High cholesterol: What is it, what causes it and what impact does it have?

What is Cholesterol | Where does cholesterol come from | Genetic Hypercholesterolaemia | Aging | liver diseases | Poor Diet | Lack of exercise | Obesity | Smoking | Diabetes | What high cholesterol can do to your body | heart and circulation | Brain & Nerves | Digestive System

Fun fact: Did you know that 47.7% of Malaysians are estimated to have high cholesterol?

To put this into context, every second person reading this article is likely to have high cholesterol.

Do you know enough about this common condition?

What is cholesterol?

Butter Melting – cholesterol under high temperature

Cholesterol is a waxy, fatlike substance that your liver produces. Your body uses cholesterol to build cell membranes, certain hormones, Vitamin D and bile acids that help you to digest fat.

In other words, we need cholesterol.

Cholesterol doesn’t dissolve in water, so it can’t travel through the body by itself. It needs to be transported by particles known as lipoproteins through the bloodstream.

Think of cholesterol as a person who can’t swim, and the bloomstream is the ocean that separates different organs. Lipoproteins are like a cruise ship that carries the cholesterol around from one organ to another.

Cholesterol lipoprotein analogy
Lipoproteins are like cruise ships carrying water-insoluble cholesterol around in the blood stream

Not the best analogy I know, but you get what I mean.

There are two major forms of lipoproteins:

Low-density lipoproteins (LDL), also known as “bad cholesterol,” help carry cholesterol from the liver to other parts of the body. LDL can build up in the arteries and lead to serious health problems, like heart attack or stroke.

High-density lipoproteins (HDL), often called “good cholesterol,” help return the cholesterol to the liver for elimination.

And high cholesterol happens when you have high LDL or low HDL or both.

What causes high cholesterol? Where does cholesterol come from?

In order to understand what causes high cholesterol, we first need to know where does cholesterol come from.

Sources of cholesterol

The cholesterol in your blood comes from two sources: the foods you eat and your liver. Your liver makes all the cholesterol your body needs. The remainder of the cholesterol in your body comes from foods derived from animals. For example, meat, poultry and full-fat dairy products all contain cholesterol, called dietary cholesterol.

Tip: Next time when you go grocery shopping, check out the nutritional labels of different foods. A nutritional label should tell you the amount of cholesterol a particular food contains

Related reading: Foods and cholesterol

Now, about 80% of cholesterol comes from your liver, which explains why some people are more likely to get high cholesterol regardless of what their diet’s like. Some foods that are high in saturated fats and trans fat can cause your liver to produce more cholesterol too.

Only about 20% of cholesterol comes from food. This means, if you found your cholesterol levels to be high, it’s very hard to get it down just by watching your diet. This is also why some medications that block absorption of cholesterol from diet don’t work as well as medications that prevent liver from producing too much cholesterol. (We will cover medications for high cholesterol in another article.)

What causes high cholesterol:

There are many explanations to your high cholesterol. Some of the common risk factors are:

  1. Genetic predisposition
  2. Age
  3. Presence of liver disease
  4. Poor diet
  5. Lack of exercise
  6. Obesity
  7. Smoking
  8. Diabetes

Familial Hypercholesterolaemia: It runs in the family

High cholesterol can be inherited from your parents, also known as familial hypercholesterolaemia.

With familial hypercholestrolaemia, there is a fault in one of the genes involved in removing cholesterol from the blood.

As a result, you are more likely to have high cholesterol, and you can pass on the gene to the next generation.

If you have familial hypercholesterolaemia, you need to worrk extra hard to prevent other risk factors – i.e watch your diet, exercise more often, avoid smoking etc.


Cholesterol levels generally go up when you age – as you age, your liver becomes less able to remove LDL cholesterol.

Related reading: 6 supplements recommended for seniors

Liver diseases

Liver is responsible for both producing and removing cholesterol in the body. If your liver is damaged (excessive alcohol use, cirrhosis, fatty liver disease etc), it’s more likely for you to get high cholesterol.

Non-alcoholic fatty liver disease (NAFLD), or commonly known as fatty liver, is the most common form of liver disease. It’s often seen among people who are overweight or have diabetes.

