Cholesterol

Written by: 
Dr Sarah Brewer

What is the difference between 'good' and 'bad' cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. and what are the effects on your health? This page explains.

Cholesterol is a waxy substance made in the liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. from certain dietary fats. You also obtain small amounts directly from some animal foods such as meat, egg yolks and prawns.

You need cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. to make healthy cellThe basic unit of all living organisms. membranes, bile acidsAny of a group of acids produced by the liver and present in the bile., vitamin D and steroid hormones such as oestrogenA hormone involved in female sexual development, produced by the ovaries. and testosterone.

In advising people on cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. in the diet, doctors distinguish between 'good' and 'bad' cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.. The main questions that arise are:

'Good' and 'bad' cholesterol

Cholesterol is insolubleA substance that cannot be dissolved.. The liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. combines it with protein to make soluble lipoproteins that transport cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. in your bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid..

There are two main types of cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.-containing lipoproteinOne of a group of compounds that consist of a protein combined with a lipid, and help to transport lipids in the blood and lymphatic system. particle:

  • Low-density lipoproteinOne of a group of compounds that consist of a protein combined with a lipid, and help to transport lipids in the blood and lymphatic system. (LDL)-cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.
  • High-density lipoproteinOne of a group of compounds that consist of a protein combined with a lipid, and help to transport lipids in the blood and lymphatic system. (HDL)-cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy..

These differ in the relative size and weight of the proteins they contain, but the cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. within them is the same.

'Bad' cholesterol

Low-density lipoproteinOne of a group of compounds that consist of a protein combined with a lipid, and help to transport lipids in the blood and lymphatic system. (LDL)-cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. is often referred to as 'bad' cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. because its particles are small enough to seep into arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. walls, causing them to 'fur up'. If you eat too few foods containing antioxidants, LDL-cholesterolSubstance that carries cholesterol around the bloodstream, a form of so-called 'bad cholesterol'. is readily oxidised and engulfed by scavenger cells (macrophages). When overladen with excess oxidised LDL-cholesterolSubstance that carries cholesterol around the bloodstream, a form of so-called 'bad cholesterol'., bloated cells become trapped in arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. walls. This contributes to the process of atherosclerosisDisease leading to fatty deposits in the inner walls of the arteries, which reduce and may eventually obstruct blood flow..

'Good' cholesterol

High-density lipoproteinOne of a group of compounds that consist of a protein combined with a lipid, and help to transport lipids in the blood and lymphatic system. (HDL)-cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. is referred to as 'good' cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. because it forms larger, heavier particles that are too big to seep into arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. walls or to be engulfed by scavenger cells.

HDL-cholesterolA substance that mainly exists to carry cholesterol from the circulation to the liver; commonly referred to as 'good cholesterol'. mops up excess cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. from the tissues and transports it away from your arteries and back to the liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. for processing. This protects against atherosclerosisDisease leading to fatty deposits in the inner walls of the arteries, which reduce and may eventually obstruct blood flow. and is known as reverse cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. transport.

Recommended cholesterol levels

A bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. test to measure cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels may be taken at any time - a random bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. sample. For a more accurate reading, cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels are best measured first thing in the morning, after you have fasted overnight for at least 12 hours. Because there is considerable day-to-day variation in levels, any treatment needed for raised cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels is usually based on the average of two or three different readings.

The test is often performed in a doctor's office or clinic. Many people have the test done annually as part of a routine check. People whose cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels are high and who are on medication and/or following a cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.-lowering programme usually have the test performed more often.

Although guidelines are regularly updated, it is generally accepted that ideally:

  • Your total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. should be less than 5 mmol/lMillimoles per litre - units of the amount of substance present. (190mg/dl)
  • Your LDL-cholesterolSubstance that carries cholesterol around the bloodstream, a form of so-called 'bad cholesterol'. should be less than 3 mmol/lMillimoles per litre - units of the amount of substance present. (115 mg/dl)
  • Your HDL-cholesterolA substance that mainly exists to carry cholesterol from the circulation to the liver; commonly referred to as 'good cholesterol'. should be greater than 1 mmol/lMillimoles per litre - units of the amount of substance present. (40mg/dl) for men, or 1.2 mmol/lMillimoles per litre - units of the amount of substance present. (46 mg/dl) for women.1

If your risk of a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. is high (for example, if you have established cardiovascular disease or have diabetes), the recommended total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. level is lower. For example, for high-risk individuals, European guidelines recommend:

