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7 Scientifically Verified Benefits of L-Tryptophan – Better Cognition, Mood, and Sleep

L-Tryptophan is a dietary supplement for improving mood. However, many people don’t understand the full L-Tryptophan benefits. In this article, we explore the top 7 scientifically verified benefits of L-Tryptophan.

Many foods with L-Tryptophan are useful for getting a good dose of this powerful amino acid. However, the best way to experience the top L-Tryptophan benefits is by taking a high-quality dietary supplement.

If you want to learn more about the L-Tryptophan structure, or if you’re still wondering “what is L-Tryptophan?” then read through our informative L-Tryptophan product description. Or, read on to learn about the top L-Tryptophan benefits.

L-tryptophan benefits for memory Evidence suggests that L-Tryptophan is able to boost mental focus and memory

Top L-Tryptophan Sources

Nutrition Data, an offshoot of Self Magazine, has become one of the most authoritative nutrition facts websites since its launch in 2003. Its goal is to provide unbiased, comprehensive nutritional information for the general public. The website lists information that has been sourced from both the USDA's National Nutrient Database for Standard Reference and the manufacture’s information sheets for the products reviewed.[1]

Nutrition Data listed the top dietary sources of L-Tryptophan. Their nutrition experts stated that the top sources of L-Tryptophan are: first, sea lion kidney and second, sea lion meat. Since these are not common foods for most people, we’ll omit them from the following list:

(Ranked in milligrams of L-Tryptophan per 200 calorie serving):

  1. Game meat  (746 mg)
  2. Raw spirulina seaweed   (739 mg)
  3. Soy protein isolate   (695 mg)
  4. Dried, powdered egg white   (673 mg)
  5. Low-fat sesame seed flour   (659 mg)
  6. Dried spirulina seaweed   (641 mg)
  7. Raw crab meat   (607 mg)
  8. Soy sauce    (603 mg)
  9. Chopped spinach   (594 mg)
  10. Cooked Halibut fish with skin   (593 mg) [2]


While these food sources are all very high in L-Tryptophan, many of them are also high in other amino acids, which may compete with L-Tryptophan for absorption. As we explore later, studies have shown that carbohydrate-rich, protein-poor meals are best for improving L-Tryptophan absorption.

L-Tryptophan benefits for health Spirulina is a great natural source of L-Tryptophan

The best way to improve your L-Tryptophan levels is to use a high-quality L-Tryptophan dietary supplement. Scientists have verified the following seven benefits of using L-Tryptophan supplements:


1.    L-Tryptophan and Cognition

L-Tryptophan has a complex role in cognition. First and foremost, L-Tryptophan is the chemical precursor to serotonin (5-HT). Your body converts L-Tryptophan into serotonin through a multi-step process using enzymes called tryptophan hydroxylase and aromatic L-amino acid decarboxylase. [3]

Serotonin’s role in cognitive performance is well studied and is in the processes of being fully elucidated through ongoing research. Low serotonin levels are strongly correlated to impaired cognitive performance – especially memory formation. Furthermore, researchers have suggested using serotonin receptors as targets for improving cognition in depression and Alzheimer’s disease. [4]

However, the relationship between serotonin, L-Tryptophan, and cognition is not completely understood. Studies have indicated that L-Tryptophan may affect cognition differently in different individuals.


Specifically, a 2003 review found that L-Tryptophan depletion impaired memory but slightly improved attention. Furthermore, the authors of the review found that L-Tryptophan depletion impaired problem-solving abilities in people with a family history of bipolar and depression, but improved problem-solving in people with an otherwise healthy family history. [5]

In a 2006 clinical study, researchers found that L-Tryptophan supplements induced a positive bias in processing emotional material. In other words, L-Tryptophan improved mood and generated a positive outlook. However, these results were only relevant to the female volunteers who participated in the study – not the men. [6]

What we definitely know is that the role of L-Tryptophan in human cognition is complex and requires further research to fully understand its effects. It is, however, understood that L-Tryptophan supplements positively affect memory in humans. [7]

intelligence brain function with gears and cogs in the mind as an ancient grunge old medical parchment Studies have shown that L-Tryptophan helps to improve memory and cognition

2.    L-Tryptophan and Mood

In 2016, scientists published an in-depth review about how L-Tryptophan and serotonin affect mood and cognition. The review was published in Nutrients, a distinguished academic journal for nutrition research.

