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Fatigue: a biochemical imbalance?

Fatigue is a common symptom experienced by many sufferers of chronic diseases, including patients suffering from cancer. While treatment of fatigue is made difficult due to its multi-factorial aetiology, new research has drawn correlations between disturbed tryptophan metabolism and fatigue.

Many patients who suffer from cancer experience fatigue. Unfortunately, fatigue can be a difficult symptom to treat due to the wide variety of possible causes underlying it. Seeking to shed some light on this difficult-to-treat symptom, a group of Austrian researchers looked for a common link to some of the hypothesised causes of fatigue – anaemia, depression and inflammation. Based on studies that found a link between behavioural symptoms and cytokine (inflammatory markers) production, and studies linking disturbed tryptophan metabolism  with cytokine production, the authors hypothesised a link between inflammation, disturbed tryptophan metabolism and behavioural symptoms contributing to fatigue.  As such, Kurz and colleagues conducted a study to assess the relationships between quality of life, fatigue, inflammation, anaemia and tryptophan metabolism.

This study is fantastic because it demonstrates just how multi-factorial cancer-related fatigue is, and contributes to the growing literature exploring the importance of understanding individual differences in the management of diseases.

While this study examined fatigue in cancer patients, the pathway of decreased tryptophan can also be applied to stress-induced fatigue.  Chronically elevated cortisol has also been shown to correlate with impaired tryptophan metabolism resulting in fatigue and depression.


Kurz K, Fiegl M, Holzner B, Giesinger J, Pircher M, Weiss G, Denz HA, Fuchs D. Fatigue in patients with lung cancer is related with accelerated tryptophan breakdown. PLoS One.
2012;7(5):e36956.; and

Taeben Davis BHSc (Nut Med)