Effect of meal composition on alertness and performance of hospital night-shift workers. Do mood and performance have...

We have studied the effect of diet composition on performance during, and after night-shift work. On three occasions 21 night workers at the Hadassah University Hospital, Jerusalem ate one of three meal plans--a diet enriched with protein (PROT 52%), carbohydrate (CHO 70%) or their regular (REG) diet (PROT 18%, CHO 55%); fat composition was held constant (ca. 27%). Outcome measures were subjective alertness, psychometric performance, and plasma concentrations of glucose, insulin and amino acids. Insulin and glucose levels were similar after the different diets. There were no clear relationships between tyrosine and tryptophan ratios and performance. However, within PROT diet, differences in psychometric performance correlated with glucose (p = 0.05) and insulin concentrations (p = 0.04), and the tyrosine:large neutral amino acid ratio correlated with alertness (p = 0.05). After the CHO diet, glucose concentrations related to sleepiness (p = 0.035). In this population, self-selected for night-shift work, there were no clear-cut differences in subjective feelings or objective performance between the different diets. The preferred regular diet gave the best performance and had a metabolic profile similar to the CHO diet. This suggests that a CHO:PROT ratio of around 3.0 might give the optimal balance between mood and performance during night-shift work.