70 (1.8 mmole/l) seems low alright - mine is just below 4 (150 mg/dl). However, my HDL is 1.6 and I'm 65 with no health complications and none in my family either. So, my doctor is content.
Niacin can reduce LDL, but at the doses required I'm not at all sure it's any safer than statins. Drinking lots of alcohol not only reduces LDL but also dissolves out most fats lining arteries, but few recommend that!