Effect of Eurycoma longifolia Extract on Anabolic
Balance During Endurance Exercise

Talbott S, Talbott J, Negrete J, Jones M, Nichols M, and Roza J.


Eurycoma longifolia, commonly known as “Tongkat Ali” or “Longjack,” is often touted as a testosterone “booster” and marketed to athletes as a training aid and performance enhancer. Rodent studies have shown oral delivery of Eurycoma extract to improve sexual performance and increase serum testosterone levels. Open-label human trials have suggested that Eurycoma extract may help prevent age-associated androgen deficiency, improve sexual function, and increase psychological parameters such as mood, energy, and sense of well-being.


The purpose of this study was to determine the effects of Eurycoma longifolia on testosterone and cortisol levels during intense endurance exercise.


We used a water-soluble extract of Eurycoma longifolia (E) standardized to 22% eurypeptides and 40% glycosaponins. Male subjects (N=30) were recruited from a 24- hour mountain biking event and asked to provide a saliva sample before and after each lap for measurement of cortisol and testosterone by enzyme immunoassay (Salimetrics, State College, PA). Subjects completed 4 laps (14.91 miles/lap) and provided 8 saliva samples over a 24h period. Subjects consumed 100mg of E (N = 15) or a look-alike placebo (P, N = 15) approximately 30 minutes prior to endurance exercise.


Cortisol levels were 32.3% lower in E compared to P (0.552+0.665 versus 0.816+0.775 ug/dL, P < 0.05). Testosterone levels were 16.4% higher in E compared to P (86.72+40.90 versus 72.47+33.77 pg/mL, P < 0.05).


These results suggest that Eurycoma longifolia extract may help to maintain normal levels of cortisol (low) and testosterone (high) and thus promote an overall “anabolic” hormonal state (versus a “catabolic” state characterized by elevated cortisol and suppressed testosterone) during intense endurance exercise.


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