What Is L-Tryptophan? A Comprehensive Overview

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This comprehensive overview will dive into what is L-tryptophan and how this amino acid functions in the human body. From its desirable attributes of promoting sleep and reducing anxious feelings, L-tryptophan plays an important role in quality of life.

Quick Look:

  • L-tryptophan is an essential amino acid that supports serotonin production and other biological functions. 
  • There are risks associated with misuse of L-tryptophan supplementation, including serotonin syndrome, and other interactions that should be avoided. Speak with a medical professional before beginning supplementation of L-tryptophan. 
  • The amino acid L-tryptophan can be used as a pet supplement to demote aggressive behavior and improve emotional well-being. 

An Overview of the Essential Amino Acid L-Tryptophan

An overview of l-tryptophan and its benefits.

How does tryptophan work to provide health benefits? As an amino acid, L-tryptophan promotes many advantages for sleep and mood and supports numerous bodily functions. Keep reading for more information on how L-tryptophan functions and how it can help you!


Tryptophan is an essential amino acid (EAA), meaning it must be consumed through dietary means as the human body does not naturally produce it. There are many tryptophan-rich foods that can produce the benefits from this amino acid, including spirulina, quinoa, and chicken. 

L-tryptophan and D-tryptophan are the two types of tryptophan that differ in molecular structure. D-tryptophan acts as a bacterial metabolite, while L-tryptophan is necessary for making proteins and other metabolic functions.  


What does L-tryptophan do?

Many benefits are associated with L-tryptophan, and supplements provide this valuable amino acid. One such example is L-tryptophan sleep supplements that promote improvements in sleep quality. 

L-tryptophan is linked to the synthesis of serotonin in the brain and can promote increases in the production of this neurotransmitter. Due to this important attribute of L-tryptophan, its benefits have been linked to treatments for various mood disorders. 

Benefits of L-Tryptophan:

  • Improves sleep
  • Reduces symptoms of anxiety
  • Decreases symptoms of depression
  • Enhances mood
  • Stimulates the production of serotonin 


So, what is L-tryptophan used for?

Though L-tryptophan for sleep is one of the most common uses of this essential amino acid, there are more ways this amino acid is useful. For example, L-tryptophan is productive in reducing mood symptoms in patients with premenstrual dysphoric disorder (PMDD) due to its functions in promoting serotonin synthesis. 

L-Tryptophan Uses:

  • Premenstrual dysphoric disorder
  • Attention deficit hyperactivity disorder (ADHD)
  • Depression
  • Anxiety
  • Sleep
  • Tourette’s syndrome 
  • Bruxism 

From our research, shown in the graph below, we asked surveyors what they used L-tryptophan for. 

Based on the results, we discovered that many individuals did not take L-tryptophan supplements. Those who did take L-tryptophan used the amino acid supplement mainly for anxiety relief and sleep improvements. 

A graph detailing the different uses of l-tryptophan.

Source: EverFlex Survey, 2024

Risks & Side Effects

Is L-tryptophan safe to take as a supplement? 

Like any supplement or medication out there, there are L-tryptophan side effects and risks associated with its use. Many side effects from L-tryptophan supplementation are minor, such as headaches or dry mouth.

L-Tryptophan Risks & Side Effects:

  • Diarrhea
  • Dizziness
  • Dry mouth
  • Eosinophilia myalgia syndrome (EMS)
  • Heartburn
  • Headache
  • Muscle weakness 

With tryptophan long-term use or high doses of tryptophan come potential risks such as serotonin syndrome, also called serotonin toxicity. This condition results from a surplus of serotonin in the brain. It can be caused by a range of things, including tryptophan supplementation, due to the amino acid’s ability to increase serotonin production. 


Can you take L-tyrosine and L-tryptophan together? 

Identifying possible life-threatening interactions is crucial when taking medications and supplements. For example, though no L-tyrosine and L-tryptophan interactions were found, that does not mean there are no potential interactions whatsoever. 

Consulting with your doctor before supplementation is vital for avoiding potential health risks. 

Avoid Interactions With:

  • Sedatives
  • Dextromethorphan 
  • Antidepressants
  • Pentazocine
  • Meperidine 
  • Phenothiazines 
  • Tramadol 

Dosing & Dietary Supplements 

How much tryptophan per day you should be taking depends on numerous factors, including age, weight, health conditions, and the reason for taking the supplement. It’s always safest to first speak with a medical professional to determine the best course of action on dosage and whether L-tryptophan supplements are best for you. 

