Cholesterol is a lipid that circulates freely in the blood or takes part in building cell walls. The human body needs certain amounts of cholesterol to maintain important functions and processes, and for the synthesis of hormones, vitamin D and digestive enzymes. When cholesterol levels go outside the normal range, though, health problems begin.
That is why it matters to maintain optimal cholesterol levels and avoid the habits that raise them. But a healthy diet and lifestyle on their own are not entirely enough. The liver plays a key role here, because this organ is responsible for the metabolism and regulation of cholesterol in the body. In other words, if your liver is overloaded or in poor health, your cholesterol levels are very likely to be out of range too.
What raises cholesterol?
Although high cholesterol can be inherited, in most cases it is the result of an unhealthy diet and way of life. A healthy diet, regular exercise and certain supplements can help lower high cholesterol. But above all, you need to look after the health of your liver.
The liver is the largest internal organ in the body, in the upper right part of the abdomen. It is the main detoxifier of foreign substances and the chief regulator of many metabolic processes, including the metabolism of fats, carbohydrates and proteins. It also serves as a store for glycogen, fat-soluble vitamins and other important nutrients. Another very important function is the production and metabolism of cholesterol. So when normal liver function is impaired — whether by poor diet, an unhealthy lifestyle, illness or excessive use of medication — cholesterol levels begin to deteriorate too.
Inflammation as a cause of raised cholesterol
Chronic inflammation in the body can raise cholesterol levels, particularly LDL (the bad cholesterol). When there is inflammation, as in an infection or a chronic condition, the immune system activates processes that lead to raised cholesterol in order to support the repair of damaged tissue. This can lead to the build-up of cholesterol plaque in the blood vessels, which raises the risk of atherosclerosis (hardening of the arteries).
What does high cholesterol lead to?
Cholesterol in the body divides into two main kinds — "good", known as HDL (high-density lipoprotein), and "bad", known as LDL (low-density lipoprotein). Together they make up total cholesterol, which should not exceed 5 mmol/L. For the best results, aim to keep LDL relatively low (below 4 mmol/L) and HDL higher (above 1 mmol/L). Specialists recommend an LDL:HDL ratio in the order of 4:1.
High LDL levels raise the risk of fatty deposits in the vessels that carry blood to the heart muscle. Low HDL levels, on the other hand, suggest the body may not be able to clear plaque and other fatty deposits from the arteries. Both states — high LDL and low HDL — lead to a raised risk of heart disease.
High cholesterol, especially LDL, can damage the inner wall of the arteries. That damage can provoke an inflammatory response, in which the immune system begins to fight the accumulated plaque. The inflammatory process encourages the formation of new plaque, which can block the arteries and raise the risk of heart attack and stroke.
Inflammation can also be intensified by the presence of high cholesterol, through its influence on immune cells and on cell repair processes. This creates a vicious circle in which inflammation raises cholesterol and high cholesterol increases inflammation.
In short, inflammation and high cholesterol interact with one another and together increase the risk of cardiovascular disease. Controlling both is central to preventing these conditions.
High total cholesterol can set the stage for:
- metabolic syndrome
- high blood pressure
- heart attack
- stroke
How liver function and cholesterol are connected
Problems with the liver can interfere with its ability to produce or metabolise cholesterol. Both can lead to a rise in "bad" LDL cholesterol and affect your health negatively. The following liver conditions can lead to abnormal cholesterol levels:
- Non-alcoholic fatty liver disease — the most common form of liver failure (NAFLD). It affects roughly 25% of the world's population and is often seen in people who are overweight or have type 2 diabetes. The condition is associated with dyslipidaemia and unusually high cholesterol levels.
- Microvesicular steatosis — the accumulation of fat in liver cells, following the excessive use of certain medicines or other conditions such as Reye's syndrome, Alpers syndrome or Wolman disease.
- Hepatitis — inflammation of the liver, often caused by a virus. It divides into two main kinds: acute hepatitis (lasting less than 6 months) and chronic hepatitis (lasting more than 6 months). There are 5 different hepatitis viruses — A, B, C, D and E — and only forms B and C can become chronic.
- Cirrhosis — cirrhosis can prevent the liver from carrying out its basic metabolic functions. The condition is a reaction to long-term injury to the organ. After hepatitis C, long-term alcohol abuse is the most common cause.
How to improve the health of your liver
The liver plays a key role in the digestive system. Everything you eat or drink, including medicines and alcohol, passes through it. The organ helps purify the blood and is responsible for producing bile, which helps break down fats.
Some of the best advice for a healthy liver:
- limit alcohol, since the liver makes an enormous effort to deal with the toxins in alcoholic drinks;
- keep to a healthy diet rich in fruit, vegetables, pulses, seeds and nuts; drink at least 2 litres of water a day;
- take antioxidants;
- reduce processed and fatty foods, fried food, sugary and salty products and fizzy drinks;
- always ask your doctor how any prescribed medicine will affect your liver;
- use protection during sex;
- never share personal hygiene items such as toothbrushes, razors or combs;
- be careful during blood-taking procedures — check that hygiene conditions are good;
- wash your hands often and use hand sanitiser where appropriate;
- when handling dangerous chemicals such as insecticides, fungicides or paints, always wear a mask, gloves and long sleeves and trousers, since chemicals and toxins can enter the body through the skin;
- be physically active and keep to a healthy body weight.
Final words
The liver is the body's processing plant. It carries out a range of important functions, from producing proteins, bile and glucose to storing vitamins, minerals and carbohydrates and metabolising cholesterol. It also breaks down toxins, medicines and the natural by-products of metabolism. Keeping the liver in good shape is of first importance for the health of the whole body.
For a healthy liver and optimal cholesterol levels: be physically active, aiming for at least 30 minutes a day; eat well, with an emphasis on vegetables, fruit, pulses, seeds and nuts, and avoid fried food, sugary products, processed meat and fizzy drinks; keep a healthy weight with a body mass index between 18.5 and 24.9 kg/m² and a waist measurement under 88 cm for women and no more than 102 cm for men; drink at least 2 litres of water a day; sleep properly, aiming for at least 8 hours; avoid unnecessary stress and keep good personal hygiene.
This article is informational and does not replace consultation with a doctor.
Sources
- Arguello, G., Balboa, E., Arrese, M. & Zanlungo, S. (2015). Recent insights on the role of cholesterol in non-alcoholic fatty liver disease.
- Nemes, K., et al. (2016). Cholesterol metabolism in cholestatic liver disease and liver transplantation.
- Goldberg, A. C. (2015). Dyslipidemia. Merck Manuals.
- Prevention and Treatment of High Cholesterol (Hyperlipidemia). American Heart Association.
