L-Aspartic Acid, particularly in its D-aspartic acid (DAA) form, has been studied for its potential role in supporting the male reproductive system, especially regarding testosterone production and fertility. Scientific research indicates that DAA is involved in the regulation of the hypothalamic-pituitary-gonadal axis, which plays a crucial role in testosterone synthesis. Several human studies have explored DAA supplementation in men, with mixed results. Some short-term studies (e.g., 12 days) have reported modest increases in testosterone levels among healthy men and those with low testosterone. However, longer-term studies (e.g., 28 days or more) have not consistently shown sustained or significant benefits in testosterone enhancement or fertility parameters.

The evidence supporting the use of L-aspartic acid (or more specifically, D-aspartic acid) for male reproductive health is therefore considered moderate. Its use is justified by scientific studies, although the effects appear to be modest, short-term, and variable among individuals. There is not strong or consistent evidence to support its routine use for male reproductive health, but the mechanism by which DAA may influence hormone levels is biologically plausible and supported by some clinical findings. Overall, while there is scientific rationale and some positive studies, the strength and reproducibility of the evidence warrant a mid-range score.