Exploring L-Tryptophan for Sleep

L-tryptophan is an amino acid with a range of potential benefits. While it is usually possible to get enough of this nutrient from food, some people prefer to take a supplement. One of the most common reasons for doing this is to improve sleep. But is it effective?

This article explains the science behind L-tryptophan for sleep, how it works, and whether it is worth a try.

Does Tryptophan Help You Sleep?

Tryptophan is available in two forms, L-tryptophan and D-tryptophan. These molecules are mirror images of one another, and both exist naturally in food. However, most supplements contain L-tryptophan, and that is the focus of this article.

People take L-tryptophan supplements for various reasons, including mood disorders and insomnia, among many other conditions. This is because L-tryptophan acts as a precursor to two essential neurochemicals, serotonin and melatonin.


Serotonin has a vast range of functions within the body but is perhaps best known for its influence on mood. Meanwhile, melatonin is responsible for making us feel sleepy. Our brains produce it naturally in the evening in response to dimming light levels.

Because of its role in melatonin production, tryptophan is one of the most important amino acids for sleep. It also has a host of other essential functions in the body, including protein and vitamin B3 synthesis.

The recommended daily intake of tryptophan is 250–425mg. Most people get more than enough of this amino acid from their diets. Some especially L-tryptophan rich foods include:

  • Turkey
  • Chicken
  • Tuna
  • Milk
  • Cheese
  • Oats
  • Bread
  • Bananas
  • Dried prunes
  • Peanuts
  • Chocolate

However, tryptophan from food has to compete with many other amino acids to cross the blood-brain barrier. Therefore, people hoping to alleviate specific symptoms may choose a supplement to boost their consumption.

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So, just how effective is L-tryptophan when it comes to improving sleep? Here is some of the current research on the subject.

Research on L-Tryptophan as a Sleep Aid

Scientists conducted plenty of research on L-tryptophan sleep supplements throughout the 1970s and 80s, with promising results.

For example, a 1970 study for The Lancet investigated L-tryptophan’s effects on healthy subjects and those with insomnia.

Firstly, five healthy people took the amino acid for ten consecutive nights. The researchers found that they experienced increased non-rapid eye movement (NREM) and delta wave sleep. Delta wave, also known as stage IV sleep, is the deepest stage of sleep.

Next, seven people with insomnia took L-tryptophan for either five or ten consecutive nights. They experienced increases in NREM and total sleep time.

A 1986 study for European Neurology tested L-tryptophan on ten people with sleep disturbances. The participants’ issues included difficulty falling asleep and maintaining sleep. The researchers took sleep recordings over three nights.

On the first night, the participants did not receive any treatment, functioning as a baseline measure. On the second night, they used a saline solution and, on the third night, they took L-tryptophan.

On the third (L-tryptophan) night, the researchers observed that the subjects fell asleep more quickly. The treatment also appeared to influence the sleep period time and total sleep time. The participants also reported improvements in subjective feelings of sleepiness.

A more modern study from 2016 investigated L-tryptophan for people in recovery from drug dependence. The participants took the supplement or a placebo for two weeks. At the end of the fortnight, those who took L-tryptophan experienced significant improvements in sleep scores.

Reviews from 1982 and 1986 both support these results. They suggest that L-tryptophan enhances subjective sleepiness and reduces the length of time taken to fall asleep. A more recent 2016 review reported that L-tryptophan has “direct effects on sleep.” Its authors suggest it could also improve morning wakefulness and attention.

How to Take L-Tryptophan for Sleep

Regarding how to take tryptophan, there are a couple of different options.

Most supplements come in capsule form, providing a convenient way to take the amino acid.

Most supplements come in capsule form, providing a convenient way to take the amino acid. It is also possible to purchase L-tryptophan powder, which can be mixed into beverages. However, this option may be less suitable as a sleep aid since consumers may not wish to drink large quantities of liquid before bed.

L-Tryptophan Dosage for Sleep

There is no standard L-tryptophan dose for sleep. However, most of the current research suggests that doses of 1g or above are most effective.

A 1989 study for Sleep journal tested L-tryptophan doses of 1.2g and 2.4g on ten healthy volunteers. They found that both doses decreased the length of time taken to fall asleep. However, the higher dose appeared to have longer-lasting effects and produce more significant subjective sleepiness.


That said, the precise amount of L-tryptophan that an individual needs will depend upon various factors. They include age, overall health, and the severity of the condition. Therefore, it is advisable to seek medical advice before beginning supplementation to determine a safe and effective dosage.

It is essential not to take too much L-tryptophan as doing so could increase the risk of side effects. Some possible adverse reactions include:

  • Nausea
  • Vomiting
  • Heartburn
  • Abdominal pain
  • Diarrhea
  • Reduced appetite
  • Headaches
  • Light-headedness
  • Drowsiness
  • Dry mouth
  • Blurred vision
  • Muscle weakness
  • Sexual dysfunction

L-tryptophan can also interact with certain medications, including central nervous system depressants and some antidepressants. It is unsuitable for pregnant or breastfeeding women.

How Long Does It Take for L-Tryptophan to Work?

So, when is the best time to take tryptophan for sleep? A 2003 report suggests that approximately 45 minutes before bed may be optimal. Taking the supplement at this time allows the body to metabolize it by the end of the night. This ensures the consumer does not feel drowsy the following day.

Taking the supplement 45 minutes before bed allows the body to metabolize it by the end of the night.

People suffering from mild sleep disturbances may experience benefits after a single dose. However, those with more long-standing difficulties may require repeated use to notice an effect.

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