Keeping low-density lipoprotein or LDL (known as bad cholesterol) under check is good for your heart. But raising levels of good cholesterol or HDL - as often suggested by medical experts - may not have any impact on your heart disease risk, a new study says.

The study published on Wednesday in The Lancet medical journal challenges the established notion that raising a person's HDL necessarily lowers the risk of a heart attack. It says there is no direct relationship between higher levels of HDL and a lower risk of heart attack.

This implies that it is best to focus on lowering the levels of LDL in order to tackle heart disease. "Ways of raising HDL cholesterol might not reduce risk of myocardial infarction," said Dr. Sekar Kathiresan from Massachusetts General Hospital, who led the study.

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