Scientists from the Science Foundation Ireland-funded APC Microbiome Institute have shown that a combination of two prebiotics– soluble fibres fructo- (FOS) and galacto-oligosaccharides (GOS) – could modulate anxiety, cognition and stress-related behaviours in healthy mice.

The research also shows that these prebiotics modified specific gene expression in key brain regions. FOS/GOS treatment also reduced chronic stress-induced elevations in stress hormones and immune factors in addition to stress-induced depressive-like and anxiety-like behaviour.

UCC professors John Cryan and Ted Dinan, leaders of the research on prebiotics and stress. Photograph: Catherine Buckley/APC Microbiome Institute  

UCC professors John Cryan and Ted Dinan, leaders of the research on prebiotics and stress. Photograph: Catherine Buckley/APC Microbiome Institute

We asked Prof John Cryan of the APC Microbiome Institute at University College Cork some follow-up questions about the study.

How can people in the general population improve their gut biome?

The field is still at an early stage but what we do know is that there are a number of factors that negatively influence our microbiomes so we should avoid these. Most importantly we should only use antibiotics when necessary.

Diet is the main way to modify the microbiome so we should have a diverse diet. Cutting down on processed food, emulsifiers and sweeteners is key. Stress and sleep disturbances/jetlag all affect the microbiome. Avoiding C-Section and supporting breastfeeding are key early in life. Interestingly, having a pet also increases diversity.

How new is the field of nutritional psychiatry?

This is a relatively new field but in essence goes back millennia to Hippocrates. The first international congress on the topic took place in 2015 and Lancet Psychiatry published a key review on it signalling its becoming mainstream in medicine:

[The second international meeting takes place this summer and Prof Cryan will be giving one of the Keynote Lectures at it]

How would you define “psychobiotics”?

Originally they were defined by Prof Ted Dinan, Prof Catherine Stanon and [Prof Cryan] at the APC Microbiome in Cork as live bacteria (probiotics) which, when ingested, confer mental health benefits through interactions with commensal gut bacteria. More recently, together with colleagues in Oxford, they have expanded this definition to encompass prebiotics, which enhance the growth of beneficial gut bacteria and other means to modify the microbiome:

What foods help improve gut microbiome (other than fermented foods)?

In general prebiotic foods, those high in fibre including a variety of vegetables such as Jerusalem artichoke, garlic, leeks, asparagus. Also bananas. Foods rich in polyphenols (berries, dark chocolate, red wine, grape juice) and omega 3 fatty acids.

Are there ways of enhancing/combining these foods to make them even more effective?

Yes, indeed, but we need to test such diet mixtures in proper randomised controlled trials.

What new things are we learning about diet and stress?

We are learning that diet may be one of the best ways to target the microbiome to reduce the stress response. Our animal study with prebiotics having marked anti-stress effects supports this and now human studies are warranted.

What advances have been made about diet and illness, in more general terms?

In general we are seeing the power of diet and nutrition to both positively and negatively affect health. We are understanding the power that diet has in modulating the microbiome and thus the brain in health and disease. ( The first controlled trial of a successful diet-based adjunctive intervention in major depression was just published this past week:, which is a real step in the right direction.

And finally how long before dietary strategies will be used to target stress-related disorders such as depression and anxiety in humans?

Hopefully within three to five years the appropriate clinical studies should be completed.

We’d like to thank Prof Cryan for taking the time to answer these questions.

Team Alchemy