What it is
Regulatory status: dietary supplement
Mechanism evidence: human
At a glance
What it is, why people use it, the evidence, and what to know before trying it.
Why people use it
- **Serum total testosterone** (especially in late-onset hypogonadism / ADAM / T < 300 ng/dL).
- **Free testosterone** (and SHBG), the background “free T” claim.
- **LH and FSH** (the background “LH” claim).
- **Libido, erectile function, and sexual well-being** (IIEF, SHQ, AMS sexual subscale).
- **Strength and body composition** (grip, dynamometry, lean/fat mass) as an ergogenic.
- **Stress, mood, and cortisol**.
- **Spermatogenesis / male fertility** (semen volume, concentration, motility, morphology, spontaneous pregnancy).
- **Safety as a “natural TRT alternative”** (liver, kidney, PSA, T:E doping ratio) — listed here as a claim, tested in section 7.
Evidence at a glance
Standardized *Eurycoma longifolia* **water extract** (Physta / LJ100-type, ~0.8–1.5% eurycomanone) has **moderate** evidence that it can raise **serum total testosterone by a small absolute amount** in **older or hypogonadal men** over 1–6 months (Leisegang 2022 meta-analysis SMD 1.35, driven by that subgroup; Chinnappan 2021: +16 to +25 ng/dL vs a falling placebo). That is **not** TRT, and it is **not** shown in eugonadal or exercise-trained adults (Ismail 2012; Antonio 2024; Chen 2019). **Free testosterone** is a weaker, often within-group-only finding; **SHBG does not reliably fall**. **LH/FSH: unsupported in humans** — the one RCT that measured them was null (Chan 2021). Libido/AMS/IIEF signals exist but sit on industry RCTs with ceiling effects. Strength and body composition are **unsupported** at the background **400 mg** dose in trained people (Antonio 2024 null). Fertility data are open-label with 79% dropout. Short-term labs look clean; **EFSA 2021 refused novel-food safety**, product **heavy-metal and PDE5 adulteration are documented**, and one possible DILI case exists.