Family doctor

Overview

•   Triglycerides - fatty acids in the bloodstream - are produced by the body and present in food.
• Recent research shows elevated levels of triglycerides can indicate a higher of risk of coronary heart disease (CHD), especially when combined with high cholesterol levels or in certain groups. High levels may also indicate diabetes and increase the risk of pancreatitis.
• Diet, alcohol intake and exercise levels have an effect on triglyceride levels.
• Testing triglyceride levels may provide information to predict risk of CHD, diabetes or bile duct blockages.
• Triglyceride tests involve a blood test following a period of no food of alcohol.
• Treatment and prevention may include changes to diet, reducing alcohol intake and increasing exercise. Some people will not respond to this and have drugs prescribed.

What are triglycerides?

Triglycerides are a type of fatty acid, or lipoprotein. A triglyceride molecule consists of three molecules of fatty acid combined with a molecule of the alcohol glycerol. Triglycerides come from food as well as being produced by the body. Triglycerides levels may be routinely tested in those patients at risk of coronary heart disease or with high cholesterol.

Who are at risk from elevated triglyceride levels?

There has been much debate in medical circles about the effect triglyceride levels have on the risk of coronary heart disease (CHD). More recent research indicates high triglyceride levels do increase risk of CHD and are a particularly good indicator of risk of CHD for:

•   type 2 diabetes patients
• women
• younger people
• people with low levels of LDL and HDL cholesterol measures.

Triglycerides are elevated in people who are overweight and in those who eat too much refined sugar, alcohol and fat.

Why are high levels of triglycerides a risk factor?

The reasons why high levels of triglycerides increase the risk of CHD is not completely understood. The most recent evidence suggests the remnants left from the breakdown of triglyceride rich lipoproteins in the blood may speed up plaque build up on arteries (atherogenesis). It seems these particles floating in the blood are particularly dangerous to patients with high levels of triglycerides and cholesterol.

High triglyceride levels increase the risk of thrombosis - clotting, which can lead to myocardial infarction - heart attack.

A combination of diet and high triglyceride levels can be a risk factor. A fatty meal leaves remnant lipoproteins in the blood, and those with high levels of triglycerides do not clear these fragments as quick as other people. This delay has been shown to increase the risk of CHD.

For those suffering from metabolic syndrome, also known as syndrome X, high triglyceride levels seem to be an important factor. This group suffer from abdominal obesity, have a glucose intolerance and high insulin levels. Some of these patients go on to develop type 2 diabetes. These patients are at high risk of CHD, usually due to atherogenic dyslipidaemia - build up of plaque from high levels of triglycerides and cholesterol.

High triglyceride levels commonly occur in younger people suffering inherited elevated cholesterol levels. This inherited disorder results in overproduction of cholesterol and triglycerides by the body. Thus, early testing for triglycerides may show up this condition and allow early treatment to reduce the risk of CHD.

High levels of triglycerides and intermediate density lipoproteins (IDL) advance CHD. IDL is a remnant of very low density lipoprotein metabolism, and high levels of IDL are linked to lesion progression in sufferers of CHD. Coronary lesions continue to progress despite the use of lipid lowering drugs in between 20-60% of patients, leaving them at risk. IDL levels remain high in those with progressing lesions, whereas those with lesions not progressing have lower or decreasing levels of IDL. Thus, therapies that can decrease IDL may delay development of lesions.

Various types of triglyceride-rich lipoproteins can cause risks. For instance chylomicrons and VLDL(very low density lipoprotein) particles are triglyceride too large to penetrate the blood walls, however they can cause inflammation of the pancreas (pancreatitis).

Why would a doctor test for triglycerides levels?

Consistently high levels of triglycerides may indicate a risk of CHD. It may also indicate a possible diabetes development.

Measuring the levels of specific triglycerides and LDL may help assess a patient's risk of CHD.

Mild to moderate triglyceride levels may be linked to alcohol abuse, obstruction of bile ducts and diabetes symptoms. Extremely high levels can cause inflammation of the pancreas.

When are levels considered high?

High levels of triglycerides are usually those above 2.3 mmol/L. Recent studies show this cut off point for deciding on treatment may lead to exclusion of some patients at risk from CHD.

Extremely high triglyceride levels are those greater than 500 mmol/L.

How are triglycerides tested?

The test is a simple blood test. A normal level relates to the age and sex of the person tested.

Triglyceride testing usually involves taking a blood sample, following a period of fasting. The result is known as the fasting glyceride concentration. Before being tested for triglycerides no food is eaten for at least 12 hours and no alcohol taken for at least 24 hours.

The fasting test does not take into account the effect of triglycerides circulating in the blood following a meal, which, as discussed above, may increase the risk of CHD.

What treatments are used to lower triglycerides?

Mild to moderately raised levels of triglycerides are treated by weight loss, restricting alcohol intake and increasing exercise. Markedly high levels of triglycerides should be treated aggressively with low fat diets and, if needed, medications.

The use of drugs may be recommended when there are high levels of both triglycerides and cholesterol, if the patient has low high density lipoproteins (LDL) or the overall risk of CHD is high. The most commonly used drugs are fibrates, however in some cases this drug alone increases LDL so a combination of drugs may be required.

Nicotinic acid is known to reduce triglycerides, cholesterol and CHD risk however side effects usually make this treatment unpopular.

How can it be prevented?

Controlling fat and alcohol intake can influence the levels of triglycerides in the blood. However, people with an inherited condition where triglycerides are overproduced can not influence levels by diet alone.

Monitoring triglyceride levels by testing and seeking medical advice on individual risk of CHD or diabetes is a good idea, to identify any conditions arising from high levels.