  • Total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. should be below 4.5 mmol/lMillimoles per litre - units of the amount of substance present. (175mg/dl) and if possible less than 4 mmol/lMillimoles per litre - units of the amount of substance present. (155mg/dl)
  • LDL-cholesterolSubstance that carries cholesterol around the bloodstream, a form of so-called 'bad cholesterol'. should be less than 2.5 mmol/lMillimoles per litre - units of the amount of substance present. 100mg/dl) and if possible less than 2.0 mmol/lMillimoles per litre - units of the amount of substance present. (80mg/dl).1a

Controlling cholesterol in the diet

Maintaining a low total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. level and a high HDL-cholesterolA substance that mainly exists to carry cholesterol from the circulation to the liver; commonly referred to as 'good cholesterol'. level is associated with a reduced risk of cardiovascular disease.2

Usual advice to control cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels is to eat a diet that contains:

  • A total fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body. intake of 30 per cent or less of total energy intake
  • A saturated fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body. intake of 10 per cent or less of total energy intake
  • More monounsaturated fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body. and polyunsaturated fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body. in place of saturated fats
  • Less than 300mg dietary cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. per day - about the amount found in one large hen's egg
  • Five or more servings of fruit and vegetables per day
  • Two portions of fish per week, of which one is oily.3

Several studies have shown that eating one hen's egg per day does not increase the risk of coronaryRelating to the arteries supplying the heart itself. arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. disease or stroke.4,5 Read more about Fats in your diet

Controlling cholesterol levels with drugs

Some people inherit genes that mean their total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels cannot be controlled solely through diet and lifestyle changes, such as increased exercise. Drug treatment may be prescribed to reduce the risk of premature death, especially in people with other risk factors for heart disease such as smoking, high bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure, diabetes or being overweight.

The most widely prescribed cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.-lowering drugs are known as statinsA class of drugs that inhibit cholesterol formation in the liver.. Statins - for example, atorvastatin, fluvastatin, pravastatin, rosuvastatin and simvastatin - reduce cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. production in your liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. by inhibiting an enzymeA protein that speeds up chemical reactions in the body without being used up itself. (HMG-CoA reductase) that makes cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy..

Research suggests that taking a statinOne of a class of drugs that inhibit cholesterol formation in the liver. drug is associated with a 28 per cent reduction in the risk of recurrent heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction..6 Taking a statinOne of a class of drugs that inhibit cholesterol formation in the liver. may also reduce the risk of a stroke by up to 50 per cent.7

Initially, statinsA class of drugs that inhibit cholesterol formation in the liver. were prescribed for people at high risk of heart disease and stroke who had a raised cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. level.

However, the British Medical Research Council/British Heart Foundation (MRC/BHF) Heart Protection Study in 2002 showed that statinsA class of drugs that inhibit cholesterol formation in the liver. appeared to reduce the risk of major cardiovascular events in everyone, even in people with an ideal total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. level of <5.0 mmol/lMillimoles per litre - units of the amount of substance present..8

As a result, in many countries statinsA class of drugs that inhibit cholesterol formation in the liver. are now recommended for anyone at increased risk of heart disease. For example, in the UK they are offered to people whose likelihood of developing heart disease over the next 10 years is 20 per cent or greater.3 This risk is calculated from charts, based on your gender, age, smoking status, bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure, cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels and whether or not you have diabetes. The decision to prescribe a statinOne of a class of drugs that inhibit cholesterol formation in the liver. is no longer based on your cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. level alone.

Reducing statin side-effects

Around 10 per cent of patients treated with statinOne of a class of drugs that inhibit cholesterol formation in the liver. drugs experience some form of muscleTissue made up of cells that can contract to bring about movement.-related side-effect.9 This has been linked with the fact that, as well as switching off cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. production in the liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats., statinsA class of drugs that inhibit cholesterol formation in the liver. also switch off production of co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10. Taking a statinOne of a class of drugs that inhibit cholesterol formation in the liver. can halve your circulating bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. levels of co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10 within just 2 weeks.10

Co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10 is needed for energy production in cells, and is especially important in muscleTissue made up of cells that can contract to bring about movement. cells. Therefore when co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10 supplies are limited, muscleTissue made up of cells that can contract to bring about movement. side-effects may result.11,12

These side-effects may be reduced by taking a co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10 supplement.13 Taking a co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10 supplement has been shown to maintain bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. levels of co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10 without affecting the cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.-lowering effect of the statinOne of a class of drugs that inhibit cholesterol formation in the liver. drug.14

