The problem was that D-Aspartic acid taken alone could deplete your testosterone precursors. Just to be on the safe side, I thought I should have testosterone precursors in reserve. The three primary precursors of testosterone are progesterone, pregnenolone and DHEA. These three precursors were also listed in a scientific article as a means of reducing cholesterol if you returned them (along with testosterone) to “youthful” levels. Since my cholesterol was on the high side, it made sense to try all of them, plus I had literature supporting the idea of taking them.