A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning

source extracted confidence: high 2026-04-09
#adult #affect #dietary-supplements #emotions #humans

A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning

Kikuchi et al., 2021 | J Diet Suppl | Systematic Review

Citation

Kikuchi Asako M, Tanabe Aya, Iwahori Yoshihiro. A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning. J Diet Suppl. 2021;18(3):316-333. doi:10.1080/19390211.2020.1746725

Abstract

L-tryptophan (TRP), one of the essential amino acids in humans, is a precursor of serotonin, and hence its intake is closely related to the suppression of depressed and anxious moods. We did a systematic review of RCTs to examine the effects of tryptophan intake on the mood of healthy adults by searching PubMed, the Cochrane Library, and Ichu-shi according to PRISMA guidelines. As a result, 11 RCTs met the criteria and were accepted. Four RCTs showed the effects of tryptophan intake on negative feelings and happy feelings in healthy individuals, with significant differences between the treatment and the control groups. This suggests that TRP intake may be an effective approach to decrease anxiety and increase positive mood in healthy individuals. On the other hand, the effectiveness of TRP for aggressive feelings was not recognized. Reviewing these 11 RCTs, we concluded that taking 0.14-3 g of TRP per day in addition to the usual meal can be expected to improve the mood of healthy individuals. In order to estimate the optimum amount of TRP intake more accurately, further studies need to be conducted with more appropriate settings of intake period, intake frequency, and intake method.

Key Findings

In order to estimate the optimum amount of TRP intake more accurately, further studies need to be conducted with more appropriate settings of intake period, intake frequency, and intake method.

Outcomes Measured

  • anxiety

Population

Field Value
Population healthy adults
Sample Size 11
Age Range See abstract
Condition anxiety

MeSH Terms

  • Adult
  • Affect
  • Dietary Supplements
  • Emotions
  • Humans
  • Randomized Controlled Trials as Topic
  • Serotonin
  • Tryptophan

Evidence Classification

  • Level: Systematic Review
  • Publication Types: Journal Article, Systematic Review
  • Vertical: tryptophan-sleep

Provenance

Source extracted via PubMed E-utilities API on 2026-04-09