Bring Back the Drive, Stamina & Confidence You Stopped Expecting to Feel

L-Arginine is a well-studied precursor to nitric oxide, the signaling molecule responsible for relaxing and widening blood vessels. A double-blind, placebo-controlled study published in BJU International found that high-dose oral L-arginine improved reported sexual function in a subset of men with organic erectile difficulty, particularly those with low baseline nitric oxide activity (Chen J, et al. BJU Int. 1999).

The complicating point: the effect wasn't universal in that trial — men with normal nitric oxide markers saw little benefit, suggesting L-arginine helps most when there's an underlying circulation gap to close, not as a blanket enhancer.

Source: Chen J, Wollman Y, Chernichovsky T, et al. BJU International. 1999.

A randomized, double-blind, placebo-controlled study in Andrologia found that daily Maca root supplementation improved self-reported sexual desire in healthy adult men over an 8-week period — notably, without any measurable change in serum testosterone levels (Gonzales GF, et al. Andrologia. 2002).

That last point matters: Maca's traditional reputation is often framed around "testosterone," but the clinical data points to a different, non-hormonal mechanism that researchers still don't fully understand.

Source: Gonzales GF, Córdova A, Vega K, et al. Andrologia. 2002.

We're not going to oversell this one. A widely cited review in the Journal of Ethnopharmacology examined the pro-sexual and androgen-enhancing claims made about Tribulus terrestris and concluded the human clinical evidence was inconsistent — some animal studies showed effects that simply didn't replicate reliably in human trials (Neychev VK, Mitev VI. J Ethnopharmacol. 2005).

We include it because it has a long history of traditional use and a reasonable safety profile, not because the clinical case is closed. If you're looking for the single strongest-evidence ingredient in this formula, it's L-Arginine or Horny Goat Weed's icariin content, not Tribulus.

Source: Neychev VK, Mitev VI. Journal of Ethnopharmacology. 2005.

Icariin, the primary active compound in Horny Goat Weed (Epimedium), has been studied for its role as a mild PDE5-pathway modulator — the same general mechanism class as leading prescription options, though far less potent and not a substitute for one. Laboratory research published in the Journal of Natural Medicines demonstrated icariin's effect on smooth muscle relaxation and blood flow markers (Dell'Agli M, et al. J Nat Med. 2010).

Most of the strongest icariin research remains in laboratory and animal models rather than large-scale human trials, which is a meaningful limitation worth being upfront about.

Source: Dell'Agli M, et al. Journal of Natural Medicines. 2010.

A randomized, double-blind, placebo-controlled study published in the American Journal of Men's Health examined ashwagandha root extract in aging, overweight men and found improvements in self-reported vitality and hormonal markers compared to placebo over an 8-week period (Lopresti AL, Drummond PD, Smith SJ. Am J Mens Health. 2019).

Ashwagandha's best-supported mechanism is its role as an adaptogen — helping the body manage everyday stress — which is a meaningfully different (and better-supported) claim than a direct performance enhancer.

Source: Lopresti AL, Drummond PD, Smith SJ. American Journal of Men's Health. 2019.

Both botanicals have a long history of traditional use in Brazilian herbal medicine for male vitality and confidence. The modern clinical research on both is thin — mostly small, older studies and ethnobotanical reviews rather than the kind of large, controlled trials we can point to for L-Arginine or Ashwagandha.

Dr. Reyes's review is direct on this point: we include them because of their long traditional-use history and favorable safety profile, not because we can point you to a large modern clinical trial. We'd rather say that plainly than dress up a thin evidence base.