QUESTIONS & ANSWERS: GLOSSARY

Lipids HDL, LDL, LP(a) / cholesterol / fats and oils

Solid lipids are called fat, eg butter; liquid lipids are called oils, eg olive oil. Lipid is an essential component of the body and of the diet. All cell membranes are made of lipid; the specialised cells of the brain and nervous system have more lipid. Fat-free and low-fat diets are not advised, especially to children with developing brains.

One theory of atherosclerosis proposes that coronary heart disease (CHD) is due to raised blood levels of the lipid called cholesterol. However, many people with normal cholesterol have heart attacks due to CHD. Indices of thrombosis, and inflammation correlate better with the occurrence of CHD than blood cholesterol. Part of cholesterol is called "high density" and protects people against CHD while part is called "low density" and carries a predisposition to CHD. Lipoprotein(a) (Lp(a)) carries a strong predisposition to CHD but may well act because it directly stimulates thrombosis.

There is also a theory that certain types of lipid in the diet, called "saturated fat", occurring in meat and dairy products, carries a predisposition to CHD, whereas "unsaturated fat" from fish and vegetables carries a protection against CHD. This is based on the apparent partial immunity to CHD enjoyed by Mediterranean people. Eating a Mediterranean diet is therefore a positive advice about what to eat, but the benefits are not proven by strict scientific method as have the benefits of statins. Nor are there any proper comparisons of outcome between, for instance, margarine and butter.

There are some families with inherited (genetically determined) high blood lipids. Depending on the type of lipid, these families may have much increased risk of CHD and others not.

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