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Friday 8 December 2023 Dublin: 9°C

Could gut bacteria actually help reduce stress?

This scientist thinks so – and he’s not the only one.

IT MIGHT BE a little hard to believe, but there is new scientific evidence to show that your gut (and more importantly the bacteria in there) can affect your brain.

Dr John Cryan has been studying the effect of microbes in the gut and their influence on the brain and believes that in time it may be possible to target brain disorders such as depression or Alzheimer’s via the gut by administering the right sorts of bacteria to it.

We’re only beginning to understand fully how the microbiome impacts health. Brain health is one of the most difficult ones to look at – and one of the most important.

Bacteria – the good, the bad and the ugly

Bacteria generally get a bad rap. They’re responsible for illnesses and disease and are, for the most part, not welcome round these parts.

Giphy Giphy

But there is such a thing as good bacteria – and that’s what Dr Cryan is studying at the moment. He and his team are deeply involved in finding out which microbes are good for us and why and some of the results are nothing short of game-changing – in neuroscience terms, at least.

Believe it or not, the human body is actually 99% microbial – meaning made up of bacteria, and this is the first time there’s been a definitive link between gut and brain activity. So having a ‘gut reaction’ to something could actually be more than a saying.

Giphy Giphy

What Dr Cryan has discovered is that the presence of certain microbes in the gut can actually reduce stress in healthy human subjects.

For a neuroscientist to study anywhere south of the neck is quite unusual – in fact, Dr Cryan says it’s pretty much unprecedented.

This is a complete paradigm shift in the neuroscience field. This is thinking below the neck and that’s something that we’re not used to doing as neuroscientists. We need to think about whole body systems working in concert to be able to tackle disorders.


Giphy Giphy

It would be safe to say that every person in the world has experienced stress to some degree at some point in their lives.

Stress can affect you in a variety of ways from interrupting your sleep at night to creating memory problems or even debilitating anxiety.

So, finding a cure – or at the very least another way to help mitigate the effect of stress is of vital importance, to all of us. And this is how they do it:

We stress individuals and look at how they respond to a psychological stress like public speaking or a validated test like putting their hand in cold water – the amount of stress response.
We also look at them psychologically in response to the stress and we found that (after the administration of certain bacteria) they don’t have the same anxiety around the stress, that their biological stress response is blunted.

Dr Cryan’s team isn’t the only team studying microbes – although they are the only team in Ireland.

A team in UCLA has had similar quantifiable results:

Groups in UCLA a couple of years ago did a brain imagery study where they put healthy people into an MRI and were able to show that after partaking of a specific fermented milk product that contained five probiotics, their response to stress in terms of brain imaging were greatly diminished when they were put in a stressful situation and when they were given an emotional task to do.

So, is a cure for stress on the cards? Dr Cryan thinks so. In fact, he thinks that in 5-7 years ‘we may have a product on the market that has been scientifically tested rigorously to show that it has positive effects on mental health’.

Science Week takes place from 8-15th November 2015. This is Science Week’s 20th birthday, and the theme for this year is Science Week 2.0 – Design Your Future. Over the course of the week, there will be 800 events held nationwide, with an participating audience of 250,000. For events in your area, check out

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