L-Tryptophan Vs L-Theanine: Which is Better for Sleep?
: L-Theanine and L-Tryptophan are two well-known amino acids used to support better sleep and relaxation, but they work in different ways. L-Theanine helps promote calmness by enhancing GABA activity, while L-Tryptophan supports the natural production of serotonin and melatonin—key hormones involved in mood and sleep regulation.
If you're deciding between the two, understanding their differences in mechanism, benefits, and ideal use cases can help you choose the one that best fits your needs.
Before exploring further, please read the disclaimer located at the end of this webpage.
Key Takeaways
- L-Theanine promotes relaxation and stress reduction by enhancing GABA and alpha brain waves, supporting better sleep.
- L-Tryptophan acts as a precursor to serotonin and melatonin, improving sleep quality and mood.
- No studies have combined L-Theanine and L-Tryptophan, but they may complement each other's effects.
- Recommended dosage: 250mg of L-Theanine and ≤220mg of L-Tryptophan per day.
- Consult your doctor before use to avoid potential drug interactions or side effects.
Comparison Table of L-Tryptophan and L-Theanine
| Feature | L-Theanine | L-Tryptophan |
| Type of Compound | Non-protein amino acid | Essential amino acid |
| Source | Green tea, rare mushrooms | Oats, bananas, milk, tuna, turkey, chocolate, etc. |
| Primary Mechanism | Enhances GABA activity | Precursor to serotonin and melatonin |
| Sleep Support | Promotes relaxation without causing drowsiness | Supports deep, restorative sleep |
| Mental Health Benefits | Reduces stress and anxiety, improves cognitive function |
Mood stabilization, stress reduction, support for depression and bipolar disorder
|
| Additional Benefits | Supports immunity, heart health, weight management, potential anti-cancer effects |
Cognitive function, PMS relief, pain modulation, liver support, smoking cessation
|
| Typical Dosage Range | 100–400 mg/day | 250–500 mg/day |
| Common Side Effects | Mild digestive discomfort, rare liver issues (when from green tea extract) |
Drowsiness, dizziness, nausea, GI issues, potential serotonin syndrome (if combined with SSRIs)
|
| Cautions | Caution with high caffeine intake, consult physician if on medications |
Avoid combining with antidepressants without medical supervision
|
| Ideal For | Stress-related sleep issues, anxiety, mental focus | Insomnia, disrupted sleep cycles, mood imbalances |
| Combination Use | Safe to combine with L-Tryptophan for synergistic sleep and mood support |
Complements L-Theanine well; combination may improve outcomes in stress-related or chronic sleep issues
|
L-Theanine Overview
What is L-Theanine?
L-Theanine is a naturally occurring amino acid, known for its role in promoting relaxation and improving sleep. Unlike common amino acids involved in protein synthesis, L-Theanine belongs to the group of non-proteinogenic amino acids and is primarily found in green tea and certain rare mushrooms (Baba et al., 2021).
In green tea leaves, L-Theanine is the predominant free amino acid, accounting for 40% to 70% of the total amino acid content, which is approximately 1% to 2% of the dry leaf weight (Chatterjee et al., 2016). This compound contributes to the tea’s mild umami flavor and natural sweetness, balancing the bitterness of caffeine.
L-Theanine Health Benefits
L-Theanine is not only known for its relaxing effect when enjoying green tea but also offers several potential physical and mental health benefits. Below are the standout benefits of L-Theanine based on scientific evidence:
Improves Sleep and Relaxation
L-Theanine is widely recognized for its ability to naturally support sleep by calming the central nervous system.
According to a study published in Frontiers in Nutrition, L-Theanine combined with GABA—an inhibitory neurotransmitter—improved sleep quality and duration in mice experiencing insomnia caused by caffeine intake. This combination may promote GABA receptor expression, making it easier to fall asleep and achieve deeper sleep (Chatterjee et al., 2016).
Ph.D. in Molecular Medicine (Cell Physiology) also noted:
"The effect of a particular sleep aid had on our ability to sleep — that sleep aid is L-theanine — and there was some nuance to how it affects our sleep, so I'd encourage that."
Reduces Stress and Anxiety
L-Theanine helps alleviate stress and anxiety by balancing serotonin and dopamine—two key neurotransmitters involved in mood regulation.
One study showed that L-Theanine may improve hippocampal activity—an area of the brain related to memory and emotions—by altering glutamate and methionine levels, resulting in reduced anxiety [3].
Enhances Learning and Cognition
L-Theanine regulates neurotransmitters such as serotonin, dopamine, and GABA, which can improve cognitive function and focus. A Japanese study found that taking L-Theanine for 12 weeks enhanced working memory and attention-shifting ability in participants [1].
