L-Theanine Does Not Improve Testosterone Levels
There is no evidence that L-theanine supplementation improves testosterone levels in males with low testosterone. The provided clinical guidelines and research evidence do not mention L-theanine as a treatment option for hypogonadism, and it is not included in any evidence-based recommendations for testosterone management.
Evidence-Based Approaches for Low Testosterone
Lifestyle Modifications Should Be First-Line
- Weight loss through low-calorie diets can reverse obesity-associated secondary hypogonadism by improving testosterone levels and normalizing gonadotropins, though increases are modest (1-2 nmol/L) 1
- Physical activity shows similar benefits, with results correlating to exercise duration and weight loss 1
- Exercise training enhances lean body mass, aerobic fitness, and strength in aging men, and men who are physically able should be encouraged to exercise 2
- Adequate sleep, exercise, and weight loss in patients with obesity are imperative before implementing any nutraceutical agents 3
Limited Evidence for Nutraceutical Supplements
Among the supplements studied for testosterone enhancement, only a select few have shown any promise in well-controlled randomized trials 3:
- Zinc - May improve testosterone in deficient individuals 3
- Vitamin D - Only beneficial in cases of hypovitaminosis D 3
- L-arginine - Some evidence for testosterone improvement 3
- Mucuna and ashwagandha - Limited positive data 3
However, the effects of nonpharmacologic interventions on testosterone levels are modest and do not directly translate into clinical benefits 3.
Most Supplements Lack Evidence
- A systematic review of popular testosterone supplements found that only 24.8% had data showing an increase in testosterone, while 10.1% actually showed a decrease, and 61.5% had no data at all 4
- 90% of "testosterone booster" supplements claimed to boost testosterone, but these claims were not supported by the academic literature 4
- Many supplements contained supra-therapeutic doses of vitamins and minerals, occasionally exceeding the FDA upper tolerable intake level 4
- No whole supplement products have published randomized controlled trial evidence 5
When Testosterone Replacement Therapy Is Indicated
Diagnostic Criteria
- Two separate fasting morning testosterone measurements below 300 ng/dL are required for diagnosis, along with hypogonadal symptoms including decreased libido, erectile dysfunction, decreased physical stamina, depressed mood, and fatigue 6, 1
- Testosterone levels above 350 ng/dL typically do not require replacement therapy 6
- Testosterone levels below 230 ng/dL usually benefit from testosterone replacement therapy in symptomatic men 6
Treatment Options
If testosterone replacement is indicated, intramuscular or transdermal testosterone therapy results in small improvements in sexual functioning and quality of life 1:
- Moderate-certainty evidence shows small improvement in global sexual function 1
- Low-certainty evidence shows small improvement in quality of life 1
- Little to no effect on physical functioning, depressive symptoms, or cognition 1
Critical Pitfall to Avoid
Patients should be informed that over-the-counter "testosterone booster" supplements, including L-theanine, lack evidence to support their claims 5, 4. Instead of pursuing unproven supplements, focus on: