The determination of the level of cholesterol provides a physician with initial information regarding the state of a patients lipid metabolism. This information serves as a basis for further diagnostic measures, therapeutic decisions or monitoring of the progress of a patient.
Certain people should have a cholesterol blood test as part of a ‘cardiovascular risk assessment’.
These include: all people aged 40 or more, people at any age with a strong family history of early heart disease or stroke, and people at any age with a family history of a hereditary lipid (cholesterol) disorder. As a rule, no matter what your cholesterol level is, then lowering the level reduces your risk. Lifestyle factors that also reduce the risk include: not smoking, choosing healthy foods, a low salt intake, regular physical activity, keeping your weight and waist size down, and drinking alcohol in moderation. Your blood pressure is also important.
What is cholesterol?
Cholesterol is a lipid (fat chemical) that is made in the liver from fatty foods that we eat. A certain amount of cholesterol is present in the bloodstream. You need some cholesterol to keep healthy. Cholesterol is carried in the blood as part of particles called lipoproteins. There are different types of lipoproteins, but the most relevant to cholesterol are:
- Low density lipoproteins carrying cholesterol – LDL cholesterol. This is often referred to as ‘bad cholesterol’ as it is the one mainly involved in forming atheroma. Atheroma is the main underlying cause of various cardiovascular diseases (see below). Usually, about 70% of cholesterol in the blood is LDL cholesterol, but the % can vary from person to person.
- High density lipoproteins carrying cholesterol – HDL cholesterol. This is often referred to as ‘good cholesterol’ as it may actually prevent atheroma formation.
What are atheroma and cardiovascular diseases?
Patches of atheroma are like small fatty lumps that develop within the inside lining of arteries (blood vessels). Atheroma is also known as ‘atherosclerosis’ and ‘hardening of the arteries’. Patches of atheroma are often called ‘plaques’ of atheroma.
Over months or years, patches of atheroma can become larger and thicker. So, in time, a patch of atheroma can make an artery narrower. This can reduce the blood flow through the artery. For example, narrowing of the coronary (heart) arteries with atheroma is the cause of angina.
Sometimes, a blood clot (thrombosis) forms over a patch of atheroma and completely blocks the blood flow. Depending on the artery affected, this can cause a heart attack, a stroke, or other serious problems.
Cardiovascular diseases are diseases of the heart (cardiac muscle) or blood vessels (vasculature). However, in practice, when doctors use the term ‘cardiovascular disease’ they usually mean diseases of the heart or blood vessels that are caused by atheroma.
In summary, cardiovascular diseases that can be caused by atheroma include: angina, heart attack, stroke, transient ischaemic attack (TIA), and peripheral vascular disease. In the UK, cardiovascular diseases are a major cause of poor health, and the biggest cause of death.
What is a ‘high’ cholesterol level?
The following levels are generally regarded as desirable:
- Total cholesterol (TC) – 5.0 mmol/l or less. However, about 2 in 3 adults in the UK have a total cholesterol level of 5.0 mmol/l or above.
- Low-density lipoprotein (LDL) cholesterol after an overnight fast: 3.0 mmol/l or less.
- High-density lipoprotein (HDL) cholesterol: 1.2 mmol/l or more.
- TC/HDL ratio: 4.5 or less. That is, your total cholesterol divided by your HDL cholesterol. This reflects the fact that for any given total cholesterol level, the more HDL, the better.
As a rule, the higher the cholesterol level, the greater the risk to health.
However, your level of cholesterol has to be viewed as part of your overall cardiovascular health risk. The cardiovascular health risk from any given level of cholesterol can vary, depending on the level of your HDL cholesterol, and on other health risk factors that you may have.
Can diet lower my cholesterol level?
Changing from an unhealthy diet to a healthy diet can reduce a cholesterol level. However, dietary changes alone rarely lower a cholesterol level enough to change a person’s risk of cardiovascular disease from a high risk category to a lower risk. However, any extra reduction in cholesterol due to diet will help. A healthy diet has other benefits too apart from reducing the level of cholesterol.
Briefly, a healthy diet means:
- At least five portions, and ideally 7-9 portions, of a variety of fruit and vegetables per day.
- The bulk of most meals should be starch-based foods (such as cereals, wholegrain bread, potatoes, rice, pasta), plus fruit and vegetables.
- Not much fatty food such as fatty meats, cheeses, full-cream milk, fried food, butter, etc. Use low fat, mono-, or poly-unsaturated spreads.
- Include 2-3 portions of fish per week. At least one of which should be ‘oily’.
- Limit salt to no more than 6 g a day (and less for children).
- If you eat meat it is best to eat lean meat, or poultry such as chicken.
- If you do fry, choose a vegetable oil such as sunflower, rapeseed or olive oil.
- In addition, foods that contain plant sterols or stanols can reduce blood cholesterol level. For example, a daily dose of about 2 g of plant sterols or stanols can reduce LDL cholesterol by about 10%. Plant sterols and stanols are available in margarine spreads, yoghurts, milk drinks and other foods sold in stores. Food products containing plant sterols and stanols are generally designed to provide about one third of the recommended daily dose per meal. However, always read the labels and follow the manufacturer’s advice about portion sizes. Recommendations from the Food Standards Agency include the following:
- You should not not eat more than 3 g per day of plant sterols and stanols.
- Pregnant women, breast-feeding women, and children under the age of five years should not eat foods with added plant sterols or stanols.
- Foods with added plant sterols or stanols should be eaten as part of a balanced diet.