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Tryptophan and depression: can diet alone be the answer?

  • Nerissa L. Soh (a1) and Garry Walter (a1) (a2) (a3)

Objective: To compare the scientific content of recent general media articles on tryptophan, diet and depression, with recent empirical research into dietary manipulation of tryptophan published in the scientific literature.

Method: A review of the recent empirical research into the role of tryptophan in depression, focusing on dietary methods to influence tryptophan levels. In parallel, a review of recent articles in the general English language media regarding tryptophan and mood.

Results: Empirical evidence for improving mood through dietary manipulation of tryptophan is lacking, and it is difficult to change plasma tryptophan levels through diet alone. Tryptophan supplementation and depletion studies suggest that altering tryptophan levels may only benefit certain groups of patients who have a personal or family history of depression. Scientific studies also focus on elucidating mechanisms in depression, rather than treating depression by changing tryptophan levels. However, general media articles often recommend diets and foods to increase blood tryptophan levels and raise brain serotonin levels. Such recommendations are not supported by scientific studies.

Conclusion: It is very difficult to alter blood tryptophan levels through dietary methods alone, outside of a laboratory or research setting. Only a small number of lay articles provide sound advice, with general media reports on tryptophan often being hyperbolic and misleading. A clinician should be aware of the type of (mis)information a patient may have accessed and have the scientific knowledge to explain the impracticalities of influencing tryptophan levels through diet alone.

Corresponding author
Dr Nerissa L. Soh, Child and Adolescent Mental Health Services, Northern Sydney Central Coast Area Health, Coral Tree Family Service, PO Box 142, North Ryde NSW 1670, Australia. Tel: +61 2 8877 5371; Fax: +61 2 9887 2941; E-mail:
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