Volume 91, Issue 3, March (2004), pp. 351-355 © The Author 2004
doi:10.1079/BJN20031055

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Acute tryptophan depletion slows gastric emptying in females

Michiel A. van Nieuwenhoven¹, Sabine D. M. Valks¹, Sjacko Sobczak², Willem J. Riedel², Robert-Jan M. Brummer^1
1Department of Gastroenterology, University Hospital Maastricht, Maastricht, The Netherlands
²Department of Psychiatry and Neuropsychology, University Hospital Maastricht, Maastricht, The Netherlands

 (Received 26 February 2003–Revised 25 September 2003–Accepted 3 November 2003)

Serotonin (5-HT) is an important neurotransmitter involved in the brain–gut axis. It is possible to lower the 5-HT level in the body by means of a nutritional intervention using an amino acid mixture; the acute tryptophan depletion (ATD) method. We studied the effect of ATD on gastric emptying in healthy females, who received both ATD and placebo in a random order. Gastric emptying was measured using the [¹³C]octanoic acid breath test. The present data demonstrate significant differences in both gastric emptying and lag phase (Tlag) between the ATD and placebo experiment. Eight out of ten subjects showed a delayed gastric emptying in the ATD experiment. Both the gastric half-emptying time (T1/2) and the Tlag were significantly higher in the ATD experiment. T1/2 in the ATD experiment was 137·2 (range 76·2–634·8) min; T1/2 for the placebo experiment was 98·5 (range 63·7–168·8) min (P=0·028). Tlag in the ATD experiment was 83·7 (range 45·1–356·2) min; Tlag for the placebo experiment was 56·9 (range 23·2–101·2) min (P=0·007). We conclude that lowering the 5-HT level in the body using the ATD method leads to a significantly delayed gastric emptying of a solid meal. Nutritional manipulation of the serotonergic system in healthy volunteers may lead to alterations in gastrointestinal motility.

Keywords:
Tryptophan depletion, Gastric emptying, Serotonin, Amino acids

Abbreviations:
ATD, acute tryptophan depletion, 5-HT, serotonin, LNAA, large neutral amino acids, T1/2, gastric half-emptying time, Tlag, lag phase