Determining which form of purified tryptophan supplement, such as tryptophan liquid, is the next step.  

A graph detailing what forms of l-tryptophan supplements are the most popular.

Source: EverFlex Survey, 2024

Based on our research, a majority of people who take tryptophan supplements choose to take pills. These tend to be the easiest for people, as they lack flavor and are easy to take on-the-go versus a liquid supplement or meal planning to incorporate tryptophan-rich foods in their diet. 

The Importance of L-Tryptophan

L-tryptophan, one of the building blocks of protein, plays a vital role in everyday functions in the human body. It is necessary for the function and development of numerous organs.

After the EAA is converted to 5-HTP, or 5-hydroxytryptophan, it is converted into serotonin. The neurotransmitter serotonin is also a hormone connected to body temperature regulation, sleep, hunger, and mood. 

Studies on acute tryptophan depletion (ATD) have presented the risks of poor tryptophan intake. Some of these side effects of low tryptophan levels include aggression, poor mood, and clinical depression. The heavy correlation of tryptophan and serotonin production plays a detrimental role in mental health. 

L-Tryptophan Supplements For Cats & Dogs

Can dogs have L-tryptophan, or is tryptophan bad for dogs? L-tryptophan for cats and dogs is a popular supplement to treat behavior issues such as anxiety or aggression. Continue reading to learn more about how L-tryptophan can promote health benefits for pets, too! 


What is L-tryptophan for dogs used for? Does tryptophan make dogs sleepy? Does tryptophan affect cats, too?

L-tryptophan is used for domestic pets like cats and dogs to improve emotional well-being and reduce aggressive behavior. As L-tryptophan is connected to serotonin production, its supplementation benefits pets and promotes mood improvements. 

Research has elaborated on these benefits, presenting improvements in decreasing anxiety and stress-related behaviors. From the results, it is believed that L-tryptophan can be a productive part of pet behavior therapy. 

L-Tryptophan Uses For Pets:

  • Promotes sleep
  • Provide relief from anxiety
  • Reduces depression
  • Encourages emotional well-being 
  • Can improve pet’s behavior
A graph detailing how many people use l-tryptophan supplements for their pets.

Source: EverFlex Survey, 2024

Risks & Side Effects

Is L-tryptophan safe for dogs and cats? Well, like for humans, there are some risks associated with supplemental use of L-tryptophan. 

One of the main concerns is serotonin syndrome. To combat the likelihood of serotonin syndrome, consult your pet’s veterinarian about dietary changes, including L-tryptophan supplementation. 

Other L-tryptophan side effects to look out for include gastrointestinal upset, such as vomiting or diarrhea. Most pets will need time to get used to supplements, but taking your pet off L-tryptophan is recommended if the side effects are severe. 


Can you buy tryptophan?

Yes, tryptophan can be bought as a dietary supplement. There are different options for tryptophan supplements, such as capsules and powders. The dosages for supplements vary depending on the brand, including 500mg and 1000mg. 

How to find the best tryptophan supplement for sleep?

First, examine the brand’s reputation, reviews, and quality of ingredients to ensure that you are purchasing a product with a transparent and honest label. Some examples of high-quality tryptophan supplements include Double Wood’s 5-HTP and Onnit’s New Mood Instant powder packets

Can tryptophan cause anxiety?

Tryptophan supplementation is more often linked to a reduction of anxious feelings than the cause of anxiety. Taking antidepressant medications along with L-tryptophan supplements can result in a spiked production of serotonin, resulting in anxiety and heart problems

Does tryptophan help with eosinophilia-myalgia syndrome? 

No, it does not. The epidemic of eosinophilia-myalgia syndrome in 1989 was linked to manufactured L-tryptophan supplements. After investigative efforts, it was revealed that the cause of the epidemic was due to contamination of the L-tryptophan. 

Kaelyn Buzzo | ISSA CPT & Nutrition Coach

Kaelyn Buzzo | ISSA CPT & Nutrition Coach

I am an ISSA-certified CPT and Nutrition Coach with a BA in Creative Writing and a Minor in Nutrition.

Learn More About Kaelyn

More posts from Kaelyn Buzzo | ISSA CPT & Nutrition Coach

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