What is Cholesterol

CHOLESTEROL

What is it? How do I find my cholesterol level? How do I reduce it?

One of the essential health messages of recent times is the importance of understanding cholesterol. However, few people know what it is, what is considered 'high', 'normal' or 'low' and if it is elevated what we should do about it.

What exactly is cholesterol?
Cholesterol has the consistency of a fatty or waxy substance. Chemically it is a sterol, which resembles a steroid, but with an additional alcohol group added to it.

Much of the necessary cholesterol required by the body is made by the liver from the saturated fats in our food and it has an important role to play in how every cell in the body functions. It is transported from the liver via the blood stream to the tissues. Fats such as cholesterol can be carried in the blood stream when they are soluble and that happens when they combine with lipoproteins. Lipoproteins are themselves combinations of fats and proteins.

Cholesterol is also present in some foods such as eggs, kidney, sea food (particularly prawns) and liver but consuming these items does not materially affect the circulating levels. Cholesterol is used to produce many of the body's natural steroid hormones. It is important for us all to be aware of our individual cholesterol level for too much cholesterol can increase the risk of getting coronary heart disease (CHD). If we know how the laboratory measures these levels and what these levels are we can make personal efforts to control it within the recognised safe range.

What are lipoproteins?
There are five major groups of lipoproteins but two of these are particularly important to be aware of: High Density Lipoproteins (HDL) and Low Density Lipoproteins (LDL).
Each has a different function in the body.
LDL carries cholesterol from the liver to be deposited around the body to fulfill the needs of the cells. LDL is referred to as 'bad cholesterol' because it conveys cholesterol out from the liver to the cells and, if not used up or removed, deposits cholesterol in the lining of the arteries. The more LDL there is in the circulation the more likely it is that heart disease will develop.
HDL carries the excess cholesterol from the cells and returns it to the liver for re-processing. HDL is frequently referred to as 'good cholesterol' because of what it does in removing excess cholesterol and raised amounts of HDL therefore provide some protection against heart disease.
What affects the levels of lipoproteins?
Men generally have higher levels of LDL compared to women and this is considered to be a result of the protective effect of one of the female hormones; oestrogen. This is reasoned because post-menopausal women begin to suffer from CHD in the same way as men.

The body produces more cholesterol if the diet is too high in saturated fat for this provokes the liver to produce more of it. There is an inherited predisposition to have a high cholesterol level and this is called Familial Hyperlipidaemia (FH). The incidence of this condition is about 1 in 500 people.

If there is a high level of cholesterol in the blood the lining of the arteries take up too much LDL and in the presence of high blood pressure this process is accelerated. This effect is greater in smokers or those with high blood pressure. Exercise, reducing saturated fat in the diet and modest levels of alcohol raises HDL levels and this helps reduce total cholesterol. The amount of cholesterol removed from the circulation is controlled by the demand at the cells and this too can be an indirect result of exercise. Where there is an inherited tendency to have a high level of cholesterol (FH) this is removed from the circulation at a much slower rate.

Why are we advised to reduce cholesterol?
If there is too much cholesterol in the circulation it gets deposited within the arteries and this narrows the internal diameter producing a roughening in the naturally smooth internal lining and restricts its ability to be flexible; to expand or contract to vary the blood flow within it. This causes the condition known as atherosclerosis. The formation of atheromatous plaque - rather like a wart on the inner lining of the artery - can become unstable, break down and expose certain lipid substances to the blood which cause blood to clot and break away into the blood stream.

The narrowing process diminishes the blood flow to the 'end organ' being supplied by the artery. If this happens to the arteries supplying the heart (the coronary arteries) it is known as angina. Being engaged in a form of exercise calls for a greater demand for blood supply to the heart muscle but if the coronary arteries are affected in this way only a restricted delivery of blood can be supplied and this results in the pain of angina. As the exercise is curtailed and the available circulation is able to satisfy the muscle's lower demand the pain is eased. When atherosclerosis occurs in the general circulation this is what is known as cardiovascular disease.

It follows that a high level of cholesterol is one of the key factors that can increase the risk of cardiovascular disease, angina, heart disease and stroke.

How to test for cholesterol?
Every adult should have their cholesterol levels measured and preferably before they are into middle age. If high cholesterol runs in a family, or if a close family member (blood relative) developed CHD before age 55 years for a man or 65 years for a woman, it is better to measure cholesterol at a much younger age - some time in the 20s.

The test for the total cholesterol (TC) level determines the overall level of cholesterol. This can be separated into the fatty substances of HDL, LDL and triglycerides (TG). This group of compounds is referred to as the 'blood lipids'. If the triglyceride level is higher than normal this also increases the risk of CHD.

