Understanding Cholesterol: A Guide to Heart Health

When understanding cholesterol, it is a well-established fact that it is one of the culprits which leads to heart disease. Awareness of this risk factor is widespread, but there still exists confusion about what is normal cholesterol level and the various types of cholesterol. To add to the confusion, some cholesterol is called good, while some is called bad.

Cholesterol is a soft, white, fat-like substance made in the liver and found in your body's cells. It plays an important role in the production of cell membranes and hormones, as well as in the digestion of certain foods. Cholesterol is also found in foods of animal origin, such as meats and milk. It is not found in plant products.

While manufacturers of vegetable oils sometimes advertise that their oil does not contain cholesterol, recent scientific consensus indicates that dietary cholesterol itself is not the primary driver of cardiovascular risk. Instead, the main dietary culprit for elevated cholesterol is saturated fat.

To travel to your cells, cholesterol must attach to a protein. The combination of cholesterol and protein is known as a lipoprotein (lipo or lipid means fat). There are several different lipoproteins, but two are most important to remember: LDL (low-density lipoprotein) and HDL (high-density lipoprotein). These, along with your total cholesterol and triglycerides, make up your lipid profile.

What is LDL?

Having a high LDL cholesterol level increases your risk for coronary heart disease. LDL is called "bad" cholesterol because it causes atherosclerotic plaque to build up inside your coronary arteries and block the flow of blood to your heart muscle. Blockages can cause chest pain or angina, and plaques that rupture can cause blood clots to form and trigger heart attacks.

What is HDL?

Having a high HDL cholesterol level reduces your risk for coronary heart disease. HDL is called "good" cholesterol because it helps to remove LDL cholesterol from the walls of your coronary arteries. This is important because it means coronary heart disease can be reversed.

What are Triglycerides?

Triglycerides are fatty substances found in the bloodstream. Most of the body's fat is stored in the form of triglycerides for later use as energy. High triglycerides are associated with the build-up of blockages inside the coronary arteries. People with high triglycerides, high LDL cholesterol, and low HDL cholesterol are at the greatest risk for coronary heart disease. Extremely high triglycerides can also cause inflammation of your pancreas, which is very dangerous.

Causes of High LDL Cholesterol

Of the various organs in your body, the liver plays the most important role in determining your LDL cholesterol level. As blood flows through the liver, special receptors on the surface of the liver cells remove some of the LDL cholesterol.

Genetic Factors 

• Number of LDL receptors you are born with.

• Activity level of your LDL receptors.

• Amount of cholesterol made by your liver.

• Elevated Lipoprotein(a): Also known as Lp(a), this is a highly heritable and independent risk factor for heart disease that should be screened in adults.

Lifestyle Factors

• Amount of saturated fat you eat: This is the primary dietary driver of elevated LDL and should ideally be limited to less than 6% of daily calories for optimal cardiovascular health.

Other Factors

• Certain diseases, such as thyroid problems, liver disease, diabetes, and kidney disease.

Cholesterol and Triglyceride Goals

It is more important to focus on the entire lipid profile than on your total cholesterol number. In some cases, looking at only the total cholesterol number is misleading. It is possible to have a normal total cholesterol level due to a high LDL cholesterol together with a low HDL cholesterol. But a high LDL and a low HDL are bad and put you at risk for coronary heart disease. It is also possible to have a high total cholesterol level due to a high HDL cholesterol, which is good if your LDL cholesterol is low.

The following are the updated values recommended to keep your risk for heart disease to a minimum:

• Total Cholesterol: < 200 mg/dl

• Triglycerides: < 150 mg/dl

• HDL Cholesterol: > 40 mg/dl

• LDL Cholesterol: Targets are now based on individualized risk assessments:

  • < 100 mg/dL: For individuals at borderline or intermediate risk.

  • < 70 mg/dL: For individuals at high risk.

  • < 55 mg/dL: For individuals at very high risk or with established clinical atherosclerotic cardiovascular disease (ASCVD).

Author: Dr. Aashish Contractor is India's pioneer in cardiac rehabilitation and the Founding Medical Director of the Mumbai Marathon. With over 25 years of experience, he has guided hundreds of heart patients to run safely.