L-Tryptophan Vs L-Theanine: Which is Better for Sleep?
If you've ever tossed and turned at night, counting hundreds of sheep with your eyes still wide open — you're not alone. Statistics show that 35% of the global population struggles with poor sleep quality. In today's fast-paced world, a good night's sleep feels more like a luxury than a basic need.
In the quest for restful sleep, L-Tryptophan and L-Theanine have emerged as two promising contenders. But choosing between them is like standing at a fast-food counter, torn between fries and onion rings — both are tempting, but you'll always wonder if you're missing out on something better.
Let’s dive into this article to discover which one is the best fit for your sleep needs and mental well-being.
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 |
|
Source |
Mainly found in green tea |
Found in oats, bananas, milk, tuna, turkey, chocolate |
|
Mechanism of Action |
Enhances GABA activity, promoting relaxation and reducing anxiety |
Precursor to serotonin and melatonin, supporting sleep and mood regulation |
|
Primary Benefits |
Reduces stress, improves sleep quality, supports focus |
Promotes deep sleep, regulates mood, supports circadian rhythm |
|
Common Dosage |
250mg per day |
Should not exceed 220 mg per day |
|
Side Effects |
Mild, may cause headaches or drowsiness in some cases |
Relatively safe but may cause nausea, headaches, or drug interactions. |
|
Best Suited For |
People experiencing stress or nervousness affect sleep. |
People with sleep issues related to low serotonin or circadian rhythm disorders. |
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.
A unique characteristic of L-Theanine is its ability to separate easily from other tea components due to its insolubility in organic solvents like methanol and chloroform [11]. This property makes it easier for scientists to extract and use L-Theanine in dietary supplements and functional beverages.
With its pleasant taste and promising health benefits, L-Theanine is becoming an increasingly popular choice among those seeking natural ways to enhance relaxation and sleep quality.
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
Although L-Theanine is widely recognized for its benefits in supporting sleep and mental health, any supplement should be considered with potential side effects in mind.
Current scientific evidence suggests that L-Theanine is generally safe when taken in appropriate doses. However, there are a few precautions users should be aware of before incorporating this compound into their routine.
L-Theanine has been granted "Generally Recognized As Safe" (GRAS) status by the U.S. Food and Drug Administration (FDA), indicating that it is safe and non-toxic when consumed in doses of up to 250 mg per serving [11]. Since 1964, the Japanese Ministry of Health and Welfare has also approved L-Theanine as a safe food additive for consumers [2].
A clinical study by Ritsner et al. (2011) lasting 8 weeks found that taking 400 mg of L-Theanine daily did not cause any significant side effects in participants, further reinforcing its safety when used for extended periods at appropriate dosages [10].
However, some mild side effects may occur in certain cases, including:
-
Mild Digestive Issues: Taking L-Theanine from green tea extract or in high doses may cause stomach discomfort (Saha et al., 2024).
-
Liver Concerns: Rare reports of liver damage have been associated with green tea extract consumption, although a direct link to L-Theanine has not been clearly established [11].
In fact, according to comments on a Reddit topic about the side effects of L-Theanine [15], some users reported experiencing frequent urination at night, brain fog/forgetfulness, headaches, and short-term memory loss.*
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.
In nature, tryptophan exists in two isomeric forms: L-Tryptophan and D-Tryptophan, with L-Tryptophan being the predominant form found in higher organisms, including humans (Nayak et al., 2015). Once ingested, L-Tryptophan serves as “a building block” for essential proteins and enzymes.
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 is widely recognized for its potential health benefits for both physical and mental well-being.
By participating in the production of serotonin and melatonin—two crucial neurotransmitters—this amino acid can positively impact mood, sleep, and even pain perception. Scientific studies have shed light on several remarkable effects of L-Tryptophan on overall health.
Modulating Mechanical Sensitivity
L-Tryptophan may help reduce mechanical sensitivity in chronic pain conditions such as fibromyalgia. When metabolized into serotonin in the brain, this compound contributes to regulating the intensity of pain perception.
Animal studies indicate that L-Tryptophan can activate the enzyme indoleamine 2,3-dioxygenase (IDO), enhancing metabolism through the kynurenine (KYN) pathway, which is associated with pain management [8].
Enhancing Brain Function
L-Tryptophan plays a crucial role in boosting cognitive performance, particularly during stressful periods. When supplemented, this amino acid increases its ratio relative to other large neutral amino acids in the blood, improving its transport into the brain and promoting the production of serotonin—a neurotransmitter vital for stable mood and concentration [8].
Reducing Stress and Improving Mood
Several studies suggest that L-Tryptophan can lower cortisol—the stress hormone—in anxiety-inducing situations. This compound is considered a promising option for supporting the treatment of mental health disorders, especially when combined with other therapeutic interventions [5, 6, 7, 8].
