Tongkat Ali & Fadogia Agrestis: Huberman's T Stack

When Dr. Andrew Huberman discussed his testosterone optimization protocol on the Huberman Lab podcast, two herbal supplements became overnight sensations: Tongkat Ali (Eurycoma longifolia) and Fadogia Agrestis. Together, they form what many now call "Huberman's testosterone stack" — a natural approach to supporting healthy testosterone levels without exogenous hormones. Here is a complete evidence-based breakdown of both compounds.

Why Natural Testosterone Support Matters

Testosterone levels in men have declined approximately 1% per year since the 1980s, according to a 2007 study in the Journal of Clinical Endocrinology & Metabolism. This generational decline cannot be explained by aging alone and is likely driven by environmental endocrine disruptors, obesity, poor sleep, and chronic stress.

Symptoms of suboptimal testosterone include low energy, reduced libido, brain fog, loss of muscle mass, increased body fat, poor recovery, and mood disturbances. While TRT (testosterone replacement therapy) is appropriate for clinically low levels, many men prefer to optimize their natural production first. That is where Tongkat Ali and Fadogia Agrestis come in.

Tongkat Ali (Eurycoma longifolia): The Evidence

Tongkat Ali is a medicinal plant from Southeast Asia with a long history of traditional use for vitality and libido. Modern research supports several mechanisms of action:

How Tongkat Ali Works

• Reduces SHBG (Sex Hormone-Binding Globulin): SHBG binds to testosterone, making it biologically unavailable. By lowering SHBG, Tongkat Ali increases free testosterone — the fraction that actually exerts biological effects.
• Cortisol reduction: A 2013 study in the Journal of the International Society of Sports Nutrition found Tongkat Ali improved testosterone-to-cortisol ratio by 36% in stressed adults. Cortisol and testosterone have an inverse relationship.
• Potential LH stimulation: Some evidence suggests Tongkat Ali supports hypothalamic-pituitary signaling, promoting natural luteinizing hormone (LH) release to stimulate Leydig cell testosterone production.

Clinical Evidence for Tongkat Ali

• A 2021 systematic review and meta-analysis of 9 RCTs found Tongkat Ali significantly improved total testosterone levels with an overall moderate effect size.
• A 2012 study showed 200 mg/day of standardized Tongkat Ali extract increased testosterone by 37% in men aged 30–55 over 4 weeks.
• Improvements in sperm concentration, motility, and morphology have been documented in subfertile men.

Huberman's Tongkat Ali Dosage

Huberman recommends 400 mg/day of standardized Tongkat Ali extract (standardized to at least 2% eurycomanone, the primary bioactive compound). He takes it in the morning, as it can have a mild energizing effect.

Fadogia Agrestis: The Evidence

Fadogia Agrestis is a Nigerian shrub that has gained attention for its potential to increase testosterone through a different mechanism than Tongkat Ali. Huberman popularized it as a complement to Tongkat Ali, creating a two-pronged approach.

How Fadogia Agrestis Works

• Leydig cell stimulation: Animal research suggests Fadogia acts directly on Leydig cells in the testes to increase testosterone synthesis, possibly by mimicking luteinizing hormone signaling.
• Complementary to Tongkat Ali: While Tongkat Ali primarily works by reducing SHBG and cortisol, Fadogia may increase total testosterone production at the source — making the combination theoretically synergistic.

Important Caveats About Fadogia Agrestis

Transparency requires noting that the evidence for Fadogia is substantially weaker than for Tongkat Ali:

• No human clinical trials exist. All data comes from rodent studies, which do not always translate to humans.
• The primary 2005 animal study showed dose-dependent testosterone increases in rats, but also noted testicular histological changes at higher doses that raised safety concerns.
• Product quality varies enormously. Third-party testing has revealed many Fadogia supplements contain little to no active compound.
• Huberman himself has acknowledged these limitations and recommends cycling.

Huberman's Fadogia Agrestis Dosage

Huberman recommends 425–600 mg/day of Fadogia Agrestis, cycled 8 weeks on, 2–4 weeks off as a precautionary measure given the limited safety data.

Huberman's Complete Testosterone Optimization Stack

Beyond Tongkat Ali and Fadogia, Huberman recommends a comprehensive approach:

1. Tongkat Ali — 400 mg/day (daily, no cycling needed)
2. Fadogia Agrestis — 425–600 mg/day (8 weeks on, 2–4 weeks off)
3. Zinc — 30–50 mg/day (essential for testosterone synthesis enzyme activity)
4. Boron — 6–12 mg/day (reduces SHBG and increases free testosterone by ~25% in some studies)
5. Vitamin D3 — 5,000 IU/day (deficiency strongly correlated with low testosterone)
6. Ashwagandha KSM-66 — 600 mg/day (reduces cortisol by 27%, indirectly supporting testosterone; a 2019 study showed it increased testosterone by 15% in exercising men)

Lifestyle Foundations Huberman Emphasizes

Huberman is clear that supplements are only one pillar. He equally emphasizes:

• Resistance training: Heavy compound lifts (squats, deadlifts) are the most potent natural testosterone stimulus
• Sleep: 7–9 hours of quality sleep. Testosterone is primarily produced during REM sleep
• Morning sunlight: 10–15 minutes of sunlight exposure within the first hour of waking regulates circadian hormones
• Cold exposure: Brief cold exposure may support dopamine and testosterone signaling
• Minimize alcohol and processed food

Blood Work to Monitor

Before starting and 6–8 weeks into any testosterone protocol, test:

• Total testosterone
• Free testosterone
• SHBG
• Estradiol (E2)
• LH and FSH
• Prolactin
• Complete metabolic panel (liver/kidney function)

Services like InsideTracker make comprehensive hormone testing accessible without a doctor's order.

Frequently Asked Questions

Can women take Tongkat Ali?

Yes. At 100–200 mg/day, Tongkat Ali has been shown to improve energy, mood, and libido in women without causing virilization. Women produce and need testosterone too, just at lower levels.

Does Tongkat Ali increase estrogen?

No. Tongkat Ali does not aromatize and may actually help balance the testosterone-to-estrogen ratio. If you are concerned about estrogen conversion, DIM (Diindolylmethane) can be added to support healthy estrogen metabolism.

Why does Fadogia Agrestis need to be cycled?

The animal study data showed testicular histological changes at high doses, raising theoretical safety concerns. Until human clinical trials establish a clear safety profile, cycling is a precautionary measure recommended by Huberman and most practitioners.

How long before I notice results from this stack?

Most men report noticeable improvements in energy, libido, and recovery within 2–4 weeks. Blood work changes typically become apparent at the 6–8 week mark.

Is this stack a replacement for TRT?

No. If your total testosterone is below 300 ng/dL with symptoms, consult an endocrinologist about TRT. This stack is designed for men with borderline or suboptimal levels (300–500 ng/dL) who want to optimize naturally before considering medical intervention.