“L-tryptophan is an essential amino acid, which must be consumed from food since the body cannot make it using other amino acids. It is present in virtually all plant and animal proteins. Once the body absorbs L-tryptophan, it converts {some of}it into 5-hydroxytryptophan (5-HTP) and then into the neurotransmitter serotonin. It is primarily the serotonin that does all the wonderful things attributed to L-tryptophan—inducing sleep, reducing premenstrual syndrome (PMS) symptoms, promoting weight loss and addressing depression.” [1].  Additionally, L-tryptophan is necessary for the production of various protein structures in the body.

“Tryptophan is one of the eight essential amino acids found in the human diet. Essential amino acids are defined as those that cannot be made in the body and therefore must be obtained from food or supplements. (A ninth amino acid, histidine, is sometimes considered essential for children.)…

“A typical diet provides only 1,000 to 1,500 mg/day of tryptophan, yet there is much competition in the body for this scarce tryptophan” [2].

“In any normal diet, animal protein-based or vegetarian, tryptophan is the least plentiful of all 20 food amino acids. Thus, tryptophan is typically outnumbered as much as 9:1 in its competition to secure its transport through the blood-brain barrier into the brain. Eating a high-protein diet in an attempt to increase dietary tryptophan (a typical diet provides only 1-1.5 grams/day) only increases its competition even more” [3].

In the 1980s, “people seeking to lose weight, improve sleep, or alleviate depression used tryptophan to safely increase serotonin levels in the brain.  Serotonin is the natural compound that promotes feelings of well-being, satiety, and relaxation” [2].

Although there are animal source of tryptophan, Vegetarian Tryptophan is from plants and is 100% vegan. 

Mood & Tryptophan

L-tryptophan depletion seems to be a significant factor demonstrating the link between serotonin and mood. 

“Stress-related mood deterioration and affective disorders...are among the leading causes of disease burden throughout the world, and are associated with severe medical consequences and mortality. Research has shown the involvement of dysfunctional brain serotonin (5-HT) biochemistry as a vulnerable biological factor in the onset of mood disturbances. Since the production of brain serotonin is limited by the availability of its plasma dietary amino acid precursor tryptophan, different foods and dietary amino acids that influence tryptophan availability are thought to alter affective behavior by changing brain 5-HT synthesis” [4].   Serotonin is synthesized in the body from the amino acid tryptophan [5].

It tends to be accepted that impaired serotonin (5-HT) function can lead to mood problems [6], especialli in some women [7].

Those with other mood issues seem to have lower levels of serotonin [8].  A study involving those who were obsessive found that “[a]fter 5 h of tryptophan depletion, 6 out of 7 patients reported worsening of mood” [9].

Tryptophan depletion seems to increase issues like lack of proper emotional expression in some [10].  L-tryptophan supplementation has been found helpful to improve the mood of people with Hepatitis C [11].

A major study involving alcoholics trying L-tryptophan found that it helpful for moods [12]. 

Sleep

Many people have had success with sleep taking L-tryptophan for ocassional sleeplessness.  There are probably several reasons for this. 

“For example, serotonin is the precursor to the sleep hormone, melatonin, making L-tryptophan an effective sleep aid. It has significant sedative- like proper ties, although, unlike other sedatives, it does not appear to impair performance. Specifically, L-tryptophan is not associated with impairment of visuomotor, cognitive or memory performance, nor does it elevate threshold for arousal from sleep” [13].

“Melatonin is a hormone synthesized in the pineal gland from tryptophan. It participates in several biological processes in the human being, such as circadian sleep rhythm, mood, reproductive processes and aging” [14].

 “More than 40 controlled studies have demonstrated L-tryptophan can help induce sleepiness in humans... Generally, doses of 1 g/d or more are most effective.” [13].

One recent study found that taking L-tryptophan increased both serotonin and melatonin and improved nocturnal sleep [15].  Another recent study found for people who tened to be obsessive, “Tryptophan depletion induced a worsening of sleep continuity” [16].

