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* Topo et al., 2009, Reprod. Biol. Endocrinol. 200, 7:120. Study lasted 12 days and showed an average increase of 42% in total testosterone levels.
The effects of D-Aspartic Acid on free testosterone were not investigated. Although only free testosterone provides the muscle enhancement and other benefits associated with testosterone, many experts agree that an increase in total testosterone is accompanied by a similar increase in free testosterone. Swerdloff et al, 2000, J Clin Endocrinol Metabolism 85: 4500.