Supplementing with D-aspartic acid, a naturally occurring amino acid, can lead to significant increases in testosterone production. In one study, published in the journal Reproductive Biology and Endocrinology, subjects who supplemented with 3 grams
for 12 days increased their T levels by over 40%.



E. Topo et al., Reprod Biol Endocrinol., 7: 120, 2009.