Niacin has been more well known for its positive effects on HDL.  Its effects on LDL have been more modest.  Such modesty, however, deserves special attention in that it is indeed associated with an increase in LDL particle size and a shift from small LDL to the less atherogenic, large LDL subclasses.  Therefore, we are looking at niacin from a standpoint of quality of LDL that it promotes, not just the quantity that it would reduce it by.   This is a crucial point.

Note that a 2006 study in the American Journal of Cardiology showed that 3 months of ER niacin use in subjects w/ CAD increased large particle LDL  by 82% and decreased small particle LDL by 12%.    

Dr. K