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Dieting reduces plasma tryptophan and alters brain 5-HT function in women

  • I. M. Anderson (a1), M. Parry-Billings (a1), E. A. Newsholme (a1), C. G. Fairburn (a1) and P. J. Cowen (a1)...

A three week low calorie diet significantly reduced both total plasma tryptophan and the ratio of tryptophan to competing amino acids in a group of 15 healthy volunteers. Despite a similar percentage weight loss the reduction in plasma tryptophan was greater in women than men. In addition, only in women was dieting associated with increased prolactin secretion following intravenous tryptophan, a measure of brain 5-hydroxytryptamine (5-HT) function. These results suggest that dieting reduces the availability of circulating tryptophan for brain 5-HT synthesis. Women appear more vulnerable than men both to this effect and to its consequences for brain 5-HT function. Altered brain 5-HT function may play a part in some of the psychological consequences of dieting, including the development of clinical eating disorders.

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1Address for correspondence: Dr P. J. Cowen, Research Unit. Littlemore Hospital, Oxford OX4 4XN.
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Psychological Medicine
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