It's easier to say 'no' when you take an L-tryptophan supplement

Study

Dutch psychologists at the University of Leiden gave two dozen participants a supplement containing L-tryptophan, morning, noon and evening for six days. Each participant took a total of 2.8 g L-tryptophan per day. A comparable group took a placebo.

After the supplementation period the participants played the Ultimatum Game. [Ask Google]. In the game the participants were given an offer of sharing a sum of money by an opponent. On one occasion the participants were offered 45 percent of the money [Fair], on another occasion 32 percent [Not fair] and on yet another occasion 21 percent [Not fair at all]. The opponent would only get that amount of money from the researchers if the participants agreed to share the sum of money.

Results

Supplementation with L-tryptophan reduced the likelihood of the participants going along with unfair offers.

Explanation







"Acute tryptophan depletion was associated with a higher rejection rate [Science. 2008 Jun 27;320(5884):1739.] of very unfair offers than sham acute tryptophan depletion in healthy individuals," the researchers wrote. "In healthy participants, a single dose of the selective serotonin reuptake inhibitor citalopram (30 mg) was associated with a lower rejection rate of unfair offers [Proc Natl Acad Sci U S A. 2010 Oct 5;107(40):17433-8.] than placebo."

"In another study, [Neurosci Lett. 2008 May 30;437(2):158-61.] healthy students who tended to reject unfair offers had lower platelet serotonin content than participants who tended to accept the offers. Finally, a PET study [Proc Natl Acad Sci U S A. 2012 Mar 13;109(11):4281-4.] in 20 healthy males showed that individuals with low levels of 5-HT transporter binding in the dorsal raphe nucleus were more likely to reject unfair offers."

Conclusion

"Our study shows that increasing serotonin through prolonged tryptophan supplements increases the rejection of very unfair offers in healthy volunteers," the researchers summarised. "If replicated, this implies that a prolonged increase of serotonin availability affects social decision-making differently than acute enhancement of serotonin availability."

Source:

Front Psychol. 2015 Jul 16;6:1012.

More:

5-HTP - supplementation for a broken heart 30.01.2013

L-Tryptophan gives women a rosy view of the world 19.05.2009



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