What is cholesterol?
High cholesterol increases your risk of heart disease, but a certain amount of cholesterol is actually essential for your metabolism. Cholesterol is used:
- as a building block for all cell membranes
- to produce hormones like oestrogen and testosterone
- to produce bile acids that are essential for digestion and absorption of nutrients
- to help your body produce vitamin D.
Cholesterol is a combination of lipid (fat) and steroid that is naturally produced by the body. About 80 per cent of the body’s cholesterol is produced by your liver, while the rest comes from your diet. After a meal, your body absorbs the cholesterol in your food and stores it in your liver. Your liver is able to regulate cholesterol levels in your blood and can secrete cholesterol if required.
What are the effects of high cholesterol levels?
High cholesterol is a condition called hyperlipidaemia. Too much cholesterol circulating in your blood can lead to fatty deposits developing in your the arteries. This causes your blood vessels to narrow and eventually get blocked, which can then lead to heart disease and/or stroke.
What is HDL and LDL cholesterol?
Cholesterol is carried around the body by lipo-proteins called LDL and HDL.
LDL (low density lipo-protein) cholesterol is often referred to as the “bad” cholesterol, because elevated levels of LDL cholesterol are associated with an increased risk of coronary heart disease, stroke, and peripheral artery disease.
LDL deposits cholesterol along the inside of artery walls, causing the formation of a hard, thick substance called cholesterol plaque. Over time, cholesterol plaque causes a thickening of the artery walls and narrowing of the artery passages. This process is called atherosclerosis and is dangerous as it decreases blood flow due to the narrowed area. High levels of LDL cholesterol and low levels of HDL cholesterol (often called a “high LDL to HDL ratio”) is a risk factor for developing atherosclerosis.
HDL (high density lipoprotein) cholesterol is known as the “good cholesterol” because HDL cholesterol particles prevent atherosclerosis by extracting cholesterol from the artery walls and disposing of it through the liver. Low levels of LDL cholesterol and high levels of HDL cholesterol (called a “low LDL to HDL ratio”) is desirable as it protect against heart disease and stroke.
Total cholesterol is considered the sum of LDL cholesterol, HDL cholesterol, VLDL (very low density) cholesterol, and IDL (intermediate density) cholesterol.
What determines the level of LDL cholesterol in my blood?
Factors that affect your blood cholesterol levels include diet, body weight, exercise, age and gender, diabetes, heredity, and other causes including underlying medical conditions.
Diets that are high in saturated fats raise the levels of LDL cholesterol in the blood. Fats are classified as saturated or unsaturated (according to their chemical structure).
Part 2 of this article series provides additional information about cholesterol, including tips to lower your cholesterol level.
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Disclaimer: This article provides general advice only. Readers should seek independent professional advice from their general practitioner or dietitian in relation to their own individual circumstances or condition before making any decisions based on the information in this article.