You're probably aware that high density lipoprotein (HDL) also known as good cholesterol is popular in lowering the risk of heart disease. I believed that as well until I read the recent study conducted at Cambridge University.
According to the study rare mutation in genes known as SCARB1 is a kind if mutation in which a person have high level of HDL. But it also suggests that such person is 80% at risk of acquiring heart disease.
Read more on this topic here.