NAFLD can cause abnormal liver function and thereby cause high cholesterol. But at the same time, high cholesterol can cause excessive fat deposits to accumulate around the liver, forming what we called fatty liver.

Poor diet

Diet can affect your cholesterol levels in many different ways. First, 20% of the cholesterol comes from your diet. Eating saturated fat, found in animal products, and trans fats, found in some commercially baked cookies and crackers and microwave popcorn, can raise your cholesterol level. Foods that are high in cholesterol, such as red meat and full-fat dairy products, will also increase your cholesterol.

Some foods that are high in saturated fats or trans fats can also cause your liver to produce more cholesterol.

Also foods that are high in calories can cause obesity more easily, and as you will read later, obesity can cause cholesterol levels to go up too.

Lack of exercise

What happens when I exer
me when I exercise

Exercise helps boost your body’s HDL, or “good,” cholesterol while increasing the size of the particles that make up your LDL, or “bad,” cholesterol, which makes it less harmful.

Exercise often also helps to reduce obesity, another risk factor for high cholesterol.


Obesity can affect your cholesterol levels in many ways.

First, obesity increases the amount of LDL cholesterol your liver makes. It also decreases clearance of LDL cholesterol from your blood.

Second, excessive fats in the blood get deposited around the liver. This causes what we normally call the fatty liver. Fatty liver causes damage to the liver, and affects its efficiency in clearing out excessive cholesterol.

Third, insulin resistance. People who are obese are more likely to be less responsive to insulin. Insulin is a hormone released by the pancrease to convert extra sugar (glucose) into energy storage. Insulin resistance is the main cause of diabetes, which you will learn later, causes cholesterol levels to go up.


Smoking doesn’t just affect your lungs, it can also affect your cholesterol levels.

Cigarettes contain a host of toxins, including a particularly reactive chemical compound called acrolein. Acrolein is a yellow, foul-smelling vapor that is produced by burning plants, like tobacco. Acrolein is so toxic that it’s often used in pesticides.

Acrolein is easily absorbed into the bloodstream through the lungs and can “attack” the HDL (good cholesterol) and interfere with its ability to transport cholesterol back to the liver.


Diabetes are often associated with high cholesterol: People with diabetes are more likely to get high cholesterol, and people with high cholesterol often have diabetes.

What high cholesterol can do to your body

Heart and blood circulatory system

When you have too much LDL cholesterol in your body it can build up in your blood vessels, clogging them and making them less flexible. Blood doesn’t flow as well through stiff blood vessels, so your heart has to pump harder to push blood through them.

Narrowed blood vessels due to cholesterol buildups

Over time, this can lead to heart disease.

Building up of cholesterol in your blood vessels, also known as plague formation, can disrupt the flow of oxygen-rich blood to your heart. When your heart doesn’t get enough oxygen, angina (heart or chest pain) can occur. Angina is not a heart attack but it’s a warning sign that you are at risk of getting one.

Plague can continue to build up until the whole blood vessel is blocked, or a piece of the plague might come off and get transported to a smaller blood vessel and cause a complete blockade there. If the blocked blood vessel affected is the one going to the heart, you get a heart attack. If it is going to the brain, you will get a stroke.

Heart attack and stroke are highly dangerous situation. Blocked blood flow means interruption of oxygen supplies. Your most important organs cannot afford to have no fresh oxygen supply for too long.

Brain and Nervous system

The brain contains about 25 percent of the body’s entire supply of cholesterol. Cholesterol is essential for the development and protection of nerve cells, which enable the brain to communicate with the rest of the body.

Studies have suggested that high cholesterol may play a role in development of Alzheimer’s disease, a disease that causes the brain cells to degenerate and die.

Scientiests don’t know exactly what causes Alzheimer’s disease. But substances found in the brains of people with Alzheimer’s, called amyloid plaques, may be part of it.

Amyloid plaques form in the brain when a protein called beta-amyloid builds up.

And a recent study found that higher levels of LDL cholesterol and lower levels of HDL cholesterol both were linked to having more amyloid in the brain.

Digestive system

In the digestive system, cholesterol is essential for the production of bile – a substance that helps your body break down foods and absorb nutrients in your intestines.

But if you have too much cholesterol in your bile, the excess forms into crystals and then hard stones in your gallbladder. Gallstones can be very painful.