The Importance of L-Tryptophan for Serotonin Production

The amino acid L-tryptophan is the primary precursor to serotonin. Serotonin, commonly referred to as the “happy molecule,” is a crucial neurotransmitter in regulating mood, behavior, and cognition.¹

Insufficient levels of serotonin are associated with discomfort, sleeplessness, depression, seasonal affective disorder, and chronic tiredness.¹ This critical neurotransmitter is responsible for:

• Maintaining nervous balance,
• Ensuring restful sleep,
• Promoting a positive mood and proper cognitive functions.²

For these reasons, the body requires an adequate supply of L-tryptophan to produce serotonin.¹

What is L-Tryptophan?

L-tryptophan, or simply tryptophan, is one of the eight essential amino acids. Essential amino acids cannot be synthesized in the human body and must be obtained from the diet.¹² Hopkins and Cole first discovered tryptophan in the early 1900s when they isolated it from casein protein. A few years later, Ellinger and Flamand identified its molecular structure.⁴

Tryptophan is necessary in very small amounts for overall nutrition, but the body has relatively poor storage for this amino acid, and its total content in the body is the lowest of all amino acids.³⁴ Good sources of tryptophan include oats, bananas, dried prunes, milk, tuna fish, cheese, bread, chicken, turkey, peanuts, and chocolate.

Mechanism of Action

Tryptophan improves brain health and function in a variety of ways. It’s especially noteworthy for its ability to enhance memory and boost serotonin. As a precursor to the neurotransmitter serotonin, tryptophan’s memory-enhancing properties are pivotal. Tryptophan intake also leads to a rise in other neurotransmitters such as melatonin and beta-endorphin.⁴
Studies suggest that tryptophan and serotonin play a crucial role in memory. Elevated brain serotonin in both animals and humans has been associated with enhanced cognitive capabilities. Depletion of tryptophan negatively impacts cognition by reducing serotonin levels. As a serotonin precursor, tryptophan significantly influences mood. Tryptophan supplementation not only enhances serotonin but also growth hormone and prolactin levels. Researchers have found that tryptophan significantly impacts mental and physical sedation but not tranquilization levels. At high doses, tryptophan provides a calming effect without inducing drowsiness.⁶

Understanding the Role of L-Tryptophan Supplements

L-Tryptophan is one of the essential amino acids that our bodies cannot produce, and therefore, it must be obtained from our diet. It plays a pivotal role in several physiological functions, primarily serving as a precursor for serotonin, a neurotransmitter crucial for mood regulation and sleep patterns. When dietary intake of L-Tryptophan isn’t enough, or when our bodies require more than usual due to stress or illness, supplementation can be considered. In the following section, we delve into the benefits and implications of L-Tryptophan supplementation on our body’s various systems.

Tryptophan Has a Positive Effect on Exercise Performance

Struggling to get through a training session even though you feel physically fine? Low tryptophan levels might be the problem. Given the amino acid’s role in serotonin production, tryptophan can impact your athletic performance.
In a study, the effects of L-tryptophan supplementation on sports performance were examined in 20 healthy men.⁷

Another study examined the effects of L-tryptophan supplementation on endurance and the sensation of effort.⁸ The average exercise time was nearly 50% higher in the trials where subjects took the supplements instead of a placebo. Researchers suggested that these findings might be due to improved pain tolerance as a result of L-tryptophan supplementation.⁴

Tryptophan Relieves Symptoms of Seasonal Affective Disorder

Seasonal Affective Disorder (SAD) is a form of depression that many individuals suffer from every winter. Symptoms include difficulty waking, diminished energy, weight gain, carbohydrate craving, trouble concentrating, decreased libido, restlessness, depression, and irritability. Light therapy is the typical treatment for SAD; however, many people do not respond well to this type of treatment due to a change in the quality of melanopsin and a disruption in the regular signaling pathway between the retina and the pineal gland.

In cases where light therapy is ineffective, supplementing with tryptophan to stimulate the production of serotonin and melatonin may be effective. Researchers at the University of British Columbia in Vancouver, Canada, set out to find out if tryptophan might assist those with seasonal SAD where light therapy did not work. The patients were treated for two weeks using light therapy. Those who did not respond to light therapy were treated with 1g of tryptophan three times a day for two weeks prior to light therapy. The inclusion of tryptophan resulted in significantly lower levels of depression. Sixty-four percent of the patients in this research reported very positive clinical responses to the combined therapy with minimal side effects.³

Recommended Dosage

There are several recommended dosage ranges for L-tryptophan. Your ideal intake will depend on the benefits you hope to reap. Let’s take a look:

• Better sleep, relaxation, and mental health – up to three grams (3,000 mg) daily (with up to a gram within an hour before bedtime);²

• Weight maintenance (and control of carbohydrate intake) – 8 mg tryptophan per kg of body weight;

• Athletic performance and pain tolerance – 600 mg of tryptophan supplement daily.¹⁰

1. Pardridge, William M., and William H. Oldendorf. 1975. “Kinetic Analysis of Blood-Brain Barrier Transport of Amino Acids.” Biochimica et Biophysica Acta (BBA) – Biomembranes 401 (1): 128–36. https://doi.org/10.1016/0005-2736(75)90347-8

2. Oldendorf, William H. 1977. “The Blood-Brain Barrier.” Experimental Eye Research 25 (January): 177–90. https://doi.org/10.1016/s0014-4835(77)80016-x

3. Matarese, Laura E., and Michele M. Gottschlich, eds. Contemporary Nutrition Support Practice: A Clinical Guide. 2nd ed. Philadelphia: Saunders, 2003

4. Sainio, E. -L., K. Pulkki, and S. N. Young. 1996. “L-Tryptophan: Biochemical, Nutritional and Pharmacological Aspects.” Amino Acids 10 (1): 21–47. https://doi.org/10.1007/bf00806091

5. Boer, Johan A. den, and Herman G.M. Westenberg. 1990. “Behavioral, Neuroendocrine, and Biochemical Effects of 5-Hydroxytryptophan Administration in Panic Disorder.” Psychiatry Research 31 (3): 267–78. https://doi.org/10.1016/0165-1781(90)90096-n

6. Winokur, Andrew, Nicholas D. Lindberg, Irwin Lucki, Jennifer Phillips, and Jay D. Amsterdam. 1986. “Hormonal and Behavioral Effects Associated with Intravenousl-Tryptophan Administration.” Psychopharmacology 88 (2): 213–19. https://doi.org/10.1007/bf00652243

7. Javierre, C., R. Segura, J. L. Ventura, A. Suárez, and J. M. Rosés. 2010. “L-Tryptophan Supplementation Can Decrease Fatigue Perception during an Aerobic Exercise with Supramaximal Intercalated Anaerobic Bouts in Young Healthy Men.” International Journal of Neuroscience 120 (5): 319–27. https://doi.org/10.3109/00207450903389404

8. Segura, R., and J. Ventura. 1988. “Effect of L-Tryptophan Supplementation on Exercise Performance.” International Journal of Sports Medicine 09 (05): 301–5. https://doi.org/10.1055/s-2007-1025027