It is been believed that the more good cholesterol -- or HDL -- you have, the lower your risk for a heart disease.
But a new study challenges the theory, saying raising HDL levels may not make a difference at all.
Researchers found that people who inherit genes that naturally give them higher HDL levels throughout life have no less heart disease than those who inherit genes with lower levels.
Other researchers call the findings disturbing and say more studies need to be done.
The study is published in the online edition of The Lancet.