Kan ett tillskott av tryptofan ha en inverkan på  sjukdomstillstånd som depression och/eller smärta?

Sammanfattning: 5-hydroxytryptamin (5-HT) is biochemically derived from Tryptophan. Kynurenic acid and quinolinic acid are also known metabolites of tryptophan. 5-HT is considered to play a role in depression and today selective serotonin reuptake inhibitors (SSRIs) are used for treatment of depression. 5-HT may also play a role in pain perception. The aim of this study was to investigate whether a supplement of tryptophan may affect conditions such as depression and/or pain. Reviewed studies show that tryptophan deficiency leads to less availability of tryptophan in the brain, which reduces the synthesis of serotonin. Lowering of mood appears and seems to be linked to the decrease in serotonin synthesis. Supplements of tryptophan have in some studies been shown to have effects on social behaviour with reduced quarrelsome behaviour and increased dominant behaviour. Corresponding studies on the effects on pain provide a complex picture. Results indicate that in acute pain 5- HT seems to provide some pain relief but contradictory responses to 5-HT are seen in neuropathic and inflammatory pain. Comorbidity with both depression and pain occur, and has been linked to the increase in tryptophan metabolism through the kynurenine pathway. Enzymatic modifications have been detected which lead to elevated kynurenine/tryptophan ratios. This seems relevant to this comorbidity. Tryptophan as a supplement for effects on conditions such as depression and/or pain is very uncertain because of the complexity in physiological responses. More studies are needed.