We've long been told that HDL cholesterol reduces the risk of heart disease, strokes and circulatory problems while LDL cholesterol increases the risk. In general, this seems to be true, but worrying research from the Cleveland Clinic in the United States indicates that under certain circumstances HDL cholesterol can become harmful.
LDL cholesterol is named from the fact that low density lipoproteins carry the cholesterol through the blood. The route is from the liver to the cells of the body, which require cholesterol in order to function. Excess LDL cholesterol builds up in the lining of arteries and along with other substances forms a deposit called plaque. Plaque can block blood flow and trigger the formation of blood clots. On the other hand, HDL cholesterol carries cholesterol away from the arteries to the liver to be processed, thereby reducing the likelihood that plaque will form.
Health experts encourage us to follow a healthy diet, exercise regularly and avoid smoking in order to develop a high HDL cholesterol to low LDL cholesterol ratio. The Cleveland Clinic researchers are careful to point out they don't recommend any changes to this strategy. However, they also say that our present understanding of HDL cholesterol is inadequate.
Dr. Stanley Hazen, a spokesperson for the researchers, says that sometimes when HDL cholesterol enters the arterial lining it's altered. The altered molecule behaves differently from the HDL cholesterol that is travelling in the blood. Small amounts of the altered HDL cholesterol enter the bloodstream and can be detected. In a study of 627 patients performed by the clinic, the blood level of the altered HDL cholesterol could be used to predict the risk of heart disease.
Researchers are hoping to find new tests for the abnormal HDL cholesterol and medications to treat it. It would be great if they could also discover exactly why and how HDL cholesterol is changed in the arterial lining.