What is Tryptophan: Uses, Benefits, Foods, & Health Implications

Mix of colorful amino acids forming proteins

Looking for a nutrient that can boost your mood, improve your sleep, and keep your muscles in top shape? Meet tryptophan, the essential amino acid that does it all. 

So, what is tryptophan? As a critical building block for muscle and tissue, tryptophan is crucial for keeping your body strong. But that’s not all—it also acts as a precursor to serotonin, the “feel-good” neurotransmitter, and melatonin, the hormone that regulates sleep and circadian rhythms. Whether you get it from food or supplements, this versatile amino acid can significantly impact your overall health.

An Overview of the Essential Amino Acid Tryptophan

The amino acid tryptophan, found in the forms L-tryptophan or D-tryptophan, plays critical roles in metabolism and healthy physiological functioning. 

Because it is an essential amino acid (EAA), it can’t be produced naturally by the body and must be obtained from the diet. It’s known for synthesizing serotonin, a neurotransmitter critical for mood regulation, sleep, and appetite control. It’s also a precursor to several other vital biomolecules, including melatonin, which regulates sleep, and niacin, also known as vitamin B3.

What Does Tryptophan Do?

As an EAA, tryptophan is an amino acid and a crucial component for protein formation. Tryptophan combines with other amino acids in thousands of combinations to create essential molecules and tissues. Like other amino acids, tryptophan is commonly associated with its role in the structural makeup of muscle, but it also plays many other vital roles.

All amino acids, including tryptophan, help the body to:

  • Synthesize hormones
  • Generate neurotransmitters
  • Create enzymes
  • Build, maintain, and repair muscle
  • Grow and repair organs and connective tissue
  • Maintain healthy skin, hair, and nails

Tryptophan plays a crucial role in mood, sleep, and circadian rhythm by contributing to the production of melatonin and serotonin. After absorption, tryptophan is converted to 5-HTP and then to serotonin and melatonin, with the latter’s production in the pineal gland responsible for regulating the body’s circadian rhythm. While tryptophan intake is important, it’s not directly correlated with serotonin and melatonin synthesis, as the body has its own mechanisms to regulate these complex processes.

Serotonin

Hand holding a head

Tryptophan in the blood crosses the blood-brain barrier, becoming a precursor for serotonin synthesis, which affects mood, behavior, and cognition. Serotonin, produced mainly in the intestines, is linked to mood regulation, memory, and cognitive processes. 

Low serotonin levels are associated with depression and poor memory. While tryptophan intake can increase serotonin, other natural ways to boost serotonin include exercise, stress management, social connections, and a balanced diet.

Melatonin

Sleeper with dream-filled mind at rest

After serotonin is synthesized from tryptophan, the body can convert it to melatonin, a hormone that regulates sleep and circadian rhythm. Melatonin production is influenced by carbohydrate intake, tryptophan availability in the blood, and the ratio of tryptophan to other amino acids. 

While tryptophan intake can impact melatonin production, consuming more tryptophan-rich foods doesn’t necessarily lead to increased drowsiness.

Kynurenine

Tryptophan is broken down into kynurenine, which synthesizes niacin (vitamin B3). This process requires iron, vitamin B6, and vitamin B2. 

Exercise reduces tryptophan and kynurenine in sweat, suggesting an increased demand for muscle protein synthesis. This finding could affect exercise performance and rehabilitation routines, but factors like nutrition, exercise type, and individual characteristics influence it.

Benefits of Tryptophan

Tryptophan has essential functions and can provide additional benefits. Below, find out more about these benefits, from sleep to improving gut function! 

Sleep

a woman sleeping soundly

Tryptophan has been associated with improved sleep, notably through its relationship with serotonin and melatonin production. It has been used in the treatment of insomnia

One meta-analysis found that consuming more than one gram of tryptophan before bed may improve sleep quality. This study found that tryptophan supplementation reduced wakefulness after sleep onset (WASO). However, noticeable benefits have only been observed in individuals with low baseline serotonin levels and when tryptophan is taken as a supplement.

Irritable Bowel Syndrome (IBS)

Reduced tryptophan diets may benefit individuals with irritable bowel syndrome. 

One randomized control trial found that reducing tryptophan in combination with a low FODMAP diet significantly helped improve gastrointestinal symptoms more than a low FODMAP diet alone in individuals with diarrhea-predominant IBS. This intervention also improved mental health, specifically anxiety and depressive symptoms.

Anxiety

A tryptophan-depleted diet was found to decrease plasma tryptophan by 80 percent, which was associated with significantly increased anxiety and neurovegetative panic symptoms. While anxiety has many interrelated factors, this finding can help us understand some of the links between anxiety and diet.

Depression

Several studies have found an association between lower tryptophan levels in the blood and mood disorders like depression, and levels have been observed to improve with recovery. There is some evidence that tryptophan consumption may help reduce depressive symptoms compared to a placebo. Tryptophan has been studied in consideration as part of treatment for some psychiatric disorders.

Fibromyalgia

Consuming adequate tryptophan may help with the management of fibromyalgia symptoms. In particular, low tryptophan intake and absorption have been associated with increased fibromyalgia symptoms related to a lack of serotonin.

Exercise Recovery

Resting lady

Tryptophan consumption in the evening before sleep has been associated with decreased sleep latency. This is believed to be due to tryptophan’s impact on melatonin production. 

Improved sleep helps the body recover and prepare the energy needed for quality exercise performance and mental focus. Consuming adequate total protein and EAAs (like tryptophan) helps support optimal muscle protein synthesis. Exercise stimulates muscle protein synthesis and breakdown, so with adequate amino acid intake, including tryptophan, recovery and performance enhancements can be reaped. 

