Using a randomized crossover study design, 25 healthy young adults were examined for differences in anxiety, depression, and mood after consuming a high tryptophan and a low tryptophan diet for four days each. There was a two week washout between the diets. A within-subjects analysis of the participants’ mood indicated significantly (p < .01) more positive affect scores after consuming a high tryptophan diet as compared to a low tryptophan diet. Negative affect differences between the diets were not statistically significant (p > .05). Also, consuming more dietary tryptophan resulted in (p < .05) less depressive symptoms and decreased anxiety.

The objective of this study was to examine the effect of fluid intake and possible dehydration on cognitive flight performance of pilots. A repeated-measures, counterbalanced, mixed study design was used to examine differences in working memory, spatial orientation, and cognitive flight performance of 40 randomly selected healthy pilots after having high and low fluid intakes. Serial weights were also analyzed to determine differences in cognitive flight performance of the dehydrated (1-3% weight loss) and hydrated study participants. Results showed flight performance and spatial cognition test scores were significantly (p < 0.05) poorer for pilots who had low fluid intakes and experienced dehydration in comparison to the hydrated pilots. These findings indicate fluid intake differences resulting in dehydration may have safety implications because peak cognitive performance among pilots is critical for flight safety.