Prenatal stress may increase the risk for depression in offspring and it has been suggested that this could be linked to alterations in tryptophan metabolism, leading to serotonergic changes. Dietary patterns based on the Mediterranean (Med) diet, which includes foods rich in nutrients involved in the tryptophan-serotonin pathway, have been linked to depressive symptom improvements when used as an intervention. This thesis examined, in a mouse model, whether a Med-based diet normalized depressive-like behaviour and changes in the serotonin system in the colon and hippocampus resulting from a repeated physical restraint stressor administered during the second trimester in adult C57BL/6N female and male offspring. The Med-based diet modulated behaviour and hippocampal serotonin receptors primarily in females and changed the enzyme involved in the colonic serotonergic pathway in males. These results suggest that a Med-based diet may help improve behavioural disturbances stemming from prenatal stress in a sex-specific way, perhaps through its actions on the gut-brain serotonin system.