Human Growth Hormone, Aging, Obesity, & L-Tryptophan

“For years, many people have been looking for ways to increase their levels of human growth hormone (HGH). The value of increasing HGH can be understood by examining this hormone’s functions, which include maintaining the immune system, stimulating muscle growth through amino acid sparing and promotion of amino acid transport into muscle cells, and burning fat. L-tryptophan is also capable of increasing HGH. This was demonstrated in various human studies in the ’70s.” [13].

“Startling research findings reveal that brain serotonin levels decline sharply in most humans as they age…It was long ago established that tryptophan is the amino acid needed to produce serotonin in the brain…Recent studies, however, have identified specific age-related mechanisms that cause the degradation of tryptophan in elderly individuals” [2].  Therefore, it appears that supplemental L-tryptophan could possibly be expected to reverse some of these losses of tryptophan and serotonin.

Some have indicated that L-tryptophan may be helpful for weight management and/or appetite control and/or other problems associated with low serotonin levels [e.g. 2,7,13,17].  “Plasma tryptophan ratios are below normal in obese subjects and may decrease with dieting, an effect that may partly be responsible for the high relapse rate after diet-related weight loss (ie, brain serotonin production remains low and stimulates appetite). Obese subjects are often insulin resistant, and diminished insulin action may cause low plasma tryptophan ratios because of the peripheral effects of insulin on amino acid uptake and utilization” [17].

“Serotonin neurons in the brain participate in the control of appetite. In general, serotonin neurons function in neuronal circuits that diminish food intake. Hence, treatments that enhance serotonin function reduce food intake, whereas those that diminish serotonin function stimulate food intake. The synthesis of serotonin in the brain is controlled in part by the availability of its amino acid precursor, L-tryptophan” [17].

Safety

There were some safety concerns about L-tryptophan that perhaps should be addressed here.  “In 1989 and 1990, two reports of a new disease labeled eosinophiliamyalgia syndrome (EMS) were published and attributed to ingestion of L-tryptophan… Studies traced more than 95 percent of the cases of EMS to L-tryptophan supplied by Showa Denko K.K. of Japan. Analysis of case-associated lots revealed several chemical impurities. One of these, labeled “peak E”, is an unusual dimeric form of L-tryptophan (1,1’-ethylidenebis[tryptophan]), and its presence is considered to be associated with EMS” [1]. 

The FDA, instead of initially simply placing the blame on the bad batch (or non-L-tryptophan causes for the EMS issues raised), restricted general supplementation with L-tryptophan.

However it needs to be emphasized “that the very tryptophan that the FDA restricted is still used in infant formulas and intravenous feeding solutions.  If there were any danger to tryptophan, we would have known about it long ago…For nineteen years, aging Americans have been forced to settle for less-than-optimal tryptophan/serotonin levels in their bodies” [2]—essentially because of unusual FDA restrictions.

It perhaps should be mentioned that an animal study designed to see if supplementation with relatively high levels of L-tryptophan could cause EMS concluded that it did not [18].

Notice the following comment from a study in the American Journal of Clinical Nutrition, “in our experience, pharmaceutical-grade tryptophan preparations in humans have never been associated with symptoms of EMS, suggesting that pure tryptophan preparations are safe” [19].

Here is what Ernest Hartmann (M.D.) of Tufts University wrote, “My laboratory has done many studies on the sleep inducing effects of tryptophan.  The usual human dose is either 1 or 2 g of tryptophan taken at bedtime…I do not believe that the totality of current evidence suggests that people using L-tryptophan in the usual doses for sleep induction need be concerned or need to discontinue the practice” [20].

Tryptophan is a component of proteins, and, as such, has been consumed for thousands of years.  It has been consumed in isolated forms for decades and is an essential amino acid.

Those interested in the potential benefits of L-tryptophan supplementation may wish to try Vegetarian Tryptophan.

Vegetarian Tryptophan Video

Nutrition from food, what a concept!

