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??-Lactalbumin is a tryptophan-rich protein fraction. A diet enriched with ??-lactalbumin increases the ratio of tryptophan to the other large neutral amino acids, which may in turn increase brain serotonin content. In stress-vulnerable individuals, ??-lactalbumin improved mood and attenuated the cortisol response after experimental stress. The aim of the present study was to investigate the effects of an ??-lactalbumin-enriched diet on mood and stress response in recovered depressed subjects and healthy controls. Forty-three subjects (twenty-three recovered depressed and twenty healthy subjects) received ??-lactalbumin and casein (placebo) on separate days, in a double-blind randomised crossover design. On both occasions, subjects underwent a stress test (an unsolvable mental arithmetic task with loud noise). The stress test affected mood in both conditions. Although the ??-lactalbumin diet led to the expected rises in tryptophan and tryptophan:large neutral amino acids ratio, only minimal effects were found on mood and cortisol response to experimental stress. The results were the same for recovered depressed patients and controls. A 1 d diet enriched with ??-lactalbumin is not sufficient to prevent a stress-induced mood deterioration or a cortisol response in unmedicated, recovered depressed subjects. Future studies may investigate the effects of longer-term diets or may investigate different samples (e.g. medicated patients). [ABSTRACT FROM PUBLISHER]

Background: Acute tryptophan depletion transiently induces symptoms in those with remitted depression. The behavioural specificity is uncertain, however. Recently, symptom provocation studies have become controversial, particularly in the USA.Aims: To assess the specificity of acute tryptophan depletion. To investigate systematically the subjective experiences of those taking part in a symptom provocation study.Method: Twenty individuals with remitted depression underwent acute tryptophan depletion in a double-blind, crossover trial. Psychiatric symptoms and self-schemata relevant to depression were assessed. The quality of the informed consent procedure and subjective experiences were also evaluated.Results: Acute tryptophan depletion induced a specific depressive response. The effects were more pronounced in females than in males. Participants were quite satisfied with the informed consent procedure. They had understood that this was a fundamental research project and personal benefits were not expected. However, some participants still found it a positive experience.Conclusions: Acute tryptophan depletion is a suitable model of vulnerability to depression, from both a scientific and an ethical perspective. [ABSTRACT FROM AUTHOR]