Boosts Immune System
This compound has also been shown to strengthen the immune system, helping prevent colds and flu. L-Theanine may counteract immune suppression caused by stress or intense physical activity by regulating the P38 and PPAR-γ signaling pathways (Saha et al., 2024).
Supports Heart Health
L-Theanine may protect heart health by inhibiting the JAK2, STAT3, and ERK1/2 signaling pathways—factors involved in endothelial cell formation—thereby reducing the risk of atherosclerosis and cardiovascular diseases (Chatterjee et al., 2016).
Weight Management
Animal studies suggest that L-Theanine can enhance the activity of brown and subcutaneous white fat metabolism while lowering blood cholesterol levels, aiding in weight control and obesity prevention [2, 3].
Anti-Tumor and Anti-Cancer Effects
In both in vitro and in vivo studies, L-Theanine and its derivatives have shown the potential to inhibit lung cancer cell growth by affecting EGFR/VEGFR-Akt/NF-kappa B signaling pathways, which play critical roles in cancer cell survival and proliferation [3, 11]. While these results are promising, more human clinical trials are necessary to validate these findings.
L-Theanine Side Effects
L-Theanine is generally considered safe when used at appropriate doses, with few serious side effects reported. In some cases, mild reactions may occur, such as:
- Digestive discomfort: Nausea or stomach upset, especially at high doses or when derived from green tea extract.
- Caffeine-related effects: When consumed through green tea, accompanying caffeine may cause restlessness, insomnia, or irritability (Saha et al., 2024).
- Rare liver concerns: Isolated reports have linked green tea extract to liver injury, though a direct connection to L-Theanine remains unclear [11].
The U.S. Food and Drug Administration (FDA) has granted L-Theanine GRAS (Generally Recognized As Safe) status for doses up to 250 mg per serving [11]. In Japan, it has been approved as a safe food additive since 1964 [2].
While well-tolerated by most individuals, it’s advisable to consult a healthcare professional before use—particularly if taking medications or managing underlying health conditions.
L-Tryptophan Overview
What is L-Tryptophan?
L-Tryptophan is an essential amino acid that plays a vital role in various biological functions in the body. Unlike some other amino acids, the human body cannot produce L-Tryptophan on its own and must obtain it through diet or supplements.
L-Tryptophan is found in various food sources, including oats, bananas, prunes, milk, tuna, cheese, bread, chicken, turkey, peanuts, and chocolate.
One of its most important functions is acting as a precursor for serotonin—a neurotransmitter that regulates mood, sleep, and appetite. Additionally, L-Tryptophan contributes to the production of melatonin—the hormone that controls the sleep-wake cycle—and niacin (Vitamin B3), which supports energy metabolism and nervous system health [6].
L-Tryptophan Health Benefits
Beyond its role in protein synthesis, L-Tryptophan has been associated with a variety of health benefits, particularly for sleep, mood, and nervous system function. Research highlights the following potential effects:
- Improved Sleep Quality: As a precursor to serotonin and melatonin, L-Tryptophan supports circadian rhythm regulation and promotes deep, restorative sleep [6, 7, 8, 9].
- Mood Support and Stress Reduction: It may help reduce cortisol—the primary stress hormone—and enhance serotonin production in the brain, leading to better emotional balance and reduced anxiety [5, 6, 7, 8].
- Support for Depression and Bipolar Disorder: When used alone or in combination with treatments like lithium, L-Tryptophan has shown potential in managing depression and bipolar symptoms.
- Enhanced Cognitive Function: By increasing its ratio to other large neutral amino acids in the bloodstream, L-Tryptophan improves brain uptake and boosts serotonin synthesis—supporting focus, mood stability, and cognitive performance during stress [8].
- Pain Modulation and Mechanical Sensitivity: L-Tryptophan may influence serotonin-mediated pain pathways and suppress pain-related neurotransmitters like substance P. It also activates the kynurenine (KYN) pathway via indoleamine 2,3-dioxygenase (IDO), aiding in pain perception regulation [8].
- Relief from Premenstrual Symptoms (PMS): Evidence suggests L-Tryptophan may ease mood swings, irritability, and emotional stress prior to menstruation.
- Smoking Cessation Support: Its calming effects may help manage nicotine withdrawal symptoms by reducing anxiety and irritability.
- Reduction in Bruxism and Facial Muscle Pain: Preliminary findings indicate it may alleviate stress-related behaviors such as teeth grinding and associated jaw discomfort.
- Exercise Performance Enhancement: L-Tryptophan may delay central fatigue during physical exertion, helping improve endurance in certain individuals.
