Tryptophan and Kynurenine Pathway Metabolites and Psychoneurological Symptoms Among Breast Cancer Survivors.
Hongjin Li, Mark B Lockwood, Judith M Schlaeger and 3 others
PMID 36229337WHAT IT FOUND
Breast cancer survivors reporting more pain, fatigue, sleep disturbance, depression and anxiety had lower serum tryptophan and higher kynurenine-to-tryptophan ratio.
This is an association, not a treatment result.
Key findings
01About 19% of participants formed a high symptom subgroup with pain, fatigue, sleep disturbance, depression and anxiety.
02Lower tryptophan levels were associated with the high symptom subgroup.
03Higher kynurenine-to-tryptophan ratios remained associated with the high symptom subgroup after adjusting for BMI and antidepressant status.
STILL TO COME
How it was doneWhat they foundWhat it means for RNs
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What it does not show
Only 79 survivors were studied, and the authors call this a pilot, so the symptom subgroups and metabolite associations may not be stable. The study was cross-sectional, so it cannot show whether tryptophan changes caused symptoms or were linked to symptoms at the same time. Metabolites were only semi-quantified, not measured as absolute concentrations. Only selected tryptophan pathway metabolites were tested, so other metabolic pathways were not assessed. Participants came from one clinic and were mostly Black with stage I breast cancer, so the results may not apply to all breast cancer survivors.
Declared interests
The authors declared no potential conflicts of interest. The article is identified as receiving NIH extramural research support.
The easy way to misread this
Do not read this as proof that low tryptophan causes symptoms or that a tryptophan-rich diet will improve them. The study was cross-sectional, used semi-quantitative metabolite measures, and did not test diet or treatment.