Everyone knows that a good night's sleep prepares you for the day.

In addition, several nutrients promote good sleep quality and support your mood.

Tryptophan , an amino acid found in many foods and supplements, is one of them.

It is necessary for making proteins and other important molecules in your body, including those necessary for optimal sleep and mood.

This article describes the effects of tryptophan on these fundamental areas of your life.

Tryptophan is one of many amino acids found in protein foods.

In your body, amino acids are used to make proteins but also serve other functions ( 1 ).

For example, they are necessary to produce several important molecules that support signal transmission.

Specifically, tryptophan can be converted into a molecule called 5-HTP (5-hydroxytryptophan), which is used to produce serotonin and melatonin ( 2 , 3 ).

Serotonin affects multiple organs, including the brain and gut. In the brain, it specifically influences sleep, perception and mood ( 4 , 5 ).

Meanwhile, melatonin is a hormone that is primarily involved in your sleep-wake cycle ( 6 ).

Overall, tryptophan and the molecules it produces are essential for your body to function optimally.

Several studies have shown that lower than normal levels of tryptophan can occur in depression ( 7 , 8 ).

Other research has examined the effects of altering tryptophan in the blood.

By lowering tryptophan levels, researchers can learn about their functions. To do this, the study participants ingest large amounts of amino acids with or without tryptophan ( 9 ).

In one such study, 15 healthy adults were exposed to a stressful environment twice - once when tryptophan blood levels were normal and once when levels were low ( 10 ).

The researchers found that anxiety, tension and nervousness were higher when participants had low levels of tryptophan.

Based on these results, low tryptophan concentrations could contribute to anxiety ( 11 ).

They can also increase aggression and impulsivity in aggressive individuals ( 12 ).

On the other hand, taking tryptophan can promote good social behavior ( 13 ).

Altering tryptophan can affect various aspects of cognition.

One study found that long-term memory performance was worse when tryptophan levels were reduced than when levels were normal ( 14 ).

These effects were observed regardless of whether participants had a family history of depression.

A large study also found that lower levels of tryptophan negatively affected cognition and memory ( 15 ).

Memory associated with events and experiences may be particularly impaired.

These effects are likely due to the fact that as tryptophan levels decrease, serotonin production decreases ( 15 ).

Tryptophan can be converted in the body into the molecule 5-HTP, which then forms serotonin ( 14 , 16 ).

Based on numerous experiments, researchers agree that many of the effects of high or low tryptophan levels are due to serotonin or 5-HTP ( 15 ).

In other words, increasing levels can lead to increased 5-HTP and serotonin ( 17 , 18 ).

Serotonin and 5-HTP affect many processes in the brain, and disruptions to their normal actions can influence depression and anxiety ( 5 ).

In fact, many medications used to treat depression modify the effects of serotonin in the brain to increase its activity ( 19 ).

In addition, serotonin influences the learning processes in the brain ( 20 ).

Treatment with 5-HTP may also help increase serotonin and improve mood and panic, as well as insomnia ( 5 , 21 ).

Overall, the conversion of tryptophan to serotonin is responsible for many of its observed effects on mood and cognition ( 15 ).

Once serotonin is produced from tryptophan in the body, it can be converted into another important molecule - melatonin .

In fact, research has shown that increasing tryptophan in the blood directly increases both serotonin and melatonin ( 17 ).

In addition to being naturally present in the body, melatonin is also a popular dietary supplement found in various foods such as tomatoes, strawberries, and grapes ( 22 ).

Melatonin influences the body's sleep-wake cycle. This cycle affects many other functions, including the metabolism of nutrients and your immune system ( 23 ).

Several studies have shown that increasing tryptophan in the diet can improve sleep by increasing melatonin ( 24 , 25 ).

One study found that eating tryptophan-enriched cereal for breakfast and dinner helped adults fall asleep and sleep longer compared to standard cereal ( 25 ).

Anxiety and depression symptoms were also reduced, and it is likely that tryptophan contributed to the increase in serotonin and melatonin.

Other studies have also shown that taking melatonin can improve the amount and quality of sleep ( 26 , 27 ).

Many different protein foods are good sources of tryptophan ( 28 ).

For this reason, you ingest some tryptophan every time you eat protein-rich foods.

Your intake depends on how much protein you consume and what protein sources you consume.

Some foods are particularly high in tryptophan, including poultry, shrimp, eggs, and crabs ( 28 ).

It has been estimated that a typical diet provides approximately 1 gram per day ( 29 ).

You can also supplement with tryptophan or one of the molecules it produces, such as 5-HTP and melatonin.

Because tryptophan is an amino acid found in many foods, it is believed to be safe in normal amounts.

It is estimated that a typical diet contains 1 gram per day, but some individuals opt for a dosage of up to 5 grams per day ( 29 ).

Its possible side effects have been studied for over 50 years and very few of them have been reported.

However, side effects such as nausea and dizziness have occasionally been reported at doses above 50 mg per kilogram of body weight, or 3.4 grams in a 68 kg adult ( 29 ).

Side effects may be more pronounced when tryptophan or 5-HTP is taken with medications that affect serotonin levels, such as antidepressants.

When the activity of serotonin is excessively increased, it can lead to a condition called serotonin syndrome ( 33 ).

It can cause various symptoms including sweating, tremors, agitation, and delirium ( 29 ).

If you are taking medications that affect your serotonin levels, you should consult your doctor before taking tryptophan or 5-HTP supplements.

Your body uses tryptophan to make several important molecules, including serotonin and melatonin.

Serotonin influences your mood, your cognition and your behavior , while melatonin influences your sleep-wake cycle.

Therefore, low tryptophan levels can lower serotonin and melatonin levels, which has detrimental effects.

Although tryptophan is found in protein foods, it is often taken as a supplement. It is probably safe in moderate doses. However, side effects may occasionally occur.

These side effects may become more serious if you are also taking medicines that affect your serotonin levels, such as antidepressants.

Some of the molecules that tryptophan produces in the body, including melatonin, are also sold as supplements.

Overall, tryptophan is a crucial amino acid for your health and well-being. Certain people may benefit from increased intake of this amino acid or the molecules it produces.