- Liver Health Support: Animal studies show that L-Tryptophan supplementation may reduce liver fat accumulation and restore key enzyme functions, potentially offering protection against non-alcoholic fatty liver disease (NAFLD) [13].
L-Tryptophan Side Effects
L-Tryptophan may cause side effects when taken at high doses or over extended periods. Common side effects include drowsiness, dizziness, dry mouth, heartburn, nausea, diarrhea, headache, blurred vision, muscle weakness, loss of coordination, and sexual dysfunction.
In rare cases, more serious reactions may occur, such as extreme fatigue, tremors, skin changes, swelling, numbness, or irregular heartbeat. These may be linked to eosinophilia–myalgia syndrome (EMS), a rare but potentially life-threatening condition requiring immediate medical attention.
L-Tryptophan may also interact with selective serotonin reuptake inhibitors (SSRIs), increasing the risk of serotonin syndrome, which may present as agitation, rapid heartbeat, or elevated blood pressure. Caution is advised when combining it with medications that affect serotonin levels.
Although short-term animal studies suggest L-Tryptophan is relatively safe, these findings do not fully translate to humans. Prolonged or high-dose use may disrupt brain chemistry and increase the risk of adverse effects.
L-Tryptophan vs L-Theanine: Which is Better for Mental Health & Sleep Quality
L-Theanine promotes relaxation without causing drowsiness by enhancing GABA activity, making it ideal for stress-induced sleep issues. In contrast, L-Tryptophan supports deeper, more restorative sleep by serving as a precursor to serotonin and melatonin—key neurotransmitters for mood regulation and circadian rhythm [4,7,12}.
If your primary concern is anxiety or pre-sleep restlessness, L-Theanine may be the better choice. For those with insomnia or disrupted sleep cycles, L-Tryptophan could offer more direct benefits. Depending on individual needs, either compound—or a combination—can support mental well-being and sleep quality effectively.
Can You Combine L-Tryptophan and L-Theanine Together?
Combining L-Tryptophan and L-Theanine is entirely feasible and may enhance sleep quality through complementary mechanisms. L-Theanine promotes relaxation by activating GABA pathways, while L-Tryptophan supports the production of serotonin and melatonin—key neurotransmitters involved in mood regulation and sleep-wake cycles [6,7].
Although no studies have specifically examined the combined effects of these compounds, individual research suggests they may produce synergistic benefits, especially for individuals experiencing stress-related sleep disturbances.
Suggested Dosages:
- L-Theanine: 100–400 mg/day [14]
- L-Tryptophan: 250–500 mg/day [12]
Possible side effects include excessive drowsiness or mild digestive discomfort. To ensure safety, start with the lowest effective dose and monitor your body’s response. Individuals taking antidepressants, sedatives, or undergoing psychiatric treatment should consult a healthcare professional before combining these supplements.
How to Take L-Tryptophan and L-Theanine Together
If you struggle with insomnia or restless sleep, it can significantly impact your quality of life, leaving you feeling tired and unfocused the next day. If you're looking for a natural solution to improve your sleep, combining L-Tryptophan and L-Theanine could be a worthwhile option.
Adding these two amino acids to your diet through foods like bananas, milk, or green tea is a natural way to support sleep.
However, this method may not be the most effective since the amounts in food are relatively low and difficult to measure. For example, one cup of green tea contains only about 25 mg of L-Theanine, while the beneficial dose for sleep is around 250 mg – which would require drinking up to 10 cups of tea [11].
Instead, dietary supplements may offer a more efficient solution. Well-researched supplements help ensure precise dosages while minimizing the risk of combining conflicting compounds that may naturally occur in food. When using supplements, the commonly recommended dose is 250 mg of L-Theanine and no more than 220 mg of L-Tryptophan per day [6].
Although both substances are generally considered safe, individual responses can vary. To avoid unwanted side effects, it's best to start with a low dose and observe how your body reacts. Those with underlying health conditions, pregnant women, or breastfeeding mothers should consult a healthcare professional before taking any supplements.
Better sleep not only helps you feel more alert but also enhances your overall quality of life. Be patient, listen to your body, and find the solution that works best for you.
Conclusion
L-Theanine and L-Tryptophan are both promising nutrients for improving sleep and mental health, but they work through distinct mechanisms. Choosing the right option depends on your specific needs. However, there is no one-size-fits-all solution. Combining both nutrients in supplements could offer comprehensive support, but it's essential to consult with a healthcare professional.