Co-enzymeA protein that speeds up chemical reactions in the body without being used up itself. Q10 supplements appear to be especially important for those on statinsA class of drugs that inhibit cholesterol formation in the liver. who have inherited raised cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. levels, known as familial hypercholesterolaemia, and for those with heart failureFailure of the heart to pump adequately. or who are over 65 years of age.15

References: 
  1. 'In patients with coronaryRelating to the arteries supplying the heart itself. heart disease on statinOne of a class of drugs that inhibit cholesterol formation in the liver. medication is there a lower limit for total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. when the statinOne of a class of drugs that inhibit cholesterol formation in the liver. should be stopped? Are there adverse effectsUndesirable side-effects of medication. of very low cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.?' National Public Health Service for Wales (Attract).
    1a. Fourth Joint Taskforce of the European Society of Cardiology and other Societies on Cardiovascular Disease Prevention in Clinical Practice. 'European guidelines on cardiovascular disease prevention in clinical practice'. Eur Heart J 2007; 28: 2375-2414. Link
  2. Everett CJ, Malnous AG III, Koopman RJ et al. 'Predicting coronaryRelating to the arteries supplying the heart itself. heart disease risk using multiple lipidOne of a group of compounds that are an important energy source. measures.' Am J Cardiol. 2005; 95(8): 986-988
  3. 'Quick reference guide: lipidOne of a group of compounds that are an important energy source. modification'. British National Health Service National Institute for Clinical Excellence (NICE). Link
  4.  Qureshi AI, Suri FK, Ahmed S et al. 'Regular egg consumption does not increase the risk of stroke and cardiovascular diseases.' Med Sci Monit. 2007; 13(1): CR1-8
  5. Nakamura Y, Iso H, Kita Y et al. 'Egg consumption, serum total cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. concentrations and coronaryRelating to the arteries supplying the heart itself. heart disease incidenceThe number of new episodes of a condition arising in a certain group of people over a specified period of time.: Japan public health center-based prospective study.' Br J Nutr. 2006; 96(5): 921-8
  6. Sheng X, Wei L, Murphy MJ et al. 'Statins and total (not LDL) cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. concentration and outcome of myocardial infarctionDeath of an area of heart muscle due to poor blood supply.: results from a meta-analysis and an observation study.' Eur J Clin Pharmacol. 2009;(Epub ahead of print). Link
  7. Gaspardone A, Arca M. 'Atorvastatin: its clinical role in cerebrovascular prevention.' Drugs 2007; 67(Suppl 1): 55-62
  8. Heart Protection Study Collaborative Group, 2002. Heart Protection Study of cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. lowering with simvastatin in 20,536 high-risk individuals: a randomised placebo-controlled trial. Lancet 2002;360:7-22. Link
  9. Venero V, Thompson PD. 'Managing Statin Myopathy.' Endocrinology and Metabolism Clinics of North America. 2009; 38(1): 121-36
  10. Rundek T, Naini A, Sacco R et al. 'Atorvastatin decreases the coenzyme Q10 level in the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. of patients at risk for cardiovascular disease and stroke.' Arch Neurol. 2004; 61(6): 889-92
  11. Lamperti C, Naini AB, Lucchini V et al. 'Muscle Coenzyme Q10 level in statinOne of a class of drugs that inhibit cholesterol formation in the liver.-related myopathy.' Archives of Neurology. 2005; 62: 1709-1712
  12. Littarru GP, Langsjoen P.  'Coenzyme Q10 and statinsA class of drugs that inhibit cholesterol formation in the liver.: Biochemical and clinical implications.' Mitochondrion. 2007; 7S: S168-174
  13. Caso G, Kelly P, McNurlan MA et al. 'Effect of coenzyme Q10 on myopathic symptoms in patients treated with statinsA class of drugs that inhibit cholesterol formation in the liver..' Am J Cardiol. 2007 May 15; 99(10): 1409-12
  14. Bargossi AM, Grossi G, Fiorella PL et al. 'Exogenous CoQ10 supplementation prevents plasmaFluid in which the blood cells are suspended. ubiquinone reduction induced by HMG-CoA reductase inhibitors.' Molecular Aspects of Medicine. 1994; 15S: S187-93
  15. Levy HB, Kohlhaas HK. 'Considerations for supplementing with coenzyme Q10 during statinOne of a class of drugs that inhibit cholesterol formation in the liver. therapy.' Ann Pharmacother. 2006; 40(2):290-4