Cholesterol is both our friend and foe - at normal levels, it is an essential substance for the body's normal functioning, but if levels in the blood get too high, it becomes a silent danger that puts us at risk of a heart attack.
Contents of this article:
- What is cholesterol?
- What causes high cholesterol?
- Signs and symptoms of high cholesterol
- Cholesterol tests and diagnosis
- Treatment and prevention of high cholesterol
- Lipid-lowering therapy
- Ten-year risk of a heart attack
What is cholesterol?
Cholesterol is a fatty, waxy substance that is mainly produced by our liver.
What we eat can contribute to high blood cholesterol, so it is important to
follow a heart-healthy eating pattern. Eating foods with more unsaturated
fats in place of saturated or trans fats and avoiding refined carbohydrate
foods can help improve cholesterol levels.
Saturated and trans fats are found in higher amounts in animal
products like butter, cheese, processed or fatty meats (like ham,
salami, sausage); as well as in deep fried foods, pies, pastries,
biscuits and cakes.
Apart from the effect of certain foods, high blood cholesterol
levels can also be due to a genetic (inherited) disorder.
Whatever the cause of your high cholesterol, it is important to
lower your levels through lifestyle changes and/or medication.
What does cholesterol do?
Cholesterol is important as it helps our bodies function properly.
However, if there is too much cholesterol in your blood, it will build
up in your artery walls, causing narrowing of the arteries. This
increases your risk of developing heart disease or having a stroke.
Cholesterol and other fats are called lipids. There are different types of lipids
within our body. Each has a different function:
• High Density Lipoprotein cholesterol (HDL) is often called the ‘good’
cholesterol because it helps remove cholesterol from the artery walls.
This reduces your risk of heart disease.
•Low-Density Lipoprotein cholesterol (LDL) is often called the ‘bad’
cholesterol because it deposits cholesterol into the artery walls.
This increases your risk of heart disease.
• Triglycerides are the most common form of fat in our body. They are
a storage form of energy for the body. High triglyceride levels are
associated with many diseases, including heart disease and stroke.
Cholesterol is found in every cell of the body and has important natural functions. It is manufactured by the body but can also be taken in from food. It is waxy and fat-like in appearance.1-3
Cholesterol is oil-based and so does not mix with the blood, which is water-based. It is therefore carried around the body in the blood by lipoproteins.1-3
The parcels of cholesterol are carried by two types of lipoprotein:2
- 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 main functions, without which we could not live. It:1,3
- Contributes to the structure of cell walls
- Makes up digestive bile acids in the intestine
- Allows the body to produce vitamin D
- Enables the body to make certain hormones.
Recent developments on cholesterol from MNT news
Dementia health also affected by cholesterol levels. The balance of LDL and HDL cholesterol levels is important not just for heart health but for brain health too, according to a December 2013 study. The research, published in JAMA Neurology, found that control of cholesterol reduced the brain plaques linked to Alzheimer's disease.
High cholesterol linked to infertility - prospective parents with high cholesterol levels could be in for a long wait to become pregnant, a new study published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism states.
Study links high LDL cholesterol to aortic valve disease - a study published in JAMA claims to have found evidence to support a causal association between high levels of "bad" cholesterol and aortic valve stenosis - a form of aortic valve disease in which the valve is narrowed, restricting blood flow from the heart.
The support charity for people with high cholesterol, HEART UK, has identified "six super foods" that actively lower cholesterol levels:
- Soya foods (15g a day) - soya milk, soya desserts, soya meat alternatives, soya nuts, edamame beans and tofu
- Nuts - a handful a day
- Oats and barley - providing the soluble fiber beta glucan
- Plant sterols/stanols - found in a wide range of foods
- Fruits and vegetables
- Foods rich in unsaturated fats - for example, canola and vegetable oils.
lists foods that are bad for cholesterol levels:
- Hard margarines
- Fatty and processed meat
- Dairy fats.
What causes high cholesterol?
High cholesterol or hypercholesterolemia is also known as hyperlipidemia and dyslipidemia.4 It is a major risk factor for coronary heart disease, a cause of heart attacks, and reducing blood lipid levels lowers the cardiovascular risk.4
High 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.2 A build-up of cholesterol forms part of the process that narrows arteries, called atherosclerosis, in which plaques form and cause restriction of blood flow.2
Two types of cause lead to high cholesterol levels - modifiable and non-modifiable risk factors. The major two risk factors are highly modifiable - something can be done to change them:2
- Exercise and weight.
Limiting intake of fat in the diet helps manage cholesterol levels, limiting foods, in particular, that contain:2
Meat, cheese and egg yolks are sources of cholesterol.
- Cholesterol (from animal foods, such as egg yolks, meat and cheese)
- Saturated fat (found in some meats, dairy products, chocolate, baked goods, and deep-fried and processed foods)
- Trans fat (found in some fried and processed foods).
Being overweight or obese can lead to higher blood LDL levels so exercise can help manage this risk factor.2
The primary causes of hyperlipidemia are genetic - very high LDL levels are found in the inherited condition familial hypercholesterolemia.5 Other genetic conditions passed down from parents are: familial combined hyperlipidemia, familial dysbetalipoproteinemia and familial hypertriglyceridemia
Abnormal cholesterol levels may also be secondary to the following:5,6
- 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).
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 available from foods.
- The greatest risk factors for high cholesterol are modifiable lifestyle choices - diet and exercise.
- High cholesterol levels can be inherited with the genetic condition, familial hypercholesterolemia.
- Having high cholesterol does not produce any symptoms.
- Cholesterol levels should be blood-tested once every five years.
- First-line ways to reduce cholesterol involve lifestyle changes.
- If lifestyle changes are unsuccessful or cholesterol levels are very high, lipid-lowering drugs such as statins may be prescribed.
- High cholesterol levels are an important contributor in the calculation of an individual's risk of having a heart attack within the next ten years.
Signs and symptoms of high cholesterol
Having high cholesterol levels, while a risk factor for other conditions, does not itself present any signs or symptoms.2,7 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 and diagnosis
High cholesterol can only be diagnosed by blood testing. Doctors' guidelines state that everyone over the age of 20 years should have their cholesterol levels checked once every five years.6
The cholesterol test is done after a period of fasting - no food, drink or pills for 9 to 12 hours - to enable an accurate reading of LDL cholesterol from the blood test.8 The screening also gives information about total cholesterol, HDL cholesterol and triglyceride levels.
The guidelines set chole