Anxiolytic effect of prebiotics in young women. British study


Regular consumption of prebiotics may have anxiolytic effect in young women, promoting their mental health in adulthood. The evidence emerges from a study conducted by researchers at the University of Surrey (UK) School of Psychology, published in Scientific Reports. (1)

Anxiolytic effect of prebiotics

The gut microbial community (microbiome) is not immutable. Throughout life, the microbiota is indeed subject to alterations attributable to lifestyle, diet in the first place, as well as stress. With various consequences, as we have seen.

Gut microbial composition (…) regulates gene expression and metabolite release in the brain,’ the researchers explain, reminding that imbalance of the gut microbiome affects mental health and is also associated with pathological emotional conditions, such as autism, depression, and anxiety. (2)

The origin of mental health

Replicating the pattern of a study in adults that showed the anxiolytic and stress-relieving effect of prebiotics (Schmidt et al., 2015), (3) the British researchers aimed to confirm the evidence in young women, with the prospect of ensuring their mental well-being in adulthood.

In fact, as the researchers explain, ‘The transition period from adolescence to adulthood represents an important developmental time for both the emergence of social anxiety and the development of emotion control skills, which enable individuals to control their fear and anxiety responses.’

The study

In the study, 64 women aged 18 to 25 years received 7.5 g of a GOS (galacto-oligosaccharide prebiotic) supplement or a placebo (a mixture of maltodextrin, dried glucose syrup) once daily for 28 days.

GOS are referred to as prebiotics. They are nondigestible carbohydrates that reach the gut relatively intact, where they are then available to the microbiota. Simplifying, they feed the ‘good’ bacteria in the gut. Prebiotics, such as fructans and oligosaccharides, are moreover naturally present in grains, fruits and vegetables.

The result

By means of psychological assessments of the participants’ anxiety and mood levels, the researchers found confirmation of the anxiolytic effect of prebiotics (GOS) particularly in highly anxious women, as well as a modulation of emotional tendency( emotionalbias ) toward positive feelings.

Benefits also emerged in the composition of the participants’ gut microbiota, with an increase in Bifidobacterium, bacteria associated with emotional well-being.

The frontier of psychobiotics

In the study under review, the British researchers chose to experiment with prebiotic administration only, so as not to interfere with the volunteers’ microbiota by adding probiotics. But research on the relationship between the microbiome and mental well-being also rests extensively on psychobiotics, preparations of mixes of probiotics and prebiotics.

Rat experiments found‘robust and reproducible‘ effects on stress, anxiety and depression after administration of psychobiotics. However, the translatability of these psychological effects on humans is still a subject of research.

Marta Strinati

Cover image by Niamh Young, Serendipity, watercolor on paper


(1) Johnstone, N., Milesi, C., Burn, O. et al. Anxiolytic effects of a galacto-oligosaccharides prebiotic in healthy females (18-25 years) with corresponding changes in gut bacterial composition. Sci Rep 11, 8302 (2021).

(2) V.

Parracho, H. M., Bingham, M. O., Gibson, G. R. & McCartney, A. L. Differences between the gut microflora of children with autistic spectrum disorders and that of healthy children. J. Med. Microbiol. 54, 987-991. (2005).

Mayer, EA, Knight, R., Mazmanian, SK, Cryan, JF & Tillisch, K. Gut microbes and the brain: Paradigm shift in neuroscience . J. Neurosci. 34 , 15490-15496. (2014).

Mayer, E. A. Gut feelings: The emerging biology of gut-brain communication. Nat. Rev. Neurosci. 12, 453-466. (2011).

Morkl, S., Butler, M. I., Holl, A., Cryan, J. F. & Dinan, T. G. Probiotics and the microbiota-gut-brain axis: Focus on psychiatry. Curr. Nutr. Rep. 9, 171-182. (2020).

(3) Schmidt, K. et al. Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers. Psychopharmacology 232, 1793-1801. (2015).

Marta Strinati

Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".