• Role in the Body: It acts as a precursor for serotonin (mood regulation) and melatonin (sleep cycle regulation), and helps synthesize proteins.
• Benefits: It is used to improve sleep (especially for mild insomnia), alleviate depression, reduce stress, and manage severe premenstrual syndrome (PMS).
• Foods High in Tryptophan: Turkey, chicken, dairy (milk, cheese), eggs, fish, peanuts, seeds, and oats.
• Side Effects: While generally safe, high doses may cause dizziness, nausea, and drowsiness. A major concern is serotonin syndrome—a potentially fatal condition characterized by fever, agitation, and muscle spasms—when taken with antidepressants (SSRIs, MAOIs).
• Dosage: The recommended daily allowance for adults is 250 mg to 425 mg, though typical dietary intake is around 900 to 1000 mg. [2]

Important Safety Warning: Individuals taking antidepressants, particularly SSRIs or MAOIs, should consult a doctor before using L-tryptophan supplements due to the risk of dangerous drug interactions. [2, 3, 4]

Information Gathered from Wikipedia:

Although is now available for purchase, there was a large tryptophan-related outbreak of eosinophilia-myalgia syndrome (EMS) in 1989. This outbreak caused 1,500 cases of permanent disability and at least thirty-seven deaths. Some studies traced the outbreak to L-tryptophan supplied by a Japanese manufacturer, Showa Denko KK. It was further hypothesized that one or more trace impurities produced during the manufacture of tryptophan may have been responsible for the EMS outbreak. The fact that the Showa Denko facility used genetically engineered bacteria to produce the L-tryptophan gave rise to speculation that the genetic engineering was responsible for such impurities. However, the methodology used in the initial epidemiological studies has been criticized. An alternative explanation for the 1989 EMS outbreak is that large doses of tryptophan produce metabolites which inhibit the normal degradation of histamine and excess histamine in turn has been proposed to cause EMS.

Most tryptophan was banned from sale in the US in 1991, and other countries followed suit. Tryptophan from one manufacturer, of six, continued to be sold for manufacture of baby formulas. At the time of the ban, the FDA did not know, or did not indicate, that EMS was caused by a contaminated batch, and yet, even when the contamination was discovered and the purification process fixed, the FDA maintained that L-tryptophan was unsafe. In February 2001, the FDA loosened the restrictions on marketing (though not on importation), but still expressed the following concern:

“Based on the scientific evidence that is available at the present time, we cannot determine with certainty that the occurrence of EMS in susceptible persons consuming L-tryptophan supplements derives from the content of L-tryptophan, an impurity contained in the L-tryptophan, or a combination of the two in association with other, as yet unknown, external factors.”