I take Ginko and Ginseng daily for a few months now with Cranberry tablets [Seamen/urine system], Cod Liver oil [Joints], Multi vitamins and minerals, and Niacin is in that, and it helps out as well, very much so.
Also I take Zinc which is great for the Prostate and Ejac' system.
I also take the odd Testostarone booster.
I have noticed that over my time using these things that my erections are better, freq' and that my cock fills up more volume and gets its space filled more, so the flaccid stretch becomes Now and again the Erect BP.
Safer than taking Viagra, BUT that is a quicker response indeed, it takes months of reguler use of these herbs to get the Viagra effect.