Cholesterol is an essential type of fat that is carried in the blood – but too much of a certain type of cholesterol may increase your risk of developing heart disease. We asked our researchers to provide insight into cholesterol.

Understanding cholesterol: How good lifestyle practices can help keep your cholesterol in check

Firstly, what is cholesterol?

Cholesterol is an essential type of fat that's carried in the blood.

All cells in the body need cholesterol; it's an essential part of cell walls in our bodies and has important roles, including to produce some hormones, maintain healthy nerve cells and in the synthesis of vitamin D.

Your body needs a small amount of cholesterol to function, but an imbalance between different types of cholesterol in the blood increases the risk of heart disease, one of the leading chronic diseases in Australia today.

About ¾ of the cholesterol in your body is made in the liver and a small amount may come from the food you eat. Various factors affect blood cholesterol levels including your diet and lifestyle, body weight and genes.

Why is high cholesterol a problem?

Too much cholesterol in the bloodstream can harden arteries and promote fatty deposits within these arteries, potentially leading to dangerous blockages and narrowing over time called atherosclerosis.

A diagram showing a normal artery with normal blood flow and an artery containing plaque build-up.

This diagram shows a normal artery with normal blood flow (Figure A) and an artery containing plaque build-up (Figure B).  © Wikimedia Commons

If the blood vessels leading to your heart become too clogged, blood supply to your heart is reduced, which can lead to symptoms such as angina (chest pain). If the artery becomes completely blocked, it can lead to a heart attack and stroke, which can be life threatening.

In 2017, the Australian Bureau of Statistics reported 43, 477 deaths in Australia from heart disease. This is approximately 30 per cent of all deaths in Australia, and most deaths are occurring in those aged 65 years and over.

However, heart disease takes years to develop, so you can take steps to reduce your risk. If you discover you have high cholesterol, have family members with high cholesterol, or are not sure if you're at risk, it is advisable you seek your doctor's advice.

Other risk factors for heart disease include increased age, ethnicity, family history, inactivity, smoking, high blood pressure, type 2 diabetes and obesity. If these risk factors are present in your life, it's even more important to keep your blood cholesterol levels in check and seek your doctor's advice.

The Australian Absolute Risk Calculator can help you begin to assess your risk, but we strongly advise you discuss your risk with your GP as this tool does have limitations; it doesn't take your family history into account, for example. 

Cholesterol and heart disease risk

People aged 45 years and older are encouraged to have their cholesterol and risk for heart disease assessed. Aboriginal and Torres Strait Islanders are encouraged to have this assessment done from the age of 35 years and older.

Cholesterol - the good and the bad

Fats, including cholesterol, combine with proteins to form lipoproteins. It is in this form that the fats are carried by the blood.

Lipoproteins can be separated into different types depending on their density, into Low Density Lipoproteins (LDLs) and High Density Lipoproteins (HDLs), commonly known as the good and the bad cholesterol.

You may want to think of LDLs as lousy cholesterol, as these particles, if present in too high amounts, proliferate in the arterial wall leading to the development of atherosclerosis and heart disease.

HDLs can be thought of as the helper cholesterol, as these particles help to protect against heart disease. HDLs help to remove the fatty deposits in the arteries and take them to the liver for destruction and removal from the body.

Having a low HDL level in the blood can be directly linked to an increased risk of coronary heart disease.

What about triglycerides?

Triglycerides are another common source of fat found in the bloodstream, which provide a major source of energy. If you consume more energy (kilojoules/calories) from foods and beverages than what you need throughout the day, this energy is converted into triglycerides by the liver and stored within fat cells, ready for use later.

If you are consistently eating more energy than you burn, over time it is likely that you will have high triglycerides.

High triglycerides can lower levels of HDL and increase heart disease risk and have been linked to atherosclerosis and inflammation of the pancreas.

The good news is that you can lower your triglycerides rapidly through dietary changes.

What's considered as normal cholesterol levels?

Many factors influence what your personal cholesterol or lipid targets should be, and so cholesterol tests should be interpreted in the context of your personal risk.

Your doctor can help you understand your results and guide you on strategies to not only lower your cholesterol but lower your risk of heart disease.

The Reducing Risk in Heart Disease, expert guide to clinical practice for secondary prevention of coronary heart disease, 2012 [pdf · 715kb]  and the Guidelines for preventive activities in general practice, 9th Edn [pdf · 2mb] provide general goals for Cholesterol/ Lipid targets, these are:

  • Total Cholesterol: <4.0 mmol/L (Individuals at high risk) <5.5 mmol/L (General population)
  • Low Density Lipoprotein Cholesterol (LDL): < 1.8mmol/L (Individuals at high risk) < 2.0 mmol/L (General population)
  • High Density Lipoprotein Cholesterol (LDL): > 1.0mmol/L
  • Triglycerides (TG): < 2.0 mmol/L.

Guidelines also suggest that that all patients presenting with elevated Total and LDL cholesterol are to be provided with healthy eating and lifestyle advice – the first line approach in working towards improving your cholesterol levels.

Cholesterol in foods and your diet

Cholesterol present in food is referred to as dietary cholesterol. However, cholesterol in food is less important than getting the right balance of dietary fats. Why?

Dietary cholesterol has only a small influence on LDL cholesterol. Instead, the saturated fats in your diet is what raises LDL cholesterol by the liver.

Healthy fats, such as unsaturated fats, help to balance your blood cholesterol through reducing LDL cholesterol and increasing production of HDL cholesterol.

Not many foods contain dietary cholesterol, these are offal (such as liver and kidneys), pate, egg yolks and prawns. As many of these foods are not consumed in high amounts, you can still include them within in a balanced wholefood diet in infrequent, small amounts.

What can I do NOW to improve my cholesterol?

Years of research has identified various dietary strategies you can adopt to improve your cholesterol levels and reduce your risk of heart disease.

These are:

Avocado and nuts are examples of healthy unsaturated fat sources to include in your diet  © Pexels

  • Cutting back on discretionary foods: foods high in sugar, salt and fat and low in nutrients, such as cakes, pastries, biscuits, ice-cream and flavoured beverages.
  • Including healthy unsaturated fat sources in your diet every day, such as avocado, nuts, seeds, vegetable oils such as olive oil, canola oil, flax seed oil and vegetable-based spreads. Include a hand-full of nuts and seeds in your diet every day.
  • Consuming fish, particularly fatty fish types, aiming for about 2-3 servings per week.
  • Including fibre-rich foods (wholegrain) into your diet daily, in particular foods containing soluble fibre, such as β-glucan from oats, psyllium, legumes.
  • Including soy protein into you diet, such as soy milk and soy cheese.
  • Increasing your intake of vegetables and fruit, aim for five vegetable and two fruit serves per day.
  • Including, where you can, plant sterol enriched food sources, such as margarine containing plant sterol and Weetabix. 2g/day of plant sterols will reduce total cholesterol by 10-15 per cent.
  • Balancing saturated and unsaturated fatty acid sources.

Notes

  1. BS 2018: Causes of Death 2017 ABS cat no. 3303.0 ABS 2012,
  2. National Health Survey, 2011/2012 . ABS cat. No. 4364.0.55.00

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