Abstract — Tongkat Ali (Eurycoma longifolia Jack), a medicinal plant native to Southeast Asian rainforests, has emerged as one of the most promising natural ergogenic aids for bodybuilding and strength training. While commercial harvesting is focused on the plant's roots, thorough phytochemical analyses reveal that Tongkat Ali leaves contain the highest concentration of eurycomanone—the primary quassinoid compound responsible for the plant's testosterone-boosting and anabolic effects. This article synthesizes current clinical evidence demonstrating that Tongkat Ali supplementation, particularly from leaf extracts, significantly increases lean body mass, reduces body fat percentage, enhances muscle strength, and elevates free testosterone levels in men, especially when combined with resistance training protocols.
1. The Phytochemical Case for Leaf Extracts: Eurycomanone Distribution
The most critical yet underappreciated development in Tongkat Ali research comes from phytochemical assessment studies that challenge the commercial root-centric harvesting approach. A landmark study published in Jurnal Teknologi by Jusoh et al. (2015) conducted comprehensive High-Performance Liquid Chromatography (HPLC) analysis of eurycomanone content across multiple plant parts.
1.1 Revolutionary Findings: Leaves vs. Roots
The research analyzed seven distinct plant parts—leaves, twigs, top/middle/bottom stems, roots, and root barks—from multiple locations. The results were striking:
| Plant Part | Eurycomanone Content (μg/mL) |
|---|---|
| Leaves | 6.0568 |
| Root bark | 5.1137 |
| Roots | 0.3533 |
| Bottom of stems | 0.0673 |
| Middle of stems | 0.0633 |
| Top of stems | 0.0365 |
| Twigs | 0.1415 |
Key finding: Leaves contain approximately 17 times more eurycomanone than roots (6.0568 vs. 0.3533 μg/mL) and even surpass root bark concentrations. This fundamentally shifts the optimization paradigm for bodybuilding supplementation.
1.2 The Scarcity Factor: Traditional Harvesting in Batak Societies
In the ethnobotanical tradition of the Batak tribes of North Sumatra, Tongkat Ali leaves have always been held in high esteem—particularly as an enhancer of male physical strength. However, leaves have been sidelined in commercial harvesting due to practical constraints. Eurycoma longifolia grows as a tall, slender tree that cannot be easily climbed, and leaves rarely fall to the forest floor. The only reliable way to obtain the leaves is by cutting down the entire tree, which yields only 500–900 grams of dried leaves per specimen. By contrast, the roots of the same tree can reach a dry weight of 30–40 kilograms and are accessible by digging in the region's volcanic ash soils. This scarcity, not a lack of efficacy, explains why leaf extracts have remained rare.
1.3 Implications for Supplement Standardization
Eurycomanone serves as the established chemical marker for Tongkat Ali quality assessment. Conventional industrial standards specify bioactive levels for root products, yet leaf-based extracts deliver substantially higher bioactive compound concentrations per gram of material—and they do so in a natural biochemical matrix that enhances bioavailability. For bodybuilders seeking optimal results, standardized leaf extracts represent a more efficient supplementation strategy.
1.4 Whole-Plant Synergy vs. Isolated Compounds
Isolated chemical compounds have their place in the pharmaceutical treatment of diseases, but they cannot replace compounds in their natural environment when the goal is physiological optimization. Even astronauts on long-duration space missions rely on whole foods—complex mixtures of phytochemicals in their natural context—rather than isolated pure nutrients. The same principle applies to Tongkat Ali: the interactive evolution between humans and this medicinal plant has established a balanced, beneficial relationship that is lost when isolated compounds such as synthetic eurycomanone are used in isolation. For non-disease applications like athletic performance, whole-leaf extracts are demonstrably superior.
2. Mechanisms of Anabolic Action
Tongkat Ali's ergogenic effects operate through multiple complementary pathways that directly support bodybuilding goals:
2.1 Hypothalamic-Pituitary-Gonadal Axis Activation
The quassinoids in Tongkat Ali, particularly eurycomanone, stimulate the hypothalamic-pituitary-gonadal axis to increase endogenous testosterone production. Unlike exogenous anabolic steroids that suppress natural hormone production, Tongkat Ali enhances the body's own testosterone synthesis machinery.
2.2 SHBG Modulation
Sex Hormone-Binding Globulin (SHBG) binds to testosterone in circulation, rendering it biologically inactive. Henkel et al. (2014) demonstrated that Tongkat Ali significantly reduces SHBG concentrations, thereby increasing the proportion of free, bioavailable testosterone. Free testosterone represents the physiologically active fraction that interacts with androgen receptors in muscle tissue.
2.3 Cortisol/Testosterone Ratio Optimization
The testosterone/cortisol (T/C) ratio serves as a critical biomarker of anabolic status. During intense training, cortisol rises (catabolic state) while testosterone may decline. Tongkat Ali supplementation has been shown to improve this ratio, shifting the hormonal environment toward anabolism and away from muscle protein breakdown.