According to studies cited by the researchers, L-Tryptophan depletion has a varied effect on mood. In a similar way to how it affects cognition, L-Tryptophan appears to affect people’s moods based on whether or not they have a personal or family history of depression or anxiety. It is clear that improved L-Tryptophan levels are consistently associated with a better mood. Also, people with a history of depression are more susceptible to mood changes based on L-Tryptophan levels. [8]


Another study, published in 2015, on 59 healthy middle-aged women found that daily L-Tryptophan supplements (0.5grams twice daily) ‘improved emotional processing’ and boosted overall mood. The experiment was conducted over 19 days and the results showed improved mental alertness, mood boost, and a feeling of happiness when taken before bed. [9]

L-Tryptophan supplements improve sleep patterns. Researchers now believe that this is another reason to support using L-Tryptophan for mood improvements. The effects of sleep on mood are well understood - both the length and quality of sleep are important in maintaining a good mood. [10]

3.    L-Tryptophan for Stress-Relief

In addition to improving mood, many people use L-Tryptophan to reduce feelings of stress. This is often a byproduct of the improved mood and better sleep that result from using L-Tryptophan supplements.

Liftmode l-tryptophan Liftmode's L-tryptophan, 98+% purity

Studies have looked into L-Tryptophan’s effects on stress in both humans and animals. The results are encouraging. For example, the first human study available was published in 1985. Researchers looked at the effects of L-Tryptophan supplements on ten outpatients suffering from various states of anxiety. The supplements resulted in a significant reduction in anxiety scores for all patients. [11]

However, the 1985 study used L-Tryptophan in conjunction with a chemical agent used to reduce the activity of dopamine decarboxylase (theoretically strengthening L-Tryptophan’s effects).


Another study, published in 1986, looked into the effects of childbirth on natural L-Tryptophan levels. Women who suffered from post-childbirth ‘blues’ tended to have lower L-Tryptophan levels and higher cortisol levels compared to those who didn’t. [12]

More recently, a study published in 2014 looked into the effects of an L-Tryptophan-rich diet on stress-induced alcohol desire in chronic binge drinkers. The binge drinkers who were given a diet rich in L-Tryptophan had a reduced craving for alcohol compared to those receiving the control diet. The scientists concluded that this was an indication that L-Tryptophan could moderate stress response. [13] Interestingly, the desire for a drink in non-binge drinkers actually increased with the L-Tryptophan-rich diet. Although this did not indicate an increase in stress, it showed that L-Tryptophan may work differently in people with different behavior types.


Finally, scientists now believe that people’s individual responses to L-Tryptophan may be genetically predetermined. For example, a 2015 study found that variations on the 5-HTTLPR genotype resulted in different stress responses to L-Tryptophan supplements. [14]

girl with sunflower, happy Studies have found that L-Tryptophan supplements help to improve mood and reduce stress

4.    L-Tryptophan for Sleep

This is one of the key benefits of L-Tryptophan and has been very well studied in the past. Scientists have verified that L-Tryptophan improves both the time to fall asleep as well as the quality of sleep.

In fact, in 1986, a review of the literature was published on using L-Tryptophan as a therapeutic supplement for insomnia. The authors concluded that L-Tryptophan could be used effectively to induce sleep at a dose of between 1 – 15 grams on the first night. For chronic sleep impairment, a low dose could be used repeatedly to improve sleep quality. Extra benefits include the lack of side-effects and the absence of developing tolerance, even when using L-Tryptophan for longer periods of time. [15]


One of the most important aspects of using L-Tryptophan for sleep is that it is effective at improving melatonin levels. Melatonin is known as the ‘sleep hormone’ and helps to promote sleep. L-Tryptophan is converted into serotonin in your body. Excess serotonin is then converted into melatonin in the pineal gland, in response to dark-light cycles and other factors. [16]

Even low doses of L-Tryptophan, such as what we would normally consume in our daily diets, have been reported to improve sleep quality. In a 1979 study, the time to fall asleep was significantly improved with just 1 gram of L-Tryptophan. A dose as low as 250 mg was effective at improving stage IV sleep. [17]


Scientists have even suggested using L-Tryptophan to aid in improving the symptoms of sleep apnea. Just 2.5 grams of L-Tryptophan taken before bed significantly improved sleep respiration in volunteers with obstructive sleep apnea (but not central sleep apnea). The L-Tryptophan supplement also lengthened the REM sleep and reduced REM latency in all volunteers. [18]


5.    L-Tryptophan and Exercise Performance

A lesser-known benefit of L-Tryptophan is that it has the ability to improve exercise performance. Again, although this has been studied in-depth by scientists over the past few decades, the knowledge of these benefits seem to have missed most people.

In 1988, scientists published a study on the effects of L-Tryptophan on exercise in the International Journal of Sports Medicine. Twelve healthy volunteers participated in the study, in which they were required to run on a treadmill until exhaustion. A number of factors were measured.

