A new study from Leiden University proves that the types of food we eat affect our trust levels.
The investigation was devised by a psychologist from Leiden University, Lorenza Colzato, and a team from the universities of Leiden and Münster.
The researchers looked at how people's trust levels were affected by eating foods that contain tryptophan. This is an amino acid present in eggs, fish, soya and spinach.
In the study, one group of participants was given ordinary orange juice, while the second group was given juice with added tryptophan. Neither group was aware of what they were drinking.
The participants then all played a simple "trust game," in which an individual's financial gain depended on their willingness to trust another's cooperation.
The Dutch scientists found that the subjects who had been given tryptophan-spiked juice were significantly more willing to trust the other person.
Colzato concluded that, "these results support the idea that 'we are what we eat': the food one eats has a bearing on one's state of mind."
Scientists have been aware for some time that tryptophan stimulates the production of serotonin, a hormone which alters our moods.
But no previous team had investigated whether tryptophan also positively affects our mental trust.
Colzato and her team's findings suggest that eating tryptophan-containing foods "may promote interpersonal trust in inexpensive, efficient and healthy ways."
The findings are an important achievement for the Leiden psychology department and will be published in the upcoming edition of Psychological Science.