Microbiome Insight of the Month - May
'The role of polyphenols and the gut-brain axis in Perimenopausal depression'
by Ashley Roy
The gut-brain axis - the bidirectional communication network linking our gastrointestinal tract and central nervous system - is becoming more recognised as a key player in mental health. Now, emerging research is illuminating how polyphenols can influence this axis in ways that may reduce specific perimenopausal symptoms linking to anxiety and depression.
One subclass of polyphenols, lignans, has attracted growing scientific interest for their ability to interact with the gut microbiome and produce metabolites with oestrogen-like activity. This is particularly relevant during perimenopause when declining oestrogen levels can drive a heightened vulnerability to depression and anxiety, alongside well-documented shifts in gut microbiome composition.
This 2026 randomised controlled trial investigated whether dietary lignan supplementation could alleviate perimenopausal depressive symptoms. The study assessed the effect of 4 weeks’ dietary lignan supplementation on 64 female participants. It highlights the biological pathways involved in polyphenol intake and mood improvement.
Key Findings:
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Polyphenols can benefit perimenopausal women suffering with depression. One month of dietary lignan supplementation significantly reduced both depressive and anxiety symptoms in perimenopausal women and was associated with elevated serum oestradiol levels.
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The gut microbiome acts as a critical intermediary. The antidepressant effect is not direct - it depends on the gut microbiome first converting lignans into their bioactive metabolites, enterolactone and enterodiol. Supplementation was associated with increased activity of the enzyme β-glucuronidase and enrichment of the gut bacterium Bacteroides ovatus, both instrumental in this conversion. This highlights how microbial composition shapes the therapeutic potential of dietary compounds.
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Establishing a clear gut-brain neuroplasticity pathway, with this study finding that the microbially-produced lignan metabolites activate oestrogen receptor beta (ERβ) in the hippocampus - a brain region central to mood regulation and memory. This in turn upregulates expression of the synaptic proteins GluN2A and PSD95, enhancing neuronal plasticity.
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Microbial functional capacity may be the limiting factor, as the pathway relies on microbial conversion of lignans. The diversity and functional capacity of an individual's gut microbiome determine how much benefit they can extract from dietary polyphenol intake. Those with lower microbial richness may convert fewer lignans into their active forms.
This study advances mechanistic understanding of the gut-brain axis by demonstrating that microbial conversion of dietary lignans is a prerequisite for their antidepressant effect - positioning the gut microbiome as a key determinant of therapeutic response. It highlights dietary polyphenols as a biologically plausible adjunctive strategy, particularly where declining oestrogen and microbiome shifts converge to increase mood vulnerability.
It is worth noting the limitations of this study - a one-month intervention period and partial reliance on animal models. However, while we await longer-duration trials alongside baseline microbiome profiling, this study provides some key insights into how polyphenols can help perimenopausal women suffering with mood disorders.
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