Lp(a) is lowered by L-carnitine, Vit D,and Niacin (slo). I also think it is lowered by Vit K (MK-7). The purpose of the Vit C is not to lower the level of Lp(a) but to re-purpose it into a more harmless particle.
I suggest you read this rather extensive article about the purpose of Lp(a) and how Vit. C interacts with it: http://knowledgeofhealth.com/something- ... rol-world/