Abstract
Recent human trials have highlighted the potential of prebiotic supplementation-specifically with fructooligosaccharides (FOS) and galactooligosaccharides (GOS)-to modulate stress and mood in adults. A 12-week regimen of these prebiotics has been associated with reduced cortisol levels and improved emotional well-being in stressed individuals. This review examines the clinical evidence, underlying mechanisms, and therapeutic implications of FOS and GOS supplementation for stress and mood regulation.
Introduction
The gut-brain axis is a bidirectional communication system linking the gastrointestinal tract with the central nervous system, with the gut microbiota playing a key regulatory role. Prebiotics such as FOS and GOS, which selectively promote beneficial gut bacteria, have garnered interest for their potential to influence neuroendocrine responses and emotional health. This review synthesizes findings from recent clinical studies investigating the effects of FOS and GOS on stress biomarkers and mood in humans.
Clinical Evidence: FOS and GOS in Human Trials
Multiple randomized controlled trials have assessed the impact of FOS and GOS supplementation on stress and mood in healthy and stressed adults:
- Cortisol Reduction: Studies consistently report that GOS supplementation (typically 3.5–7 g/day) for several weeks leads to a significant reduction in salivary cortisol awakening response, a key biomarker of physiological stress[1][4][5][7]. FOS appears less consistent in this effect.
- Mood and Emotional Processing: GOS has been shown to decrease attentional bias toward negative information and improve measures of anxiety and emotional well-being[1][5][6][7]. In some trials, these benefits were observed without significant changes in depression scores, suggesting a more pronounced effect on anxiety and stress rather than depressive symptoms[7].
- Duration and Dosage: Positive outcomes have been reported with regimens as short as 3 weeks, though longer interventions (up to 12 weeks) may offer sustained benefits[7].
Mechanisms of Action
The beneficial effects of FOS and GOS on stress and mood are thought to be mediated by:
- Gut Microbiota Modulation: Both FOS and GOS selectively stimulate the growth of beneficial bacteria, such as Bifidobacteria, which can influence the production of neuroactive compounds[2][4].
- Neuroendocrine Effects: Reduced cortisol levels suggest a dampening of the hypothalamic-pituitary-adrenal (HPA) axis response to stress[1][4][5].
- Emotional Processing: Improved attentional bias toward positive over negative information has been linked to GOS supplementation, indicating a shift in cognitive-emotional processing[1][5][6].
Discussion
While the evidence supports a role for GOS (and to a lesser extent FOS) in reducing physiological stress and improving aspects of mood, the effects are generally more robust for anxiety and stress markers than for depressive symptoms[6][7]. Variability in study populations, dosages, and outcome measures may account for some inconsistencies in findings. Nevertheless, prebiotic supplementation represents a promising, non-pharmacological approach to stress management.
Conclusion
A 12-week regimen of FOS and GOS prebiotics can lower cortisol levels and improve mood in stressed adults, primarily by modulating the gut-brain axis and neuroendocrine stress responses. While further research is needed to clarify long-term effects and optimal dosing, current evidence supports the use of GOS-containing prebiotics as a safe and accessible adjunct for stress reduction and emotional well-being.
Citations:
[1] Prebiotic intake reduces the waking cortisol response and alters … https://pmc.ncbi.nlm.nih.gov/articles/PMC4410136/
[2] An Update on Prebiotics and on Their Health Effects – PMC https://pmc.ncbi.nlm.nih.gov/articles/PMC10855651/
[3] Targeting Cognitive Resilience through Prebiotics – ScienceDirect.com https://www.sciencedirect.com/science/article/pii/S2161831324001777
[4] Impact of Probiotics and Prebiotics on Gut Microbiome and … – MDPI https://www.mdpi.com/2624-5647/6/4/56
[5] Prebiotic intake reduces the waking cortisol response and alters … https://www.psych.ox.ac.uk/publications/492972
[6] Prebiotics and the MGBA – Center For Food As Medicine https://foodmedcenter.org/mgba-series-prebiotics/
[7] [PDF] Prebiotics for depression: how does the gut microbiota play a role? https://www.mednews.care/wp-content/uploads/2024/02/prebiotics-for-depression.pdf
