role is to “SCAN” LDL particles and transport them to the liver for recycling. Effectively removing LDL from the blood is important because LDL is very susceptible to oxidation. LDL that stays in the blood for a long time increases inflammation and the risk of heart disease.
Ideal range: 55-80
Levels above 100 may indicate chronic inflammation or active infection in the body.
4. Triglycerides
Triglycerides are a type of fat (lipid) found in the blood that provides energy for the body. It í necessary for health, but when high, they can contribute to heart disease and stroke. The optimal triglyceride level is 40-80.
Lipoproteins transport triglycerides to cell membranes, where they are broken down into fatty acids and converted into adenosine triphosphate (ATP). Cells use ATP to create energy. Triglyceride levels will be high in people with high insulin levels, insulin resistance, and fatty liver disease.
Ideal range: 40-80
Healthy Ratio
There are important ratios to consider when analyzing cholesterol levels. A balanced LDL/HDL and triglyceride/HDL ratio is essential for good health.
- LDL:HDL ratio: 3:1 or lower (2:1 is optimal)
- Triglyceride: HDL ratio: 2:1 or lower (1:1 is optimal). Higher triglycerides and lower HDL are often a sign of insulin resistance and high fasting insulin levels.
