What is Cholesterol?

We hear a lot about cholesterol day-to-day in the news, online or during conversations with friends and family (especially elderly relatives!) and despite this, not many of us actually know what cholesterol is and what all the fuss is about!
Cholesterol is a fatty substance, carried around the body, which plays a variety of important roles in the body including:

  • building blocks of hormones such as vitamin D, oestrogen, progesterone, testosterone and cortisol
  • building the structure of cell membranes
  • helping the liver to create bile, which aids in digestion and our ability to digest fats and nutrients
  • helping the body to heal from injuries and helps the body fight infections – exactly what we need this time of year!
  • aiding brain function – as cholesterol is found in large amounts in brain tissue

As you can see, cholesterol is a very necessary substance and it’s probably hard to understand why cholesterol gets so much bad press. This can be explained by the fact that when we have too much of the ‘wrong’ kind of cholesterol and too little of the ‘good’ kind, we are at a higher risk of cardiovascular disease (CVD), explained further below.

Where does cholesterol come from?

While there is cholesterol present in some of the foods we consume (for example eggs, dairy, meat and organ meats), about 80% of the cholesterol in our body is made by the liver.

How is cholesterol transported around the body?

Cholesterol is transported through the bloodstream in vehicles (just like passengers in a car on a highway) called ‘lipoprotein particles’. The main types of lipoproteins include:

Chylomicrons and very-low-density lipoproteins (VLDLs) – transport cholesterol to tissues for storage or to the muscles for energy. VLDLs break down to low-density lipoproteins and as you will read, this is not an ideal situation when created in excess.

Low-density lipoproteins (LDLs) – transports cholesterol to tissues to be used to create hormones, cell membranes, bile salts etc. LDLs are often referred to as ‘bad’ cholesterol because when we have more LDL than we need, LDLs deposit leftover cholesterol in the arteries, which can restrict blood flow and lead to atherosclerosis.

High-density lipoproteins (HDLs) – remove excess cholesterol from the tissues and carry it back to the liver where it can be re-used or removed from the body. This form of cholesterol is considered ‘good’ because it carries cholesterol away from the heart, which reduces the risk of cholesterol being deposited in the arteries. Too little HDLs can also contribute to atherosclerosis.

What is the problem with too much ‘bad’ cholesterol?

As discussed, too much LDL-C and also too little HDL-C in the blood can form plaques that can narrow or block arteries – referred to as atherosclerosis. Arteries are responsible for carrying oxygen and nutrients via the blood from the heart to the rest of the body. This means, if arteries become blocked, blood flow to organs and tissues is restricted and this can eventually lead to a heart attack, heart failure or stroke – these conditions fall under the collective term CVD. Sadly, CVD is responsible for 1 death in Australia every 12 minutes.

Triglycerides, which you may have heard of when talking about cholesterol, are also a form of fat found in the blood. Triglycerides are mostly produced when we consume more kilojoules/calories (energy) then needed and are stored in fat cells. They can also be produced from underlying health conditions. Similar to cholesterol, excess triglycerides are known to form fatty plaques in the arteries and are therefore also a risk factor for CVD.

What are the risk factors for high ‘bad’ cholesterol?

Just like most things in life, there are things we can control and things we cannot control! The situation is similar when it comes to cholesterol – there are both non-modifiable risk factors and modifiable risk factors:

Non-modifiable – factors mostly out of our control:

Age – as we get older, cholesterol levels tend to rise but this is more common in men. This means getting on top of the modifiable risk factors at an early age is important.

Gender – men are at a higher risk of high cholesterol until women reach menopause. This means if you are female and have recently gone through menopause, it’s important to get your cholesterol measured as a preventative measure.

Genetics – the way our body handles cholesterol is genetically determined and an error in genes can lead to increased cholesterol levels. This means if other family members have high cholesterol, it may be important to have yours checked also. 

Modifiable: thankfully there are many risk factors within our control, including:

Lack of physical activity and a sedentary lifestyle – being physically active can help to increase HDL-C and reduce other risk factors for CVD such as blood pressure, assist with weight management and blood sugar control which in turn will impact cholesterol.

Smoking – smokers have lower concentrations of HDL-C, higher LDL-C and triglycerides compared to people who don’t smoke and quitting smoking alone is associated with an increase in HDL-C.

Obesity – can increase LDL-C levels and lower HDL-C due to increased stimulation of VLDLs.

Excessive alcohol intake – a moderate amount of alcohol can actually be beneficial to cholesterol levels. However a high consumption of alcohol can negatively impact blood lipids and this may in part be due to the increased kilojoule/calorie load associated with consuming alcohol and also the impact drinking alcohol can have on our dietary choices.

Hypothyroidism (low thyroid function) – a disease, which is more commonly experienced by women and is linked to increased total cholesterol and LDL-C due to a reduced ability of the body to clear LDL-C.

Metabolic syndrome and type 2 diabetes – people with diabetes and/or metabolic syndrome are more likely to have higher LDL-C than those who don’t. This is because an inability to manage blood glucose levels can inhibit the clearance of LDL-C.

Diet – while only a very small amount of the cholesterol we consume in foods impacts our cholesterol levels, eating a diet high in refined sugar, trans fats and saturated fats have been found to negatively impact cholesterol and triglyceride levels. If you aren’t familiar with the main kinds of fats or which foods fall under each kind of fat, here is an overview: 

Trans fats (hydrogenated fats or partially hydrogenated fat): a cheap source of fat and not a good form of fat, sources include fried foods, heated fats/oils & hidden in some biscuits, cakes, bread, muffins, dried fruit & muesli/cereals.

Saturated: found in animal, dairy, coconut milk and coconut oil products. Not as harmful as trans fats but should only be consumed in moderation.

The two main kinds of healthy fats, which may offer protection against elevated LDL-C cholesterol and triglycerides include:

Monounsaturated:  found in olive, canola and peanut oils, avocado and nuts especially macadamia nuts.

Polyunsaturated: found in vegetable oils, flaxseeds, nuts and seed, fish

2 main types of essential fatty acids:

  • Omega 3: EPA/DHA – oily fish (salmon, sardines, anchovies, cod, mackerel) and ALA – flaxseed seeds/oil, walnuts, chia seeds and hemp seeds.
  • Omega 6: vegetable and seed oils.

How can I find out what my cholesterol levels are?

There are no ‘symptoms’ of high cholesterol so to check your levels, a GP or specialist can order a fasting lipid profile via a blood test. This test will show total cholesterol, HLD-C, LDL-C and triglycerides. Your results will be compared to the below general measures:

  • Total Cholesterol
  • Desirable: below 4.0mmol/L
  • High: 5.5-6.5mmol/L
  • High risk: above 6.5mmol/L

HDL (‘good’ cholesterol)

  • Desirable: greater than 1.0mmol/L

LDL (‘bad’ cholesterol)

  • Desirable: below 2.0mmol/L
  • High risk: greater than 2.0mmol/L


  • Desirable: below 2mmol/L
  • High risk: greater than 2mmol/L

Once you have found out the results of your lipid profile, you will then have some insight into your level of risk for CVD. Understandably, this is important information to have, considering CVD is Australia’s leading cause of death. Thankfully, there are many modifiable risk factors which can be put into practice and further research in this area, including the use of nutraceuticals, is being undertaken which will offer further possibilities when it comes to the prevention of high cholesterol, CVD and improving overall well-being generally.

Curious about your cholesterol levels?

Do you have, or think you have elevated cholesterol? Visit us for a free cholesterol test and check your eligibility for our study.