Cholesterol is a fatty substance found in body cells of humans and animals. Cholesterol is required for the formation of bile acids which are needed for fat digestion. It is also used to make important hormones such as natural steroids and sex hormones. It is essential in forming the membranes of cells in the body and is involved in the formation of vitamin D in the skin.

Your body requires a certain amount of cholesterol to keep itself healthy. Some of this might come from dietary cholesterol, but the body is capable of making its own cholesterol if the dietary intake is low. So, cholesterol in the body comes from two sources. Foods of animal origin, such as meat, milk, and eggs, are one source. However, the major source of cholesterol is that which is produced by your own body. Eating saturated fats (the major source being animal fats) encourages your body to make more cholesterol. Being overweight also contributes to this tendency.

High levels of cholesterol are bad

Whilst cholesterol is an essential for normal health we know that excess levels of cholesterol cause disease in blood vessels. Excess cholesterol is deposited in the walls of blood vessels and eventually they become narrowed causing obstruction to blood flow. This leads to angina (heart pain) and claudication in the legs (muscle pain due to inadequate oxygen supply). Eventually, further narrowing or a blood clot will lead to blockage of the blood vessel and the end result is a stroke, a heart attack or an amputated leg.

"Good" cholesterol

Cholesterol is further divided into "good" cholesterol and "bad" cholesterol. Actually these descriptions refer to the substances, called lipoproteins, that carry cholesterol throughout the body in the bloodstream. Lipoproteins are a combination of varying amounts of fats and proteins.

"Good" cholesterol is associated with high density lipoproteins (HDLs). HDLs remove excess cholesterol from the body by transporting it to the liver where it is disposed of. Therefore, higher levels of HDLs are associated with lower rates of heart disease. You can increase your HDL by exercising.

"Bad" cholesterol

"Bad" cholesterol is associated with low density lipoproteins (LDLs). LDLs carry cholesterol in the blood to body cells. High levels of LDLs are usually associated with an elevated total blood cholesterol and an increased risk of heart disease due to cholesterol and fat being deposited in the arteries, causing narrowing of the arteries.

Dietary fat

Dietary fats are made up of three types of fatty acids: saturated, mono-unsaturated and polyunsaturated. Fats containing a large amount of saturated fatty acids are hard at room temperature; less saturated fats are soft or liquid at room temperature. Thus, beef fat is more saturated than chicken fat and vegetable shortening is more saturated than vegetable oil. A high intake of saturated fat increases your cholesterol level.

To protect your heart and blood vessels, you should reduce your overall fat intake—a measure that is more important than eating less cholesterol. About 30% of our calories should come from fats. Currently, most people in the UK get about 40% of their calories from fat. Another protective measure involves replacing some of the saturated fats you now consume with polyunsaturated fats found in vegetable oils and fish. Saturated fats raise cholesterol levels in the blood. Although it was once believed that monounsaturated fats had no effect on blood cholesterol levels, recent research studies suggest that a diet high in monounsaturated fatty acids is effective in reducing LDL levels while keeping HDL levels the same. Nevertheless, reducing overall fat intake is more important.

Changing my diet to protect my heart

Foods high in saturated fat to avoid include egg yolk, prawns, beef liver, beef, pork or lamb, veal, butter, whole milk, full fat and cream cheeses. Select lean cuts of meat and trim off any fat before cooking. Grilling food rather than frying will help to reduce the amount of fat present.

Foods containing lower levels of saturated fat include fish, poultry, dried beans and peas. Vegetables and fruits are beneficial. Poly-unsaturated margarine skimmed milk and low fat cottage cheeses, are good alternatives to high fat dairy products. Instead of sour cream use low-fat yogurt.

Some foods protect your heart

Oil rich fish (mackerel, sardines, pilchards, salmon, trout, kippers, herring) make platelets less likely to stick together. Platelets clumping together to form a clot in a narrow blood vessel may be one of the first things that happens when you develop a heart attack or stroke. Try to eat two portions of these each week.

Anti-oxidant vitamins (beta-carotene, and vitamins C and E) may also protect your heart by preventing unsaturated fats being converted to saturated fats in the body. There is good evidence that natural sources of these may reduce your chance of heart disease; these include fruits, vegetables and wholegrain cereals. Mediterranean style diets that contain plenty of fresh vegetables help protect against heart disease.

Soluble fibre, such as found in beans, peas and lentils, oatmeal and porridge oats, fruits and vegetables also has a small, but favourable, effect on cholesterol.

Selenium is an element that is found in trace amounts in your body. It has a vital role in protecting your body tissues from damage and in areas where selenium intake is low there are higher levels of heart disease. Brazil nuts are the richest natural source of selenium, so treat yourself to these on a regular basis.

Serve smaller portion sizes

This will help in two ways. Firstly the overall level of fat intake will be reduced and secondly, you will be better able to maintain your ideal weight, reducing further your risk of heart disease. Your body turns excess calories into fat that it saves up for the future. Using smaller dinner plates makes it easier to stick to smaller portions.

What level of cholesterol is safe?

We know that the relationship between cholesterol and heart disease is continuous. In other words, the higher your cholesterol, the higher your risk of heart disease; if you lower your level, your risk of heart disease drops, whether you start from a high or a low initial cholesterol level. There is no level that can be called safe, although at lower levels of cholesterol, the risk to your heart is small.

Cholesterol lowering drugs

There have been several large scale studies of cholesterol lowering drugs that have helped us determine at what level of cholesterol we should offer treatment. This varies depending on your other risk factors for heart and blood vessel disease. Once you start treatment you are likely to stay on it long term, so it is always worth trying to reduce your cholesterol using diet and exercise before committing yourself to drug therapy. Usually, we would give you a 3 month period in which to reduce cholesterol this way before suggesting treatment might be necessary.

If your cholesterol does not come down with dietary control and exercise we would look carefully at your overall risk of heart disease and stroke to decide whether drug treatment is necessary. These levels may change in the future as we learn more about the benefit of these drugs and their cost-effectiveness.

For women who are past the menopause (their last ever period) an alternative to cholesterol lowering drugs that might be considered is hormone replacement therapy. One of the female hormones (oestrogen) protects against heart disease. After the menopause women no longer produce natural oestrogens and this increases the risk of heart and blood vessel disease. Replacement hormones protect the heart.

Other risk factors for heart disease

As we have seen, consumption of high levels of saturated fat leads to high blood cholesterol and, in turn, to an increased risk of heart disease and stroke.

Whilst diet plays a part in controlling HDL and LDL levels, exercise will increase "good" cholesterol levels if the exercise is taken regularly. We would recommend a minimum of 20 minutes of exercise on alternate days.

Other factors that have been strongly implicated in heart disease are smoking, high blood pressure, obesity, and diabetes. The more risk factors you have the more careful you need to be to keep your cholesterol low. Reducing your other risk factors by, for example, stopping smoking, is most important. Reducing your cholesterol level without other lifestyle modifications still leaves you at risk, albeit reduced.

Stop smoking

Because cholesterol, smoking, blood pressure, obesity, and lack of exercise are all independent risk factors for heart disease you would be well advised to pay attention to all of these. The most important is stopping smoking.

Cardiovascular risk screening

If you have not had your cholesterol measured within the last 5 years, our practice nurse would be happy to take a blood sample for this. She will also be able to weigh you to calculate your Body Mass Index (a measure of obesity) and will check your blood pressure. If you need help to give up smoking then feel free to ask your doctor for advice.