What is cholesterol?

Cholesterol is a fatty substance which is found in the blood. It is mainly made in the body. Cholesterol plays an essential role in how every cell in the body works. However, too much cholesterol in the blood can increase your risk of heart problems.

LDL cholesterol and HDL cholesterol

Cholesterol is carried around the body by proteins. These combinations of cholesterol and proteins are called lipoproteins. There are two main types of lipoproteins (classified by density):

• LDL (low-density lipoprotein) is the harmful type of cholesterol.
• HDL (high-density lipoprotein) is a protective type of cholesterol.

LDL carry cholesterol from the liver to cells of the body (ref) 1.019-1.063 g/ml
HDL collects cholesterol from the body's tissues, and brings it back to the liver. (ref) >1.063 g/ml HDL removes cholesterol from atheroma within arteries and transport it back to the liver for excretion or re-utilization—which is the main reason why HDL-bound cholesterol is sometimes called "good cholesterol", or HDL-C. (wiki)

Density (g/mL)	Class	Diameter (nm)	% protein	% cholesterol	% phospholipid	% triacylglycerol
>1.063	HDL	5-15	33	30	29	8
1.019-1.063	LDL	18-28	25	50	21	4

Lipoproteins in the blood, an aqueous medium, carry fats around the body. The protein particles have hydrophilic groups aimed outward so as to attract water molecules; this makes them soluble in the salt water based blood pool. Triglyceride-fats and cholesterol are carried internally, shielded from the water by the protein particle.

HDL are the smallest of the lipoprotein particles. They are the densest because they contain the highest proportion of protein. (wiki)

The American Heart Association, NIH and NCEP provides a set of guidelines for male fasting HDL levels and risk for heart disease. (wiki)

Level mg/dL	Level mmol/L	Interpretation
<40	<1.03	Low HDL cholesterol, heightened risk for heart disease, <50>
40–59	1.03–1.52	Medium HDL level
>60	>1.55	High HDL level, optimal condition considered protective against heart disease

Guidelines for fasting LDL-Cholesterol levels, estimated or measured, and risk for heart disease. As of 2003, these guidelines were:

Level mg/dL	Level mmol/L	Interpretation
<100	<2.6	Optimal LDL cholesterol, corresponding to reduced, but not zero, risk for heart disease
100 to 129	2.6 to 3.3	Near optimal LDL level
130 to 159	3.3 to 4.1	Borderline high LDL level
160 to 189	4.1 to 4.9	High LDL level
>190	>4.9	Very high LDL level, corresponding to highest increased risk of heart disease

source: wiki.

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Having too much harmful cholesterol in your blood can increase your risk of getting cardiovascular disease. The risk is particularly high if you have a high level of LDL cholesterol and a low level of HDL cholesterol.

Triglycerides

Triglycerides are another type of fatty substance in the blood. They are found in foods such as dairy products, meat and cooking oils. They can also be produced in the body, either by the body’s fat stores or in the liver. People who are very overweight, eat a lot of fatty and sugary foods, or drink too much alcohol are more likely to have a high triglyceride level.

People with high triglyceride levels have a greater risk of developing cardiovascular disease than people with lower levels.

What causes high cholesterol?

One of the causes of high blood cholesterol levels amount people in the UK is eating too much saturated fat. The cholesterol which is found in some foods such as eggs, liver, kidneys and some types of seafood eg. prawns, does not usually make a great contribution to the level of cholesterol in your blood. It is much more important that you eat foods that are low in saturated fat.
However, some people have high blood cholesterol even though they eat a healthy diet. For example, they may have inherited a condition called familial hyperlipidaemia (FH). For more information on FH, please download our booklet Reducing your blood cholesterol (see below under further information).

How can I reduce my cholesterol levels?

To help reduce your cholesterol level, you need to cut down on saturated fats and trans fats and replace them with monounsaturated fats and polyunsaturated fats. You should also reduce the total amount of fat you eat.
Eat oily fish regularly. Oily fish provides the richest source of a particular type of polyunsaturated fat known as omega-3 fats which can help to lower blood triglyceride levels and also helps prevent the blood from clotting, and help to regulate the heart rhythm.
Eat a high-fibre diet. Foods that are high in 'soluble fibre' such as porridge, beans, pulses, lentils, nuts, fruits and vegetables, can help lower cholesterol. Please see our fact sheet Fibre in our Any Questions/FAQ section.
Doing regular physical activity can help increase your HDL cholesterol (the 'protective' type of cholesterol).

Will eating sterol-enriched foods help reduce my cholesterol level?

There is evidence to show that substances called ‘plant sterols’ and ‘stanols’ may help reduce cholesterol levels. They are added to certain foods including margarines, spreads, soft cheeses and yoghurts. For more information please see our fact sheet Plant sterols and stanols in our Any Questions/FAQ section.