CHOLESTEROL
Cholesterol is a type
of fat (lipid) made by the body. It is essential for good health and is found in every cell in the body. However, a
high cholesterol level in the blood is associated with an increased risk of heart disease and stroke. Seven out of 10 people
over 45 have high cholesterol.
The main risk associated
with high cholesterol is cardiovascular disease (CVD). This includes diseases of the heart and blood vessels. High cholesterol
causes blood vessels to become narrowed with fatty deposits called plaques. This can result in heart attacks, strokes and
blood vessel problems
Types of cholesterol
Cholesterol is transported
around the body in the blood attached to a protein. This combination of fat and protein is called a lipoprotein. Lipoproteins
can be high density (HDL), low density (LDL) or very low density (VLDL), depending on how much protein there is in relation
to fat.
LDL (low density lipoprotein)
Most
of the body's cholesterol is transported as LDL. This is made up of mostly fat and a small amount of protein. Too much LDL
in the blood can cause cholesterol deposits to build up in the arteries, making it harder for the blood to flow through these
blood vessels. High levels of LDL in the blood are associated with an increased risk of CVD. So LDL is sometimes referred
to as " bad cholesterol".
HDL (high density
lipoprotein)
A
small amount of cholesterol is transported as HDL, which is mostly made up of protein and a small amount of fat. HDL actually
helps prevent cholesterol deposits building up in the arteries. Having low levels of HDL (compared with LDL) in the blood
is associated with an increased risk of CVD. So HDL is sometimes referred to as "good cholesterol". Women tend to have higher
levels of HDL cholesterol than men.
If the total cholesterol (TC) level is too high,
this is one risk factor for health problems. However, it's important to consider the relative amounts of HDL and LDL. This
is often referred to as the TC: HDL ratio. A high level of HDL and a low level of LDL (so a low TC: HDL ratio) is desirable.
Triglycerides
Triglycerides are a different
type of fat, which mostly come from fats in your food. Energy that is eaten and not used immediately is converted into triglycerides
and transported to fat cells for storage. This is an important source of stored energy. Although most triglycerides are stored
in fat tissue, low levels are also found in the blood. They are carried in the blood as very low density lipoproteins (VLDL).
A raised level of blood triglycerides together
with high LDL can increase the risk of heart disease, particularly in people with diabetes.
What causes high cholesterol?
There are several factors that may contribute
to high blood cholesterol:
- A diet that's high in saturated fat and, less so, high in cholesterol (see How
diet affects cholesterol below).
- Lack of exercise may increase LDL cholesterol and decrease HDL cholesterol.
- Family history - people are at a higher risk of high cholesterol if they have a direct male relative aged under 55
or a female relative aged under 65 affected by heart disease.
- Being overweight, which may increase LDL cholesterol and decrease HDL cholesterol.
- Age and sex - cholesterol generally rises slightly with increasing age, and men are more likely to be affected than
women.
- Drinking more than the recommended amount of alcohol (i.e. more than three to four units per day for men and two to
three units per day for women)
Rarely, high cholesterol can be caused by a condition
that runs in the family called a lipid disorder (familial hypercholesterolaemia). About one in 500 people have this condition.
Other health conditions such as poorly controlled
diabetes, certain kidney and liver diseases and an underactive thyroid gland may also cause cholesterol levels to rise. Some
medicines such as beta-blockers, steroids or thiazides (a type of diuretic) may also affect blood lipid levels.
How diet affects blood cholesterol
Only a small amount of cholesterol comes directly
from your diet - the majority is produced by your liver. However, if your diet is high in saturated fats and cholesterol this
can cause your liver to produce more LDL ("bad") cholesterol. The amount that diet influences cholesterol levels varies from
person to person.
Measuring cholesterol
The amount of cholesterol in your blood is measured
in units called millimoles per litre of blood, usually shortened to "mmol/litre" or "mmol/l". America uses the units milligrams
per decilitre of blood: "mg/dl" instead. Current UK guidelines state that it is desirable to have a total cholesterol level
under 5mmol/l, and an LDL level under 3mmol/l.
In order to estimate your risk of getting CVD,
the best indicator of risk is your TC: HDL ratio. A lower ratio is desirable, because this indicates that you have high levels
of HDL.
Measuring cholesterol involves a simple blood
test. Usually you will be asked not to eat for 12 hours before the test so that your food is completely digested and doesn't
affect the test. A blood sample may be taken either by using a needle and a syringe or by using a finger prick.
Home-testing kits for cholesterol may not be
very accurate. Also, cholesterol is just one of the risk factors for heart disease. It should ideally be measured under medical
supervision so that other important issues, such as blood pressure, age and whether or not you smoke, are taken into account.
Who should have a cholesterol test?
Anyone who has any cardiovascular disease, such
as coronary heart disease, peripheral vascular disease (disease in the blood vessels that supply the limbs) or stroke, should
have their cholesterol measured by a doctor.
Anyone, even children, with a family history
of familial hypercholesterolaemia should have their cholesterol measured.
Anyone aged 35 or over should consider having
their cholesterol measured if they have one or more of the following risk factors for CVD: family history of early heart disease,
diabetes, high blood pressure, or if they smoke.
Diagnosis
Having a high cholesterol level does not cause
symptoms. Most people find out they have high cholesterol when they have their blood cholesterol measured as part of a medical
check-up. Alternatively, it may be identified after other health problems, such as heart disease, have been diagnosed.
Treatment
The main aim of lowering cholesterol is to reduce
the risk of heart disease. The type of treatment depends on the overall risk of heart disease.
There are two ways to help lower high cholesterol.
The first is with simple lifestyle changes including changing diet, managing weight and increasing exercise. The second is
to combine lifestyle changes with cholesterol-lowering medicines.
Diet
Healthy eating can reduce cholesterol. Your diet
should be low in saturated fats in particular, and low in fat overall. Biscuits, cakes, pastries, red meat, hard cheese, butter
and foods containing coconut or palm oil all tend to be high in saturated fats, so cut down on these foods.
Large amounts of cholesterol are found in a few
foods, including eggs and offal such as liver and kidneys. Although dietary cholesterol does not usually contribute much to
blood cholesterol, it is still advisable to limit these foods to three servings a week if you have high cholesterol.
It's also important to eat plenty of fiber, especially
soluble fiber, which is thought to lower cholesterol. It's found in fruits and vegetables, beans and oats.
Medicines
Cholesterol-lowering medicines are considered
for people who already have CVD, or are at high risk of getting it because they have other risk factors.
The main group of medicines for lowering cholesterol
is statins. Examples include simvastatin (Zocor) and atorvastatin (Lipitor). They work by reducing the production of cholesterol
in the liver. Occasionally these drugs have side effects such as indigestion and muscle pains.
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