Other Uses

Tryptophan has also been used in the treatment of ADHD, chronic fatigue, premenstrual syndrome, bulimia, chronic pain, schizophrenia, and eating disorders.

The current research on the benefits of tryptophan isn’t entirely conclusive. There is no guarantee that everyone will respond similarly. Present evidence provides insight into the importance of tryptophan and how it can be used for our benefit.

How Much Do We Need?

Dietary tryptophan requirements vary depending on personal needs and goals. As with all essential nutrients, consuming too much or too little can have negative impacts.

You can improve tryptophan levels in the body by increasing tryptophan and carbohydrate intake. Most adults meet the recommended daily total protein intake, so taking tryptophan is also a sufficient method. Tryptophan recommendations are represented as grams of tryptophan per kilogram of total body weight per day.

  • Adults: The World Health Organization recommends a range of 2-5 mg/kg/day and narrows in on 4mg/kg/day as a target. This can also be represented at 6mg/g protein per day (assuming for maintenance, not muscle growth).
  • Pregnant or breastfeeding: Pregnant or breastfeeding individuals likely have higher tryptophan requirements due to increased total protein needs, but no official recommendations exist.
  • Tryptophan:lysine ratio: The recommended tryptophan: lysine ratio for adults is 0.13:1. This ratio likely isn’t relevant for the general population who consume a variety of protein-rich foods.

Tryptophan deficiency is uncommon and would be more likely to co-occur with total protein deficiency or protein-calorie malnutrition. 

Best Sources of Tryptophan

Plate with turkey, nuts, and tofu

Many foods contain tryptophan, notably protein-rich foods like meat and plant foods. If a food has any amount of protein, chances are it has at least some tryptophan. Foods have different proportions of amino acids, so some contain more tryptophan than others. Eating various protein-rich foods and emphasizing a balanced diet will help meet the needs for tryptophan and other amino acids.

FoodServing sizeTryptophan (g)Total protein (g)
Chicken breast, cooked (lean)3 oz0.3127
Turkey, cooked3 oz0.2624
Salmon, cooked3 oz0.2422
Tempeh100g0.1920
Edamame1 cup0.1918
Tofu, extra firm100g0.1813
Pumpkin seeds1/4 cup0.179
Egg1 large0.086
Oats, uncooked½ cup0.075

Figures are sourced from the USDA FoodData Central

Tryptophan Supplements

tryptophan supplements

In contrast to acute tryptophan depletion, supplementation studies suggest that increasing tryptophan levels can positively affect attention, memory, and mood. Supplements are available with tryptophan as the sole ingredient. EAA supplements and protein powders also contain tryptophan. 

Dietary supplements are not necessary to obtain adequate amounts of tryptophan. Eating foods rich in tryptophan also brings more opportunities for other beneficial micronutrients and phytochemicals.

Research suggests that tryptophan supplementation may have therapeutic indications for mood disorders such as major depressive disorder, seasonal affective disorder, and bipolar disorder. More evidence is required to determine more concrete recommendations for tryptophan treatments in clinical practice.

As with any dietary supplement, it’s important to be aware of amino acid supplements’ potential risks and side effects. Side effects of tryptophan supplements are uncommon and are mainly only observed at high doses. Consuming enough total protein and EAAs may be ideal compared to consuming more tryptophan through supplements.

Summary

Tryptophan synthesizes good health and can have additional benefits in specific populations. Tryptophan catabolism leads to synthesizing other vital biomolecules, including serotonin, melatonin, and niacin. Generally, if you’re consuming enough protein from various sources, you’re likely consuming enough tryptophan. It’s often recommended to meet dietary tryptophan intakes through foods rather than supplements, as foods also contain many other essential and beneficial nutrients. Don’t forget about the different amino acids—they’re all important.

Frequently Asked Questions

Which is better—tryptophan or 5-HTP?

Tryptophan is first converted to 5-HTP before it can be converted to serotonin. Because 5-HTP is one step further in this process, it may be considered more effective when seeking outcomes related to serotonin action.

Is tryptophan bad for your liver?

Tryptophan is generally considered safe for the liver in normal dietary amounts. However, high doses could have adverse effects, especially from supplements. It’s important to consider that excessive intake of any type of supplement can strain the liver, particularly if there are pre-existing liver conditions. Speak with your healthcare provider if you have concerns about tryptophan’s impact on your liver health.

Can I take tryptophan every day?

Ideally, tryptophan should be consumed daily as part of protein sources. Supplementation of tryptophan can be part of a daily intake for some individuals. Long-term daily tryptophan supplementation is not recommended without medical supervision.

Who should not take tryptophan?

Some individuals are at higher risk for adverse effects from tryptophan supplements. This includes those with liver disease. Individuals who are pregnant, breastfeeding, or taking antidepressants such as SSRIs or MAO inhibitors should check with their healthcare provider.

Avery Zenker | Registered Dietitian

Avery Zenker | Registered Dietitian

Avery is a Registered Dietitian with her Masters in Nutrition. Some of Avery’s areas of expertise include sports nutrition, plant-based eating, intuitive eating, disordered eating, digestion, weight loss, and balanced diet. Fitness has always been an important part of Avery’s lifestyle. Currently she enjoys a balanced routine of weightlifting, calisthenics, yoga, and various forms of cardio.

Learn More About Avery

More posts from Avery Zenker | Registered Dietitian

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