British Journal of Nutrition

Research Article

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

C. R. Markusa1 c1, G. Panhuysena1, L. M. Jonkmana1 and M. Bachmana1

a1 Department of Psychonomics, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands

Abstract

Cognitive performance has been found to decline after exposure to stress, particularly in stress-prone subjects. The present study investigated whether a carbohydrate-rich, protein-poor (CR/PP) diet, which may enhance cerebral serotonin function in stress-prone subjects due to increases in the available tryptophan, improves the performance of stress-prone subjects after exposure to acute laboratory stress. Twenty-two high-stress-prone (HS) subjects and twenty-one low-stress-prone (LS) subjects aged between 19 and 26 years performed a memory scanning task after controllable and uncontrollable stress, 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 increased 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 better with the CR/PP diet than with the PR/CP diet, but only after controllable stress. As the CR/PP diet has been found to increase the plasma tryptophan: large neutral amino acids ratio, indicating an increased availability of cerebral tryptophan and, thus, higher serotonin levels, it appears that there may be an increased availability of brain serotonin in HS subjects after controllable laboratory stress.

(Received October 01 1998)

(Revised June 04 1999)

(Accepted June 24 1999)

Correspondence:

c1 *Corresponding author: Dr Rob Markus, present address TNO Nutrition and Food Research Institute, Division of Target Organ Toxicology, Utrechtseweg 48, PO Box 360, 3700 AJ Zeist, The Netherlands, fax +31 30 6960264, email Markus@voeding.tno.nl

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