(Source: SaluGenecists, Inc.)

Tryptophan is one of the 10 essential amino acids that the body uses to manufacture new proteins. Essential amino acids are those that are not synthesized in the body and need to be consumed through the diet.

Tryptophan may be familiar to many people as the purported cause of the post-Thanksgiving Dinner nap. While the cause of that sleepy feeling is probably multifactorial, turkey does contain a concentrated amount of tryptophan, which is believed, under certain circumstances, to produce a sense of drowsiness and relaxation.


Physiological effects of tryptophan

  • Helps regulate appetite
  • Promotes better sleep quality
  • Elevates mood

Physiological events that may signal a need for greater tryptophan intake

  • Anxiety
  • Depression
  • Irritability
  • Impatience
  • Impulsiveness
  • Inability to concentrate
  • Poor dream recall
  • Insomnia
  • Weight gain or unexplained weight loss
  • Overeating and/or carbohydrate cravings
  • Slow growth in children



Functions of tryptophan

Prevention of niacin deficiency

One of tryptophans important functions is to serve as building block for vitamin B3. Approximately 3% of our dietary tryptophan is converted into this important vitamin. This helps to guard against vitamin B3 deficiency, especially in times when intake of this vitamin is inadequate.

Enhancing serotonin levels

The other main function of tryptophan is as a precursor for serotonin, the neurotransmitter that helps to regulate mood, sleep patterns and appetite. Given its ability to increase serotonin levels, therapeutic tryptophan administration has been used in the treatment of a variety of neuropsychological conditions, including depression, insomnia and anxiety.

Deficiency Factors

Causes and symptoms of tryptophan deficiency

Inadequate dietary protein intake can contribute to a deficiency of tryptophan.

Other factors can impact its conversion to serotonin. These include low levels of dietary vitamin B6, high sugar intake, excessive consumption of alcohol, cigarette smoking, hypoglycemia and diabetes. Additionally, since the tryptophan to serotonin conversion necessitates a very fine equilibrium between a variety of factors, excessive protein intake can also be an inhibiting factor. In addition, vitamin B6 deficiency can impair its conversion to niacin since it is a necessary cofactor in this reaction.

Since it is an essential amino acid, tryptophan deficiency may cause symptoms mirror those of protein deficiency. These include weight loss and impaired growth in infants and children.

As insufficient dietary intake of tryptophan can lead to low serotonin levels, deficiency can lead to neuropsychological symptoms including depression, anxiety, irritability, impulsiveness, inability to concentrate, poor dream recall and insomnia. Other associated symptoms include carbohydrate cravings, overeating and weight gain.

If there is a concomitant dietary niacin deficiency, insufficient dietary tryptophan can also result in pellagra, which is the classical niacin deficiency disease. This condition, which is very rare in the United States, is characterized by the 4 Ds dermatitis, diarrhea, dementia and death.

Toxicity Factors

Causes and symptoms of tryptophan toxicity

Tryptophan supplements have been administered therapeutically, as either a dietary supplement or prescription medication, in dosages exceeding 5 grams per day with no report of adverse events. In addition, high dietary tryptophan from food has not been found to cause any toxicity symptoms.

Yet since 1989 tryptophan supplements are no longer available as a dietary supplement in the United States due to the Food and Drug Administrations perspective that high doses of tryptophan are categorically unsafe. Their perspective reflects events that occurred in 1989 when the use of tryptophan-containing dietary supplements was held responsible for the development of a serious condition known as eosinophilia-myalgia syndrome (EMS). Over one thousand people developed EMS with more than 30 deaths attributed to it. Upon investigation, a contaminant was found in one batch of the tryptophan sold by one manufacturer and occurred in only a small number of susceptible individuals. Yet, the FDA still holds that tryptophan is unsafe and therefore disallows it to be sold as a dietary supplement.

The Institute of Medicine at the National Academy of Sciences has yet to establish a Tolerable Upper Intake Level (UL) for tryptophan.

Cooking, Storage and Processing

Effects of cooking, storage and processing on tryptophan

There is currently no scientific literature showing problematic effects of cooking, storage, or processing on tryptophan levels in food.

Drug & Nutrient Interactions

Interactions between medications and tryptophan

Individuals who take Prozac, Paxil, Zoloft or other antidepressant medications classified as serotonin reuptake inhibitors (SSRIs) should consult with a physician before taking any other supplement, such as tryptophan, that also increases the amount of, or the effect of, serotonin in the body.

Nutrient Interactions

Interactions that occur between tryptophan and other nutrients

The amino acids tyrosine and phenylalanine compete for absorption with tryptophan. This is why some health care practitioners believe that food sources of tryptophan, because they are also sources of these other amino acids, do not cause a significant increase in the tryptophan levels to produce therapeutic results. Therefore, they suggest that only tryptophan taken in supplemental form can achieve these therapeutic levels.

Tryptophan requires vitamin B6, vitamin C, folic acid and magnesium for its metabolism.

Health Conditions

Health conditions require special emphasis on tryptophan

Individuals who have the following health conditions should pay special attention to their tryptophan status:

  • Anxiety
  • Depression
  • Headaches
  • Insomnia
  • Nightmares
  • Obesity
  • Obsessive/compulsive disorder
  • Pain
  • Premenstrual syndrome
  • Senile dementia
  • Tourette\'s syndrome

Forms in Dietary Supplements

Forms in which tryptophan is found in dietary supplements.

Until 1989, tryptophan supplementation was standard practice in many countries around the world - including the United States - to treat insomnia, depression, and anxiety.

In the summer and fall of 1989, hundreds of people taking tryptophan supplements in the U.S. began to report the development of serious side effects including muscle and joint pain, high fever, weakness, swelling of the arms and legs, and shortness of breath, a constellation of symptoms that later became known as eosiniphilia-myalgia syndrome (EMS).

Upon investigation, it was discovered that nearly all of the cases of EMS could be traced back to a contaminant found in one batch of tryptophan produced by a Japanese manufacturer called Showa Denko K.K. While all manufacturers of supplemental tryptophan synthesized this amino acid through a fermentation process using bacteria, several months before the outbreak of EMS, Showa Denko K.K. had altered its process to make it more efficient and was apparently unaware that a toxic contaminant was being produced.

The United States Food and Drug Administration took immediate steps to limit the availability of tryptophan, and since 1989 this amino acid has not been sold as a dietary supplement. Tryptophan is still available, however, for use in the manufacture of infant formulas and enteral and parenteral (intravenous) nutritional supplements prescribed by physicians.

A few years ago, a new tryptophan-like supplement emerged in the U.S. marketplace. This supplement is called 5-hydroxytryptophan or 5-HTP. 5-HTP has been used in much the same way as tryptophan for the treatment of depression and insomnia, and for weight loss. The reason is simple: the body ordinarily takes tryptophan and converts it into 5-HTP, and then takes the 5-HTP and converts it into serotonin. By taking 5-HTP, a person is taking a compound that is actually one step closer to serotonin than tryptophan.

Food Sources

Foods that are concentrated sources of tryptophan

Although tryptophan does occur naturally in nearly all foods that contain protein, it does so in smaller amounts compared to the other essential amino acids. Foods that are notable sources of tryptophan include bananas, dairy products, nuts, red meat, seeds, shellfish, soybeans and soy products, tuna and turkey.