(Poly)phenols and mental health:role of the gut-brain axis
Mental health disturbances and stress-related symptoms are increasingly prevalent across the life course, with young adulthood and midlife in women, particularly during the menopause transition, representing periods of increased vulnerability. In young adults, particularly university students, the transition to adulthood involves academic, social, and financial pressures, coinciding with the period when many common mental disorders first emerge, typically before age 25. In women, menopause is linked to mood disturbances, anxiety and depressive symptoms, driven by hormonal fluctuations, sleep disruption, vasomotor symptoms and psychosocial stressors. Dietary (poly)phenols, bioactive compounds abundant in plant-based foods, are emerging modulators of mental well-being, with growing evidence for gut–brain axis related mechanisms involving gut microbiota, microbial metabolites and neuroendocrine pathways. In a scoping review we have recently conducted, human studies consistently reported benefits of dietary (poly)phenols for depressive symptoms and mood, while effects on stress and anxiety were less consistent. The review also highlighted key limitations in the current literature, including heterogeneity in study designs, populations, interventions and outcome measures, variable dosages and durations of supplementation, and inconsistent assessment of both (poly)phenol intake and mental health outcomes, which together limit comparability and interpretation of findings.This lecture will present evidence from recently conducted observational and intervention studies examining relationships between (poly)phenol intake, circulating metabolites, stress physiology, cognition, gut microbiota and mental health in university students and postmenopausal women.
In a cross-sectional study of over 300 university students, higher intakes of anthocyanins, flavanones, flavonols and tyrosols were associated with lower stress, anxiety, depression and mood disturbances, while higher consumption of flavan-3-ols was associated with reduced cortisol levels, with multiple urinary metabolites supporting biological plausibility. In a double-blind randomised controlled trial, 12 weeks of (poly)phenol-rich cranberry supplementation did not alter self-reported mood or distress but reduced diurnal cortisol and improved short-term and phonological memory, alongside modulation of gut–brain axis metabolites, suggesting that physiological and cognitive benefits may occur independently of perceived mental health changes.
Preliminary data from a double-blind crossover trial in postmenopausal women examined whether (poly)phenols alone or combined with probiotics could alleviate menopause-related symptoms via gut microbiota pathways. Both interventions supported well-being but through distinct mechanisms: the combined intervention enhanced cognition, including learning, memory and concentration, with increased (poly)phenol bioavailability and propionate-producing taxa, whereas the (poly)phenol-only intervention was linked to greater vitality, sexual activity and motivation, with higher abundance of butyrate-producing bacteria.
These findings highlight dietary (poly)phenols as modulators of stress regulation, cognition and mental health across life stages, with emerging evidence supporting a role for gut–brain axis pathways.