The test is a simple process; either a finger prick sample, to provide a single drop of capillary blood, or a venous sample taken via a syringe. The finger prick test can provide a result from a desk top analyser in 2 minutes whereas the venous sample is sent to a laboratory and takes a few days. Such desk top analysers can perform a variety of processes such as Total Cholesterol (TC), LDL, HDL, triglycerides and a variety of other laboratory type tests.

A high level of cholesterol and triglycerides produces a greater risk of developing CHD. This is made worse if the level of HDL is too low and, correspondingly, the level of LDL is high. A higher level of HDL can be achieved through exercise and also by a reduction in dietary saturated fat.

The levels of cholesterol and other blood lipids vary day by day and even at different times of the day. Whereas a single high reading will bring this to an individual's close attention it is well worth checking this on a more routine basis to identify a trend and encourage self management of this through better dietary control or with the help of the family doctor with treatment, should that become necessary. If it is high, it may need regular re-testing to gauge the effect of diet or treatment. Good diet control can reduce it by 5 - 10%.

The UK is near the top of the international league of deaths from this disease and we need to do something about it. New information has revealed that young women, previously considered to have a degree of protection by virtue of the female hormones, are developing this disease in increasing numbers largely through the national increase in obesity.

There is good reason therefore for the general population to become much more informed about individual risks from high cholesterol levels in particular, for when people are empowered they are motivated to contribute to their own wellbeing. For these reasons the availability of simple-to-use self test kits to monitor these important values can provide the impetus to help safeguard the individual and influence the national statistics for the better. It is an excellent starting point.

A healthy diet can lower cholesterol.
Changing one's lifestyle by adjusting diet and increasing exercise can make a difference.
Eating too much saturated fats increase levels of LDL. Monounsaturated fats can reduce the LDL level without affecting the beneficial level of HDL. The polyunsaturated fats help reduce the level of LDL but unfortunately also reduce the level of HDL.

Doctors would like to see the general population reduce their overall intake of fats by 25% for this would not only help in avoiding CHD but also help control the national epidemic of obesity, which can lead to type 2 diabetes. Doctors also recommend oily fish which are higher in Omega - 3 fatty acids which help reduce the triglyceride levels for this reduces the risk of blood clot formation. The Omega - 3 fatty acids are found in fish oil from fresh herring, mackerel, sardines, salmon, trout and tuna.

What are the target levels of cholesterol?
There can be few people who have not received the message that we need to reduce levels of cholesterol. Since this is one of the high risk factors for CHD it is important that individuals are well prepared to deal with the results and make efforts to alter them for the better.

The measurements are made in laboratory units called millimols per litre of blood and this is usually shown as mmol / L. The target range is:

A total cholesterol (TC) level of less than 5 mmol / L
An HDL level of more than 1 mmol / L
An LDL level of less than 3 mmol / L
A triglyceride level of less than 2 mmol / L

In addition doctors consider the ratio of TC : HDL, as a quick guide of acceptability - by dividing the Total cholesterol result by the HDL result - and this should be less than 4.5. This can be adjusted by the individual by increasing the amount of HDL generated through exercise. It will be appreciated that if the HDL level is increased by exercise this will reduce TC : HDL ratio - hence one of the benefits of exercise. Similarly, if the TC level is low a good level of HDL will produce a good TC : HDL ratio of less than 4.5.

The family doctor or practice nurse will advise what to do if an individual's results are of concern. It is likely that diet and exercise will be suggested as an early option and if, perhaps after correcting an unhealthy diet, repeat test results provide evidence that the cholesterol levels remain elevated, further advice on other options should be obtained from the family doctor.

Statins
Since their introduction over ten years ago and following extensive trials, the statin group of drugs have proved their worth in reducing cholesterol, for whereas dietary control can reduce levels by between 5 - 10% the statins can achieve a 20% reduction making their contribution as a life saving form of treatment highly valued. To combat our national statistics it has even been suggested that the use of these drugs should be applied on a more liberal basis.

The stated list of side effects associated with statins appears daunting, but it should be noted that all side effects identified during the clinical trials phase must be catalogued. In practice however the drug is well tolerated and benefits outweigh side effects. They are not suitable for all people; such as those with liver and, like most other drugs, pregnancy or breast feeding.

Risk factors in perspective
The individual risk factors and their contribution to this disease are taken from all people who died from CHD under age the age of 75:

High blood cholesterol - 46%
Lack of exercise - 37%
Smoking tobacco - 19%
High blood pressure - 13%
Obesity - 6%

(Acknowledgement. Figures by the British Heart Foundation.)

It is clear from these statistics that exercise (to increase HDL) and diet - effectively a change in lifestyle - could make a major contribution to correcting our CHD national statistics by controlling these damaging lipids.

The more risk factors an individual has the higher the risk of CHD.

By courtesy of: Egohealth Limited
www.egohealth.co.uk