References                                          

[1] Bruno G. Revisting the Safety, Efficacy of L-Tryptophan: Part II.   April 2, 2007
[2]  Faloon W. The FDAs cruel hoax.  Life Extension.  2008 Apr:14(4):7-11
[3] Dean W, South J, English J.  5-HTP (5-Hydroxytryptophan) vs. Prozac (SSRIs). http://intelegen.com/nutrients/5htp_5hydroxytryptophan_vs.htm viewed 12/18/08
[4] Markus CR.  Dietary Amino Acids and Brain Serotonin Function; Implications for Stress-Related Affective Changes.  Neuromolecular Med. 2008;10(4):247-58
[5] Matthew D.  Proteins and Amino Acids.  In Modern Nutrition in Health and Disease, 10th edition.  Lippincott Williams & Wilkins, Phil., 2006: 23-61
[6] Cowen PJ.  Serotonin and depression: pathophysiological mechanism or marketing myth?  Trends Pharmacol Sci. 2008 Sep;29(9):433-6
[7] Smith KA, Williams C, Cowen PJ.  Impaired regulation of brain serotonin function during dieting in women recovered from depression.  Br J Psychiatry. 2000 Jan;176:72-5
[8] Wiste AK, Arango V, Ellis SP, Mann JJ, Underwood MD.  Norepinephrine and serotonin imbalance in the locus coeruleus in bipolar disorder.  Bipolar Disord. 2008 May;10(3):349-59
[9] Külz AK, Meinzer S, Kopasz M, Voderholzer U.  Effects of tryptophan depletion on cognitive functioning, obsessive-compulsive symptoms and mood in obsessive-compulsive disorder: preliminary results.  Neuropsychobiology. 2007;56(2-3):127-31
[10] Williams JH, Perrett DI, Waiter GD, Pechey S. Differential effects of tryptophan depletion on emotion processing according to face direction.  Soc Cogn Affect Neurosci. 2007 Dec;2(4):264-273
[11] Schaefer M, Winterer J, Sarkar R, Uebelhack R, Franke L, Heinz A, Friebe A. Three cases of successful tryptophan add-on or monotherapy of hepatitis C and IFNalpha-associated mood disorders.  Psychosomatics. 2008 Sep-Oct;49(5):442-6
[12] Asheychik R, Jackson T, Baker H, Ferraro R, Ashton T, Kilgore J.  The efficacy of L-tryptophan in the reduction of sleep disturbance and depressive state in alcoholic patients.  J Stud Alcohol. 1989 Nov;50(6):525-32
[13] Bruno G. Revisting the Safety, Efficacy of L-Tryptophan: Part II.   May 31, 2007
[14] Carranza-Lira S, García López F.  Melatonin and climactery.  Med Sci Monit. 2000 Nov-Dec;6(6):1209-12
[15] Paredes SD, Terrón MP, Cubero J, Valero V, Barriga C, Reiter RJ, Rodríguez AB.  Tryptophan increases nocturnal rest and affects melatonin and serotonin serum levels in old ringdove. Physiol Behav. 2007 Mar 16;90(4):576-82
[16] Voderholzer U, Riemann D, Huwig-Poppe C, Kuelz AK, Kordon A, Bruestle K, Berger M, Hohagen F.  Sleep in obsessive compulsive disorder: polysomnographic studies under baseline conditions and after experimentally induced serotonin deficiency.  Eur Arch Psychiatry Clin Neurosci. 2007 Apr;257(3):173-82
[17] Breum L, Rasmussen MH, Hilsted J, Fernstrom JD.  Twenty-four-hour plasma tryptophan concentrations and ratios are below normal in obese subjects and are not normalized by substantial weight reduction.  Am J Clin Nutr. 2003 May;77(5):1112-8
[18] Chung TK, Gelberg HB, Dorner JL, Baker DH. Safety of L-tryptophan for pigs.  J Anim Sci. 1991 Jul;69(7):2955-60
[19] Fernstrom JD.  Can nutrient supplements modify brain function?  Am J Clin Nutr. 2000 Jun;71(6 Suppl):1669S-75S
[20] Hartmann E.  Possible effects of tryptophan ingestion. J Nutr 117:1314, 1987