‘Good Cholesterol’ Theory Challenged

A great deal of research has previously suggested that higher levels of “good” HDL cholesterol reduce your risk coronary heart disease, while higher levels of “bad” LDL cholesterol increase your risk of a heart attack. However, it has been hard to tell whether HDL cholesterol directly reduces coronary heart disease risk as other medical, biological or lifestyle factors could be involved. To get round this, researchers conducted a complex study to identify genes that raise levels of HDL cholesterol, then looked at whether carrying these genes influenced heart disease risk.

Researchers first identified genetic variants associated with high HDL levels and tested for them in several thousand people, including some who had had a heart attack. They found that carrying these “HDL cholesterol genes” had no effect on the risk of a heart attack. From this, the researchers concluded that there is no direct relationship between HDL cholesterol and coronary heart disease and, therefore, that other factors must be involved.

This complex study challenges the commonly held belief that having higher HDL cholesterol will reduce heart attack risk. However, as it only looked at a particular set of genetic variations, it cannot provide the whole answer and tell us whether HDL cholesterol does or does not affect coronary heart disease, and how this effect might come about. An important question is whether things that increase HDL cholesterol levels during our lifetime (i.e. after our genetics are determined), such as exercise and certain medications, can then improve our heart disease risk.

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