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.

To conduct a critical review of recent empirical research regarding mood, behaviour and nutrition factors including essential fatty acids, macronutrients, micronutrients and food additives.

A literature search of databases Medline, PsycInfo, CINAHL and Embase up to October 2008. The search emphasised empirical research published in the last 10 years and also included older literature. Studies in both adults and children were addressed.

Research into omega-3 fatty acids has been substantial but evidence for their potential in treating mood and behaviour is modest. In comparison, there has been much less research into carbohydrate and protein intakes and little evidence for their ability to influence mood and behaviour. Recent trials with food additives suggest their removal from the diet may benefit susceptible children with hyperactivity disorders. Micronutrient supplementation appears to improve mood only in those who were initially deficient in micronutrients.

More stringent research designs such as longitudinal studies and the use of biologically inert placebos within randomised controlled trials are needed before supplemental use of omega-3 fatty acids to treat disorders of mood and behaviour can be recommended. Caution is advised regarding the indiscriminate use of diets free of artificial food additives in managing hyperactivity disorders, as they may place an undue burden on individuals and their families. Should omega-3 fatty acid supplementation or the elimination of certain food additives be established as effective, they may provide cost-effective, accessible and well-tolerated adjuncts to standard psychiatric treatments for mood and behavioural disturbances.