References
- [1] Baba, Y., Inagaki, S., Nakagawa, S., Kaneko, T., Kobayashi, M., & Takihara, T. (2021). Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study. Journal of Medicinal Food, 24(4), 333–341. https://doi.org/10.1089/jmf.2020.4803
- [2] Chatterjee, S., Chatterjee, A., & Bandyopadhyay, S. K. (2016). L-Theanine: A Prospective Natural Medicine. International Journal of Pharmaceutical Sciences Review and Research, 41(2 21), 95–103. https://www.researchgate.net/publication/312021357_L-Theanine_A_Prospective_Natural_Medicine/
- [3] Li, M.-Y., Liu, H.-Y., Wu, D.-T., Kenaan, A., Geng, F., Li, H.-B., Gunaratne, A., Li, H., & Gan, R.-Y. (2022). L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications. Frontiers in Nutrition, 9. https://doi.org/10.3389/fnut.2022.853846
- [4] Lim, S. E., Kim, H. S., Lee, S., Kang, E. Y., Lim, J.-H., Kim, B.-Y., Shin, S.-M., & Baek, Y. (2024). Dietary supplementation with Lactium and L-theanine alleviates sleep disturbance in adults: a double-blind, randomized, placebo-controlled clinical study. Frontiers in Nutrition, 11. https://doi.org/10.3389/fnut.2024.1419978
- [5] Murphy, F., Smith, K., Cowen, P., Robbins, T., & Sahakian, B. (2002). The effects of tryptophan depletion on cognitive and affective processing in healthy volunteers. Psychopharmacology, 163(1), 42–53. https://doi.org/10.1007/s00213-002-1128-9
- [6] Nayak, B., Singh Buttar, H., & Buttar, H. (2015). Health Benefits of Tryptophan in Children and Adults. J.PHARM.SCI.TECH.MGMT, 1, 2015. https://pharmacy.nmims.edu/docs/dr-nayak-and-buttar-02.pdf
- [7] Prescott, S., Billeci, N., Gotcher, M., Patel, S., Almon, A., Morgan, H., Abukhalaf, D., & Groer, M. (2025). Tryptophan as a biomarker of pregnancy-related immune expression and modulation: an integrative review. Frontiers in Reproductive Health, 6. https://doi.org/10.3389/frph.2024.1453714
- [8] Rezende, R. M., Coimbra, R. S., Kohlhoff, M., Favarato, L. S. C., Martino, H. S. D., Leite, L. B., Soares, L. L., Encarnação, S., Forte, P., de Barros Monteiro, A. M., Peluzio, M. do C. G., & José Natali, A. (2024). Effects of Tryptophan and Physical Exercise on the Modulation of Mechanical Hypersensitivity in a Fibromyalgia-like Model in Female Rats. Cells, 13(19), 1647. https://doi.org/10.3390/cells13191647
- [9] Richard, D. M., Dawes, M. A., Mathias, C. W., Acheson, A., Hill-Kapturczak, N., & Dougherty, D. M. (2009). L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications. International Journal of Tryptophan Research, 2(2), IJTR.S2129. https://doi.org/10.4137/ijtr.s2129
- [10] Ritsner, M. S., Miodownik, C., Ratner, Y., Shleifer, T., Mar, M., Pintov, L., & Lerner, V. (2011). L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study. The Journal of Clinical Psychiatry, 72(1), 34–42. https://doi.org/10.4088/JCP.09m05324gre
- [11] Saha, U., Gupta, P., & Singh, M. (2024). L-Theanine an Astounding Amino Acid in Tea, Its Synthesis and Health Benefits: A Review. International Journal of Biochemistry Research & Review, 33(2), 21–32. https://doi.org/10.9734/ijbcrr/2024/v33i2855
- [12] Sutanto, C. N., Loh, W. W., & Kim, J. E. (2021). The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Nutrition Reviews, 80(2). https://doi.org/10.1093/nutrit/nuab027
- [13] Yanko, R., Mikhail Levashov, Chaka, O. G., Nosar, V., Sergey Khasabov, & Iryna Khasabova. (2023). Tryptophan Prevents the Development of Non-Alcoholic Fatty Liver Disease. Diabetes Metabolic Syndrome and Obesity, Volume 16, 4195–4204. https://doi.org/10.2147/dmso.s444278
- [14] Zhang, Y., Jia, X., Chen, X., Liu, Y., Zhao, Z., Hao, J., Wu, R., Feng, H., & Ren, X. (2021). L-theanine and Neumentix mixture improves sleep quality and modulates brain neurotransmitter levels in mice. Annals of Palliative Medicine, 10(4), 4572–4581. https://doi.org/10.21037/apm-21-663
- [15] Reddit - Dive into anything. (2024). Reddit.com. https://www.reddit.com/r/HubermanLab/comments/1bmfkbd/side_effects_of_theanine_anyone_else/?rdt=35466
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