Remarkably, the group receiving L-Tryptophan had a 49.4% longer time to exhaustion than the placebo group. Not only this, but those taking L-Tryptophan had a lower perception of exertion. No physiological measures like maximum heart rate, peak oxygen consumption, or pulse recovery rate were affected by the L-Tryptophan supplement. [19]


100grams L-Tryptophan from Liftmode,99+% purity 100grams L-Tryptophan from Liftmode,99+% purity

A second study, published in 2015 in the International Journal of Neuroscience, found similar results. Twelve healthy athletes performed a 20-minute cycle on a cycle ergometer at 50% of their exercise capacity. Each volunteer did one round with L-Tryptophan and another without, in a double-blind, randomized manner. The results showed that with placebo, the average distance covered in the last 20 minutes was 12’000m, while the average distance with L-Tryptophan was closer to 12’600m – a statistically significant improvement. [20]


The theory underlying L-Tryptophan’s ability to improve exercise performance is that, more often than not, people stop their physical exercise not because of muscle fatigue but because of perceived exertion and a lack of neural drive. It seems that altering the serotonin system with L-Tryptophan positively enhances the neural drive and boosts exercise performance. [21]


6.    L-Tryptophan and Psychiatric Disorders

A vast amount of research has gone into the use of L-Tryptophan in people suffering from various neurological disorders including anxiety, depression, or panic disorder. This is due to the important role of the serotonin system in human psychology and brain function.

A 2008 review published in the International Journal of Tryptophan Research looked into all the published data to date on the use of L-Tryptophan for panic disorders. The authors concluded that a large amount of research had considerably improved knowledge of the role of the serotonin system. However, the way that L-Tryptophan works is complex.

It seems that L-Tryptophan affects different people in different ways, depending on the expression of various genes. There is also a difference between how L-Tryptophan affects men and women. Interestingly, this difference is mirrored in the likelihood of developing panic disorder – women are twice as likely as men to suffer from the disorder. [22]

A 2002 review of the published studies on L-Tryptophan and depression examined over 108 separate trials. However, of these, only 2 trials were of sufficient quality to meet the inclusion criteria! Both the trials showed that L-Tryptophan or 5-HTP were significantly better than placebo at alleviating symptoms. However, more quality research is required to better understand the role of L-Tryptophan in depression. [23]


Most recently, a study published in 2016 examined a new line of research about L-Tryptophan and depression. The authors found evidence that depression may be linked to a biochemical change in the metabolism of L-Tryptophan. So, instead of being converted to serotonin, it is converted into neurotoxins like quinolinic acid, for example. The reasons for this are proposed to be due to increased stress hormones and inflammation. So, it may actually be a bad idea to take L-Tryptophan if you have depression. [24]


happy couple sleeping in a comfortable bed at home L-Tryptophan has benefits in helping to promote healthy sleep

7.    L-Tryptophan for Weight

The role of L-Tryptophan in managing weight is not well understood, and there are a number of studies with conflicting results. However, it does not seem that L-Tryptophan can reduce weight directly. A 1985 study published in the Journal of Obesity Studies was entitled: “L-Tryptophan does not increase weight loss for carbohydrate-craving obese subjects”.

The study found that supplementing with L-Tryptophan did not significantly increase weight loss in obese volunteers. However, although the results weren’t statistically significant, there was a slight decrease in total body weight for the eight subjects who complete the study with L-Tryptophan – compared to those who took a placebo. The mean weight loss for those on placebo was 1.1kg over 6 weeks, while those taking an L-Tryptophan supplement lost an average of 2.3kg. [25]


One of the key ways that researchers think that chemicals which target serotonin receptors may lead to weight loss is through blocking the cravings for carbohydrates. Serotonin has a complex role in mediating your appetite, this much is known for sure.

For example, eating a meal that is rich in carbohydrates and with relatively low protein levels – a meal that is high in vegetables, starch, and fruit, for example – allows your body to produce the proteins required to transport L-Tryptophan into your brain. This can then be converted into serotonin, which mediates appetite.

However, a meal that is high in protein and low in carbohydrates supplies your body with a large number of amino acids which compete with L-Tryptophan. As a result, less L-Tryptophan can be transported into your brain, which then produces less serotonin. [26] Quite clearly, this indicates the important role of L-Tryptophan in mediating appetite through its effects on serotonin.


In conclusion, L-Tryptophan is a great supplement with a number of scientifically-verified health benefits. Most importantly, L-Tryptophan positively affects mood and cognition. These effects are best seen in women and in people with a family history of mood disorders.

Research has also indicated that L-Tryptophan positively affects your stress levels and helps to improve sleep quality. L-Tryptophan’s influence on sleep is highly underrated considering the vast amount of research showing its positive sleep-enhancing benefits.

