Dr John Briffa has a good article which states in the introductory paragraph...
"I know that some doctors and scientists would have us believe that, where cholesterol is concerned, "lower is better", but I have real difficulty mustering any entheusiasm for this stance. And one major reason for this is the fact that low levels of cholesterol are associated with enhanced risk of death, perhaps most notably from increased risk of cancer."
Please read the complete article here.