Evidence: Reasonable Possible Benefits: High Safety: High
TABLE OF CONTENTS
What is L-tryptophan?
Tryptophan is one of 9 essential amino acids. Our bodies cannot synthesize this amino acid but need it to survive. As a supplement, L-tryptophan is often used for improving sleep quality, mood, and cognition. This article is about the main benefits of L-tryptophan, its potential side effects, the best time to take it, and more.
What does L-tryptophan do for the body?
Tryptophan is an essential amino acid, which means the body needs it to survive and cannot synthesize it.
After you consume tryptophan, the body converts some of it to 5-HTP, which acts as a precursor to serotonin.
Serotonin can then convert into melatonin, which is why people often take tryptophan to enhance sleep quality.
The body can also make NAD+ molecules from tryptophan through a series of biological reactions. This pathway is most active in the morning when as much as 95% of tryptophan consumed is used directly for this purpose.
Possible benefits
It is important to note that all of the potential benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.
Major benefits
Correcting a tryptophan deficiency – Since L-tryptophan is an essential amino acid, the body needs at least some amount to survive and function properly. Not getting enough tryptophan can lead to multiple neuropsychological problems, such as depression, anxiety, irritability, impulsiveness, inability to concentrate, poor dream recall, and insomnia. Fortunately, a deficiency in this amino acid is rare and shouldn’t happen unless you consume too low amounts of protein.
Improved mood and well-being – The supplement supports emotional processing and healthy functional connectivity between the default mode network and emotion-related brain regions. This results in a calmer mood, improved well-being, and greater life satisfaction.
Improved social cognition – L-tryptophan has been shown by multiple studies to support prosocial interactions and increase people’s motivation to socialize. Those who take the supplements also tend to be more empathetic, charitable, and altruistic.
Minor benefits
Reduced appetite – The supplement is fairly effective at suppressing appetite and reducing food cravings. Those who tend to overeat as a coping mechanism tend to eat less when they take tryptophan.
Weight loss – This benefit is secondary to the reduction of appetite. If you take the supplement but eat the same amount of calories, it will not have a notable impact on your weight.
Improved sleep quality – 5-HTP, a byproduct of tryptophan, helps synthesize serotonin, which can turn into melatonin at night. Those who take the supplement often have deeper and more restorative sleep. One study has also found that taking L-tryptophan reduces sleep terrors. If you take the supplement to improve sleep quality, take it 30-60 minutes before bedtime.
Improved exercise performance – Multiple studies support that L-tryptophan is at least mildly effective at increasing power output and delaying time to exertion during exercise sessions.
Possible side effects
These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.
Drowsiness
Stomach pain
Nausea
Vomiting
Diarrhea
Blurry vision
Serotonin syndrome – Fortunately, this effect is uncommon and shouldn’t happen unless you take over 100 mg/kg of body weight or if you combine the supplement with SSRIs or SNRIs.
Amino acid imbalance – All essential and non-essential amino acids need to be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects without enough of another amino acid. That is most notably the case for glycine and methionine, but the principle applies to other amino acids, such as lysine and arginine, and the BCAA trio. Using a single amino acid supplement may lead to a negative nitrogen balance, which can lessen how well your metabolism works. A protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a specific amino acid/s.
Toxicity – While acute toxicity has never been reported, taking high amounts of L-tryptophan could lead to chronic toxicity over time and cause some health problems. To prevent chronic toxicity, it is best to stay below 2 grams a day unless you have a great reason to take more.
Contamination – Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, supplement companies can change their manufacturers without announcing it to the FDA.
Who should not take L-tryptophan?
You should probably avoid taking the supplement if you:
take SSRIs or SNRIs (the combination can lead to serotonin syndrome)
eat high amounts of protein from food (most whole foods contain at least some amount of each essential amino acid)
experience a severe adverse reaction after taking the amino acid
take 5-HTP (the effects would add up so it is wiser to only take one of these)
are on a tight supplement budget (since there are more cost-effective supplements on the market for most people)
Who will benefit the most?
You should consider taking the supplement if you:
consume very little protein (less than 0.3 grams/pound of body weight)
suffer from depression or generalized anxiety disorder
have insomnia or other sleep disorder
experience chronic pain
suffer from migraines
wish to reduce appetite and food cravings
How much L-tryptophan should you take?
The RDA (recommended daily allowance) for this amino acid is 5 mg/kg/day for all adult men and most adult women. This is enough for the majority of people to prevent any symptoms of deficiency.
The RDA increases to 7 and 9 mg/kg/day for pregnant and lactating women, respectively.
Since this amino acid is in almost every food, you probably already get sufficient amounts from food alone. About 0.36 grams of protein/pound of body weight should be enough to prevent a deficiency.
If you plan to take L-tryptophan as a supplement, 500-1000 mg/d appears to be the best daily target for most people. This amount should provide most of the benefits without meaningful side effects.