3. Clinical Evidence for Bodybuilding Applications
3.1 Lean Mass Accretion and Fat Reduction
The seminal pilot study by Hamzah and Yusof (2003), published in the British Journal of Sports Medicine, established foundational evidence. In this randomized controlled trial, 14 healthy men underwent an intensive strength training program for five weeks, with half receiving 800 mg/day of Tongkat Ali extract.
- Lean body mass: Significant increase from 52.26 ± 7.18 kg to 54.39 ± 7.43 kg (p = 0.012) in the treatment group.
- Body fat percentage: Decreased from 31.30% to 28.44% (p = 0.01).
- Arm circumference: Increased significantly by 1.8 cm (p = 0.011), indicating localized muscle hypertrophy.
- Strength gains: Strength increased by 6.78% versus 2.77% in placebo.
3.2 Testosterone Enhancement in Athletes
Henkel et al. (2014) investigated Tongkat Ali in male participants using 800 mg/day of a potent extract for five weeks. Results:
- Total testosterone increased by 15.1% (p = 0.0195)
- Free testosterone increased by 61.1% (p = 0.0001)
- Muscle force (handgrip strength) increased by 16.6%
- Hemoglobin concentration increased by 6.1% (p = 0.0188), enhancing oxygen delivery to muscle tissue
3.3 Long-Term Testosterone Support with Concurrent Training
Leitão et al. (2021) conducted a rigorous 6-month, double-blind, placebo-controlled, randomized trial specifically examining Tongkat Ali (800 mg/day) combined with concurrent training (aerobic + resistance exercise, 3×/week). The combination group showed significant improvements in erectile function, and testosterone levels increased in nearly 50% of participants, confirming the sustainability of hormonal benefits.
4. Safety Profile and Athletic Compliance
4.1 Absence of Adverse Effects
Across multiple clinical trials, Tongkat Ali has demonstrated excellent tolerability. Henkel et al. reported zero side effects in 25 participants over five weeks. The Leitão et al. 6-month trial similarly confirmed safety over extended use.
4.2 WADA Compliance
For competitive bodybuilders, the World Anti-Doping Agency (WADA) status is paramount. Tongkat Ali is not listed on the WADA Prohibited List and functions through natural endocrine modulation rather than exogenous hormone administration. Importantly, Tongkat Ali extracts do not alter the testosterone/epitestosterone ratio—a key biomarker used by WADA to detect testosterone doping.
✅ WADA compliant — No prohibited substances. Suitable for natural bodybuilding and tested athletes.
5. Synergistic Training Considerations
5.1 Optimal Dosage and Timing
- Extracts: 800–1200 mg daily of a high-quality extract standardized to eurycomanone content (leaf-derived preferred).
- Training integration: Best results occur when combined with progressive resistance training (60–80% 1RM) and adequate protein intake.
- Duration: Minimum 5 weeks for measurable hormonal changes; 6+ months for maximal body composition effects.
5.2 The Leaf Extract Advantage
Given the 17-fold higher eurycomanone concentration in leaves compared to roots, leaf extracts allow for effective dosing at higher bioactive compound levels and more consistent standardization due to increased marker compound concentrations.
6. Conclusion
The convergence of phytochemical and clinical evidence positions Tongkat Ali leaf extract as a superior natural intervention for bodybuilding enhancement. The Jusoh et al. (2015) phytochemical data overturns the traditional assumption that roots are the optimal plant part, revealing leaves as the richest source of eurycomanone—the primary anabolic quassinoid. When combined with established clinical benefits of increased lean mass, reduced adiposity, enhanced strength, and optimized free testosterone levels, Tongkat Ali leaf extract emerges as a scientifically validated, safe, and WADA-compliant ergogenic aid for natural bodybuilders seeking to maximize their genetic potential.
References
- Jusoh, S., Abd. Ghani, R., Wan Rasidah, W. A. K., & Ishak, M. F. (2015). Phytochemical assessment of multilocational tongkat ali (Eurycoma longifolia) in Peninsular Malaysia. Jurnal Teknologi, 77(3), 87–91.
- Hamzah, S., & Yusof, A. (2003). The ergogenic effects of Eurycoma longifolia Jack: A pilot study. British Journal of Sports Medicine, 37, 464–470.
- Henkel, R. R., Wang, R., Bassett, S. H., Chen, T., Liu, N., Zhu, Y., & Tambi, M. I. (2014). Tongkat Ali as a potential herbal supplement for physically active male and female seniors—A pilot study. Phytotherapy Research, 28, 544–550.
- Leitão, A. E., de Souza Vieira, M. C., Pelegrini, A., da Silva, E. L., & de Azevedo Guimarães, A. C. (2021). A 6-month, double-blind, placebo-controlled, randomized trial to evaluate the effect of Eurycoma longifolia (Tongkat Ali) and concurrent training. Maturitas, 145, 78–84.
- Lazarev, A., & Bezuglov, E. (2021). Testosterone boosters intake in athletes: Current evidence and further directions. Endocrines, 2(2), 109–120.