Appetite, 1998, 31, 49–65 Article No. ap970155 Does Carbohydrate-rich, Protein-poor Food Prevent a Deterioration of Mood and Cognitive Performance of Stress-prone Subjects when Subjected to a Stressful Task? C. R. MARKUS, G. PANHUYSEN and A. TUITEN Department of Psychonomics, Utrecht University, The Netherlands H. KOPPESCHAAR Department of Endocrinology, University Hospital Utrecht, The Netherlands D. FEKKES Section Pathophysiology of Behaviour, Erasmus University, The Netherlands M. L. PETERS Department of Clinical and Health Psychology, Utrecht University, The Netherlands This study investigates whether in stress-prone subjects, carbohydrate-rich, pro- tein-poor food (CR/PP) prevents a deterioration of mood and performance under uncontrollable laboratory stress conditions. The assumption was that in stress- prone subjects there is a higher risk of serotonin deficiency in the brain and that carbohydrates may prevent a functional shortage of central serotonin during acute stress, due to their potentiating effect on brain tryptophan. Twenty-four subjects with a high stress-proneness (HS) and 24 subjects with a low stress- proneness (LS) participated in an uncontrollable stress situation under both a CR/PP and a protein-rich, carbohydrate-poor (PR/CP) diet condition. The plasma ratio of tryptophan to the other large neutral amino acids (LNAA) (ratio Tryptophan/LNAA) was determined as a measure indicating the dietary effect on brain tryptophan and serotonin levels. Significant increases were found in the ratio tryptophan/LNAA during the CR/PP diet compared with the PR/CP diet. Experimental stress had significant effects on pulse rate, skin conductance, cortisol and mood in all subjects. During the CR/PP diet only the HS subjects did not show the stress-induced rise in depression, decline in vigour and cortisol elevation that they showed after the PR/CP diet. With respect to cognitive performance, significant dietary effects were found on reaction time. It is suggested that CR/ PP food in HS subjects may increase personal control, probably under the influence of higher levels of brain tryptophan and serotonin.  1998 Academic Press The authors wish to thank Dr Harry Koelega for reading the manuscript and Mr Bert Molenkamp for his technical assistance. This study was supported by a research grant from Mars Confectionery, U.K. Address correspondence to: C. R. Markus, Department of Psychonomics, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands. 0195–6663/98/010049+17 $30.00/0  1998 Academic Press