“Every good act is charity. A man’s true wealth hereafter is the good that he does in this world to his fellow”, Molière once said. Or “When I do good, I feel good” as Abraham Lincoln put it.
And they were right, however, the amount of 'good' you do may just depend on what you had for breakfast (or dinner, or lunch).

Pharmacological studies in rats and humans suggest that the neurotransmitter serotonin plays a crucial role in promoting prosocial behavior. We therefore tested whether charitable donating, an important element of prosocial behavior, can be promoted by administering the food supplement L-Tryptophan (TRP), the biochemical precursor of serotonin. Thirty-two participants were compared with respect to the amount of money they donated when given the opportunity to make a charitable donation after the ingestion of either a placebo or TRP dissolved in orange juice. Of course, participants were not informed beforehand that the donating task was part of the experiment. The participants simply thought that they received money in reward for performing on a couple of tasks.

Donating behavior was measured by the amount of money the participant donated. After having received 10 Euros (one 5-Euronote, two 1-Eurocoins, and 6 Fifty cent-coins) for their participation in the study, participants were left alone and asked whether they were willing to donate part of their financial reward to charity. As expected TRP made participants donate significantly more money: Participants that ingested a neutral placebo donated 0,47 euro on average, whereas the participants that ingested TRP donated 1,00 euro.

Now, TRP is particularly plentiful in fish, eggs, soy and milk. And even though the exact mechanism may remain unclear, it does mean that we can increase prosocial behavior, and in particular trust (which you can read about in one of our previous blogs) and charitable donating, by promoting the intake of such foods. Hence, next time you are raising money for a charity – consider offering a glass of milk first.

Steenbergen, L., Sellaro, R., & Colzato, L.S. (2014). Tryptophan promotes charitable donating. Frontiers in Cognition, 5, 1451.