What is cholesterol, and should I have my level checked?

Cholesterol is a white fatty substance (a lipid) that occurs naturally in people and animals, but not in plants. You need a little cholesterol to make cell membranes, hormones, bile salts and vitamin D. But you don’t need to eat any cholesterol: your body makes its own supply.

Having a raised blood cholesterol level increases your risk of heart disease. Excess cholesterol in the blood can end up in fatty deposits on the lining of arteries.

But the cholesterol in the blood isn’t all harmful.

The dangerous stuff that clogs up arteries is called LDL-cholesterol and you want your level of that to be as low as possible.

HDL-cholesterol, on the other hand, is protective; you want your HDL-cholesterol level to be as high as possible.

If your doctor arranges a blood test to check your cholesterol, it will normally be a ‘fasting lipid profile’. As well as the total cholesterol level, this will tell you the levels of LDL-cholesterol, HDL-cholesterol and triglycerides. (A screening test can be done without fasting; this only tells you the total cholesterol level which can be misleading if it hides a high or low level of HDL.)

The concentration of triglycerides (fats) in the blood goes up shortly after eating, which is why the lipid profile has to be done on a fasting sample. If you break the fast, the triglyceride reading is meaningless and that throws out calculation of LDL-cholesterol.

Quite rightly, a lot of attention is paid to reducing LDL-cholesterol. But having raised fasting triglycerides increases risk too. In particular, the combination of low HDL with raised triglycerides is bad news; this is commonly seen in diabetes and in the metabolic syndrome.

The only way to find out about your lipid profile is to have it measured. You can’t assume your cholesterol level is OK because you eat a ‘good diet’ or because you’re not overweight.

About 1 in 500 people have the serious condition of familial hypercholesterolaemia (FH) in which the cholesterol level is genetically programmed to be very high indeed. Simple treatment is life-saving.

Average cholesterol levels in the developed world are too high and the chances are that your lipid profile has a lot of room for improvement.

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