Even less well-known is L-Tryptophan’s ability to improve exercise performance through the serotonin system. It enhances neural drive and helps to lengthen exercise stamina. Although L-Tryptophan supplements have not yet been established to have a directly positive effect on weight, their influence on stress, mood, cognition, sleep, and exercise, may indicate the potential for an indirect positive effect on your weight.

couple man and woman travelers backpackers L-Tryptophan supplements are a great way to boost your mood and add to a healthy lifestyle


[1]About NutritionData.com”, Self Nutrition Data: Know What you Eat, available online, accessed April 18, 2017

ferent ways, depending on theirusing L-Tryptophan supplements: gh-qaulity dietary supplement.  amino acids, which may compete w

[2]Foods highest in Tryptophan”, Self Nutrition Data: Know What you Eat, available online, accessed April 18, 2017

[3] A Slominski et al., “Conversion of L-tryptophan to serotonin and melatonin in human melanoma cells”, FEBS Letters, Volume 511, Issues 1–3, 30 January 2002, Pages 102–106

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[5] WJ. Riedel et al., “Tryptophan Modulation and Cognition”,Developments in Tryptophan and Serotonin Metabolism, Volume 527 of the series Advances in Experimental Medicine and Biology pp 207-213

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[7] D Mendelsohn et al., “Effects of acute tryptophan depletion on memory, attention and executive functions: a systematic review”, Neurosci Biobehav Rev. 2009 Jun;33(6):926-52. doi: 10.1016/j.neubiorev.2009.03.006.

[8] FM van der Veen et al., “Effects of acute tryptophan depletion on mood and facial emotion perception related brain activation and performance in healthy women with and without a family history of depression”, Neuropsychopharmacology. 2007 Jan;32(1):216-24. Epub 2006 Oct 4.

[9] MH Mohajeri et al., “Chronic treatment with a tryptophan-rich protein hydrolysate improves emotional processing, mental energy levels and reaction time in middle-aged women”, Br J Nutr. 2015 Jan 28;113(2):350-65. doi: 10.1017/S0007114514003754. Epub 2015 Jan 9.

[10] Silber BY, Schmitt JA, “Effects of tryptophan loading on human cognition, mood, and sleep”, Neurosci Biobehav Rev. 2010 Mar;34(3):387-407. doi: 10.1016/j.neubiorev.2009.08.005. Epub 2009 Aug 26.

[11] Kahn RS, Westenberg HG, “L-5-hydroxytryptophan in the treatment of anxiety disorders”, J Affect Disord. 1985 Mar-Apr;8(2):197-200.

[12] SL Handley et al., “Tryptophan, cortisol and puerperal mood”, Br J Psychiatry. 1980 May;136:498-508.

[13] J Nesic, T Duka, “Effects of stress and dietary tryptophan enhancement on craving for alcohol in binge and non-binge heavy drinkers”, Behav Pharmacol. 2014 Sep;25(5-6):503-17. doi: 10.1097/FBP.0000000000000067.

[14] H Cerit et al., “The effect of tryptophan on the cortisol response to social stress is modulated by the 5-HTTLPR genotype”, Int J Psychoneuroendocrinology, February 2013, Volume 38, Issue 2, Pages 201–208

[15] TA Jenkins et al., “Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis”, Nutrients. 2016 Jan; 8(1): 56, doi:  10.3390/nu8010056

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[19] Segura R, Ventura JL, “Effect of L-tryptophan supplementation on exercise performance”, Int J Sports Med. 1988 Oct;9(5):301-5

[20] C Javierre et al., “L-tryptophan supplementation can decrease fatigue perception during an aerobic exercise with supramaximal intercalated anaerobic bouts in young healthy men”, Int J Neurosci. 2010 May;120(5):319-27. doi: 10.3109/00207450903389404.

[21] MO Melancon et al., “Exercise increases tryptophan availability to the brain in older men age 57-70 years”, Med Sci Sports Exerc. 2012 May;44(5):881-7. doi: 10.1249/MSS.0b013e31823ede8e.

[22] E Maron et al., “Tryptophan Research in Panic Disorder”, Int J Tryptophan Res. 2008; 1: 3–12

[23] R Sandyk, “L-tryptophan in neuropsychiatric disorders: a review”, Int J Neurosci. 1992 Nov-Dec;67(1-4):127-44.

[24] L Dell'Osso et al., “Depression, Serotonin and Tryptophan”, Curr Pharm Des. 2016;22(8):949-54

[25] GW Strain et al., “L-tryptophan does not increase weight loss in carbohydrate-craving obese subjects”, Int J Obes. 1985;9(6):375-80.

[26] RJ Wurtman, JJ Wurtman, “Carbohydrate craving, obesity and brain serotonin”, Appetite. 1986;7 Suppl:99-103.