Some people may benefit from doses higher than 1000 mg/d. These include people with depression, chronic pain, migraines, and insomnia.
The upper safety limit for tryptophan is not well-established. To stay on the safe side, don’t take more than 2 grams daily unless you have a great reason to do so. Higher amounts may cause problems if you take the supplement for a prolonged period.
Food sources of L-tryptophan
Tryptophan is found in all whole foods that contain dietary protein.
The amount of L-tryptophan per gram of protein varies from food to food but a general rule of thumb is that the more protein you eat, the more tryptophan you are getting from food.
The easiest way to find out exactly how much L-tryptophan or other amino acids you are getting from food is with Cronometer.com. This free app allows you to track all vitamins, minerals, and more.
Best time to take L-tryptophan
Like most other amino acids, tryptophan is water-soluble, so you don’t have to take it with food to absorb it well. Taking the supplement with food is better if it causes stomach upset when you take it on an empty stomach.
To maximize cognitive and mood-enhancing benefits, take L-tryptophan in the morning. If your goal is to improve sleep quality, take the supplement 30-60 minutes before bedtime.
Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.
Interactions
Other amino acids All essential and non-essential amino acids need to be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects without enough of another amino acid. That is most notably the case for glycine and methionine, but the principle applies to other amino acids, such as lysine and arginine, and the BCAA trio. Using a single amino acid supplement may lead to a negative nitrogen balance, which can lessen how well your metabolism works. A protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a specific amino acid/s.
Serotonin-releasing drugs Most phenethylamines and amphetamines should never be combined with 5-HTP and L-tryptophan. The combination can lead to serotonin syndrome. The same applies to other classes of drugs and pharmaceuticals that release serotonin.
SSRIs Taking SSRIs together with 5-HTP or L-tryptophan may lead to serotonin syndrome. The same applies to some other groups of anti-depressants, such as SNRIs and tricyclic antidepressants (TCAs).
Sedatives 5-HTP and tryptophan often act as mild sedatives and can increase both the pleasant and unwanted effects of sedatives.
MAOIs The combination can cause acute serotonin syndrome in rats. Whether or not the same can happen in humans is not yet clear.
Where to buy L-tryptophan
Amazon is the best option for ordering L-tryptophan supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.
Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.
L-tryptophan vs. 5-HTP
L-tryptophan acts as a precursor to 5-HTP, which further converts into serotonin.
When you take tryptophan, the body gets to regulate how much 5-HTP to create from it. Taking 5-HTP overrides this regulatory process.
L-tryptophan is much safer in the long term. On the other hand, the effects of 5-HTP are usually more pronounced and do not seem to reach a plateau and diminishing returns at any dose.
Some of the tryptophan you take also goes to support other functions in the body, such as the creation of NAD+ molecules. This is especially the case if you take the supplement in the morning.
Unlike L-tryptophan, 5-HTP doesn’t directly improve exercise performance and power output. This effect is mostly due to increased NAD+ levels.
For most people, L-tryptophan is a better long-term strategy. It is wiser to choose this amino acid over 5-HTP unless you have a great reason to go for 5-HTP instead.
FAQ
While you can take the supplement daily, cycling off of it 2 days a week is likely a better strategy because it allows your body to stay sensitive to the supplement without developing notable tolerance.
All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes some time that can add up over months or years. The disadvantage of capsules is that they often contain bovine gelatin, which rarely comes from an ethical source.
Yes. If your goal is to enhance mood and cognition, taking this amino acid in the morning is superior. However, taking L-tryptophan before bed is better if you take it to improve sleep quality. L-tryptophan absorbs and digests well if you take it before falling asleep.
This amino acid should not become harmful once it exceeds the expiration date but can lose potency over time.
Keep the supplement in a cold, dark, and dry place, and it should remain just as potent for many months or even years.
While toxicity is rare, too much tryptophan in the system can cause some health problems, often related to too much serotonin in the system. It is best to stay below 2 grams a day to prevent these side effects.
You may need more of this amino acid if you: – eat very little protein (less than 0.3 grams/pound of body weight) – suffer from depression or generalized anxiety disorder – have insomnia or other sleep disorder – experience chronic pain – suffer from migraines – wish to reduce appetite and food cravings
L-tryptophan converts to serotonin very shortly after it enters the body.
You should notice the effects about an hour after you take the supplement.
Amino acid supplements often come from animal products, but they do not have to be since all whole plant foods contain all essential amino acids. You can easily find vegan-friendly L-tryptophan powders but always check the label to be sure. If you buy the amino acid in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.
Like most other amino acids, tryptophan is water-soluble, so you don’t have to take it with food to absorb it well.
While low doses may not break a fast, higher doses certainly can. If you practice time-restricted eating, take this amino acid during your eating window so it doesn’t break your fast.
References
Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything said in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.
