Carbohydrate intake improves cognitive performance of stress-prone individuals under controllable laboratory stress

Cognitive performance has been found to decline after exposure to stress, p articularly in stress-prone subjects. The present study investigated whethe r a carbohydrate-rich, protein-poor (CR/PP) diet, which may enhance cerebra l serotonin function in stress-prone subjects due to increases in the avail able tryptophan, improves the performance of stress-prone subjects after ex posure to acute laboratory stress. Twenty-two high-stress-prone (HS) subjec ts and twenty-one low-stress-prone (LS) subjects aged between 19 and 26 yea rs performed a memory scanning task after controllable and uncontrollable s tress, following either a CR/PP diet or a protein-rich, carbohydrate-poor ( PR/CP) isoenergetic diet. Uncontrollable stress reduced feelings of control (F(1,38) 9.30; P = 0.004), whereas pulse rate and skin conductance increas ed after both stress tasks (F(1,38) 78.34; P = 0.0005 and F(1,37) 83.16; P = 0.0004). Diet, stress-proneness and stress-controllability interacted (F( 1,36) 9.46; P = 0.004) in such a way that performance in HS subjects was be tter with the CR/PP diet than with the PR/CP diet, but only after controlla ble stress. As the CR/PP diet has been found to increase the plasma tryptop han:large neutral amino acids ratio, indicating an increased availability o f cerebral tryptophan and, thus, higher serotonin levels, it appears that t here may be an increased availability of brain serotonin in HS subjects aft er controllable laboratory stress.