Cholesterol is found in every cell of the body and has important natural functions when it comes to digesting foods, producing hormones, and generating vitamin D. It is manufactured by the body but can also be taken in from food. It is waxy and fat-like in appearance.
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Fast facts on cholesterol
Here are some key facts about cholesterol. Find more detail and supporting information in the article.
- Cholesterol is an essential substance that is produced by the body but is also ingested from animal-derived foods.
- The greatest risk factors for high cholesterol are modifiable lifestyle choices - diet and exercise.
- Having high cholesterol does not produce any symptoms in itself.
- Everyone should have their blood cholesterol levels tested once every 5 years.
- If lifestyle changes are unsuccessful or cholesterol levels are very high, lipid-lowering drugs such as statins may be prescribed.
Cholesterol: Definition and meaning
Cholesterol is an oil-based substance and does not mix with the blood, which is water-based. It is carried around the body through the blood by lipoproteins.
Two types of lipoprotein carry the parcels of cholesterol:
- low-density lipoprotein (LDL) - cholesterol carried by this type is known as 'bad' cholesterol
- high-density lipoprotein (HDL) - cholesterol carried by this type is known as 'good' cholesterol
Cholesterol has four primary functions, without which we could not survive, these are:
- contributing to the structure of cell walls
- making up digestive bile acids in the intestine
- allowing the body to produce vitamin D
- enabling the body to make certain hormones
Causes of high cholesterol
Meat, cheese, and egg yolks are sources of cholesterol.
Elevated levels of LDL lead to a build-up of cholesterol in the arteries, whereas HDL carries cholesterol to the liver for removal from the body.
A build-up of cholesterol is part of the process that narrows arteries, called atherosclerosis, in which plaques form and cause restriction of blood flow.
Limiting intake of fat in the diet helps manage cholesterol levels. In particular, it is helpful to limit foods that contain:
- cholesterol (from animal foods, meat, and cheese)
- saturated fat (found in some meats, dairy products, chocolate, baked goods, and deep-fried and processed foods)
- trans fats (found in some fried and processed foods)
Being overweight or obese can also lead to higher blood LDL levels. Regular exercise may help manage this risk factor.
The primary causes of high cholesterol are genetic - very high LDL levels are found in the inherited condition familial hypercholesterolemia.
Abnormal cholesterol levels can also arise due to other conditions:
- liver or kidney disease
- polycystic ovary syndrome
- pregnancy and other conditions that increase levels of female hormones
- underactive thyroid gland
- drugs that increase LDL cholesterol and decrease HDL cholesterol (progestins, anabolic steroids, and corticosteroids)
Treatment and prevention of high cholesterol
Four changes to lifestyle are recommended for all people with high cholesterol levels in order to reduce the risk of coronary heart disease and heart attack:
- Eat a 'heart-healthy diet' (for example, use low-fat toppings and sauces, and avoid foods high in saturated fat; eat vegetables, fruits, and fiber-rich whole grains).
- Regular exercise.
- Avoid smoking.
- Achieve and maintain a healthy weight.
Drug treatment for an individual with hypercholesterolemia will depend on his or her individual cholesterol level and other risk factors.
Statin treatment is normally prescribed for people with a higher risk of heart attack. In general, diet and exercise are the first approach used to reduce cholesterol levels.
Statins are the leading group of cholesterol-lowering drugs; others include selective cholesterol absorption inhibitors, resins, fibrates, and niacin.
The statins available on prescription in the United States include:
- atorvastatin (brand named Lipitor)
- fluvastatin (Lescol)
- lovastatin (Mevacor, Altoprev)
- pravastatin (Pravachol)
- rosuvastatin calcium (Crestor)
- simvastatin (Zocor)
The prescription of statins has caused considerable debate in the medical community in recent years, with increased understanding of the side effects associated with these drugs.
While many patients benefit greatly from statin use to lower cholesterol and reduce their risk of heart attack, a significant number of patients also experience significant adverse effects from statins.
Side effects can include statin-induced myopathy (a muscle tissue disease) and fatigue, as well as a greater risk of diabetes and diabetes complications. Evidence from observational studies indicates that some 10-15 percent of statin users develop statin-related muscle side effects, such as myalgia and myopathy.
Switching to a different statin medication, or increasing efforts to reduce cholesterol through lifestyle changes may help relieve statin-induced myopathy and other unwanted effects of these drugs.
Lowering cholesterol: Diet and foods
A report from Harvard Health has identified "11 cholesterol lowering foods" that actively decrease cholesterol levels. Incorporating these into a balanced diet can help keep cholesterol in check:
Consuming fatty fish may help reduce cholesterol.
- barley and whole grains
- eggplant and okra
- vegetable oil (canola, sunflower)
- fruits (mainly apples, grapes, strawberries, and citrus)
- soy and soy-based foods
- fatty fish (particularly salmon, tuna, and sardines)
- foods rich in fiber
The same report also lists foods that are bad for cholesterol levels including:
- red meat
- full-fat dairy
- hydrogenated oils
- baked goods
High cholesterol symptoms
Having high cholesterol levels, while a risk factor for other conditions, does not itself present any signs or symptoms. Unless routinely screened through regular blood testing, high cholesterol levels will go unnoticed and could present a silent threat of heart attack or stroke.
Cholesterol tests, diagnosis, and complications
In the past, people have aimed to reduce cholesterol to a target level, for instance, below 100 milligrams per decilitre; this is no longer the case. There is no evidence from randomized, controlled clinical trials to support treatment to a specific target.
10-year risk of a heart attack
Cholesterol levels play a major part in an individual's risk of having a heart attack within the next 10 years. The National Heart, Lung, and Blood Institute provide an online calculator of cardiovascular risk. Using research evidence, it weighs the risk dictated by these factors:
- cholesterol levels
- smoking status
- blood pressure
Monitoring the 10-year risk according to data from the Framingham Heart Study, which continues today, helps in the management of lifestyle and other measures to reduce cholesterol levels, and so cut the chances of cardiovascular disease leading to heart attack or stroke.