Crux of What Should Your Cholesterol Be? by Seth Roberts:

A 2011 study from Norway, based on 500,000 person-years of observation, found [that] the lowest levels of total cholesterol (below 5.0 mmol/L) were associated with the most death. For men, the best level was intermediate — what the Mayo Clinic calls “borderline high”. For women, the safest levels were the highest.”