Pain Relief
L-Tryptophan may alleviate pain by regulating serotonin's role in inhibiting pain-mediating substances such as substance P. This effect can be particularly beneficial for those suffering from chronic pain or neuropathic pain conditions [8].
Improving Sleep Quality
One of the most notable benefits of L-Tryptophan is its ability to promote better sleep quality. As a precursor to serotonin and melatonin—two key compounds involved in sleep regulation—L-Tryptophan can help those struggling with insomnia or difficulty falling asleep [6, 7, 8, 9].
Reducing Fat Accumulation and Supporting Liver Function
Beyond its neurological effects, L-Tryptophan may benefit liver health. Animal studies suggest that supplementation can reduce fat accumulation in the liver and restore the activity of key enzymes, offering protection against non-alcoholic fatty liver disease (NAFLD) [13].
L-Tryptophan Side Effects
While L-Tryptophan offers numerous health benefits, its supplementation can pose certain side effects, especially when taken in high doses or without proper guidance.
A study on mice showed that supplementing L-Tryptophan at doses up to 7.6 g/kg of food did not cause significant side effects, indicating the amino acid's short-term safety [8]. However, these results cannot fully confirm its safety at high doses for long-term use or in humans.
Animal studies provide preliminary safety insights, but differences in metabolism and physiological responses between animals and humans require caution when applying these findings to human health.
Most studies suggest that L-Tryptophan is safe when taken at appropriate doses. However, excessive intake can increase the risk of side effects or cause an imbalance in brain chemistry. One significant risk is its potential interaction with certain medications, especially antidepressants like selective serotonin reuptake inhibitors (SSRIs).
This combination can elevate serotonin levels in the body, potentially leading to serotonin syndrome — a condition that causes symptoms such as agitation, rapid heartbeat, or high blood pressure.
High doses of L-Tryptophan may also increase the likelihood of side effects like nausea, headaches, or insomnia. Therefore, individuals should consult a healthcare professional before using L-Tryptophan, particularly if they are taking other medications or have pre-existing medical conditions.
L-Tryptophan vs L-Theanine: Which is Better for Mental Health & Sleep Quality
L-Theanine and L-Tryptophan can be compared to two different paths leading to the same destination: quality sleep and a calm mind. The choice of which is better depends on each person's goals and health condition.
L-Theanine primarily works by promoting relaxation. Instead of knocking you out like a sedative, it gently pats you on the shoulder and says, "Relax, everything’s fine." It enhances the activity of GABA – a neurotransmitter that calms the nervous system [4].
One standout feature of L-Theanine is that it doesn’t cause drowsiness but simply helps the body relax, making it a suitable choice for those experiencing stress or restlessness that interferes with sleep.
On the other hand, L-Tryptophan plays a crucial role in sleep regulation by converting into serotonin and melatonin in the brain. Serotonin helps improve mood and supports sleep, while melatonin regulates the sleep-wake cycle, helping the body fall asleep faster and enjoy deeper sleep [7, 12].
In terms of application, L-Theanine may be ideal for people struggling with pre-sleep nervousness or tension. Meanwhile, L-Tryptophan may be more beneficial for individuals dealing with sleep disorders or needing support for deep sleep.
There is no definitive answer to which is better. L-Theanine helps with relaxation and anxiety relief, while L-Tryptophan directly regulates the sleep cycle. Depending on your personal needs, you can choose one or consider combining both to optimize sleep quality and mental well-being.
Can You Combine L-Tryptophan and L-Theanine Together?
Combining L-Tryptophan and L-Theanine may offer potential benefits for supporting sleep and mental health due to their complementary mechanisms of action.
Although no studies currently investigate the direct combination of these two amino acids, their distinct ways of working suggest that using them together could enhance sleep support.
L-Theanine primarily works by boosting the production of GABA, a neurotransmitter that calms the nervous system, helping to reduce stress and promote relaxation.
Meanwhile, L-Tryptophan serves as a precursor to serotonin and melatonin, which play essential roles in mood regulation and the body's sleep-wake cycle [6, 7]. This combination may provide both mental relaxation and improved sleep quality – making it an ideal option for those struggling with stress-related sleep disturbances.
While the potential benefits of this combination are promising, individual responses may vary. Possible side effects include excessive drowsiness, mild headaches, or digestive discomfort. To ensure safety, it's best to start with low doses and gradually increase them as the body adjusts.
Commonly recommended dosages based on individual studies are:
- L-Theanine: 100-400 mg/day [14].
- L-Tryptophan: 250-500 mg/day [12].
However, taking both supplements together should be done under medical supervision, especially for individuals taking antidepressants or sedative medications, to avoid possible drug interactions.
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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