:Tryptophan:

Function: Sleep promoter

Tryptophan is an essential amino acid which is the precursor of serotonin. Serotonin is a brain neurotransmitter, platelet clotting factor and neurohormone found in organs throughout the body. Metabolism of tryptophan to serotonin requires nutrients such as vitamin B6, niacin and glutathione. Niacin is an important metabolite of tryptophan. High corn or other tryptophan-deficient diets can cause pellagra, which is a niacin-tryptophan deficiency disease with symptoms of dermatitis, diarrhea and dementia.

Inborn errors of tryptophan metabolism exist where a tumor (carcinoid) makes excess serotonin. Hartnup's disease is a disease where tryptophan and other amino acids are not absorbed properly. Tryptophan supplements may be useful in each condition, in carcinoid replacing the over-metabolized nutrient and in Hartnup's supplementing a malabsorbed nutrient. Some disorders of excess tryptophan in the blood may contribute to mental retardation.

Assessment of tryptophan deficiency is done through studying excretion of tryptophan metabolites in the urine or blood. Blood may be the most sensitive test because the amino acid tryptophan is transported in a unique way. Increased urination of tryptophan fragments correlates with increased tryptophan degradation, which occurs with oral contraception, depression, mental retardation, hypertension and anxiety states.

The requirement for tryptophan and protein decreases with age. Adults' minimum daily requirement is 3 mg/kg/day or about 200 mg a day. This may be an underestimation, for there are 400 mg of tryptophan in just a cup of wheat germ. A cup of low fat cottage cheese contains 300 mg of tryptophan and chicken and turkey contain up to 600 mg per pound.
Tryptophan supplements of up to 3 g a day have been used to control intractable pain in various conditions. Furthermore, tryptophan supplements decrease aggressive behavior. Abnormalities in tryptophan metabolism occur in aggressive mentally retarded patients. Increased violent crimes occur in areas where tryptophan-deficient corn is a major dietary staple. Vitamin B6 and tryptophan supplements can correct some of the biochemical disorders related to aggression. Drugs which increase the opposite neurotransmitter, dopamine-i.e., Nardil or bromocriptine---can produce rage reactions, as do drugs which inhibit vitamin B6, i.e., isoniazid, which inhibits metabolism of tryptophan to niacin.

Tryptophan is also a useful treatment for insomnia; significantly reducing the time needed to fall asleep. Effective doses range from 500 to 2000 mg. Disorders of REM sleep may require doses of 3 to 15 g.

Suicidal patients show a significant decrease in serotonin levels. These patients, as well as agitated, depressed patients, do well with tryptophan supplements. Most antidepressants prolong the effects of serotonin by preventing reuptake of this neurotransmitter, as well as the reuptake of catecholamine; Tryptophan at night and tyrosine in the morning can probably mimic the effects of most antidepressants. Levels of the neurotransmitters are directly dependent on dietary tryptophan and other amino acids.

Tryptophan has many other reported desirable effects. Appetite for carbohydrates is decreased and blood sugar is raised by tryptophan supplements. It stimulates growth hormone and prolactin, which is the basis of some of tryptophan I s therapeutic effects.

Tryptophan is also beneficial in some forms of schizophrenia; it probably acts by balancing dopamine excess. In Parkinson's it inhibits tremor, and possibly also in progressive myoclonic epilepsy. Patients with kidney failure, on birth control pills, or with Down's syndrome may need more tryptophan.

Chronic tryptophan supplementation (minimum 2 g daily), like supplementation with other amino acids, raises many plasma amino acids besides tryptophan itself. This is positive and exciting because many amino acids tend to decrease with age.