HERE'S a good quiz question, courtesy of UCC Professor John Cryan. “What weighs about 3lbs and influences everything we do?”
No, it’s not the brain but the bacteria within your gut.
As Prof Cryan puts it, “those pesky little critters might just be the master puppeteers of our brain and our bodies.”
With Prof Ted Dinan and the team at the APC Microbiome Institute in Cork, he has already shown how taking a probiotic daily can reduce stress and improve memory.
In a small study last year, researchers at the Institute gave 22 healthy male volunteers the bacterial strain, Bifidobacterium longum 1714, daily, for four weeks.
The volunteers taking it said they felt less stressed, something that was confirmed by tests on their levels of the stress hormone, cortisol.
They also felt other benefits. Their brain function improved significantly and, in particular, memory.
Now, the Institute is exploring other ways of harvesting gut bacteria to improve mental health. The early results are very encouraging.
In a recent study on mice, researchers focused on the health benefits of prebiotics as opposed to probiotics.
Unlike probiotics, which have to be alive and survive the acid in the stomach, prebiotics come from the diet.
In the study, mice were given a high concentration of two prebiotics, soluble fibres fructo (FOS) and galacto-oligosaccharides (GOS), which are similar to those found in green vegetables, onions, leeks, Jerusalem artichokes and breast milk.
“We were amazed by the robustness of the changes we saw and how effective [the prebiotic] was — it could change brain chemistry quite dramatically.
"The study showed that gut microbiota could counter a lot of the effects of stress, including how it affects the immune system, behaviour and what is going on in the brain. By promoting the growth of beneficial bacteria, we can modulate brain function,” Prof Cryan said.
If those findings could be translated to humans, he added, it would open the way for a whole new ‘psychobiotic’ way of managing stress-related disorders, such as depression and anxiety disorders.
And that possibility is a lot closer than you might expect.
The first study on diet and depression, carried out recently in Australia, found that a Mediterranean-style diet helped those suffering from depression.
Researchers at Deakin University put dozens of patients — who were treating their depression with antidepressants — on a diet of wholegrains, legumes, fresh fruit and vegetables, olive oil and nuts, which are all rich in prebiotics.
One third of those taking part reported a significant improvement in their mood after 12 weeks on the diet — further evidence that our gut microbiota has a role to play in mental health.
The researchers, however, warned that diet alone should not replace traditional medical treatments for depression.
Back in Cork, Prof Cryan and his 45-strong team in the gut-brain division of the APC Microbiome Institute are in the early stages of translating these, and other encouraging findings into ways of using prebiotics to improve mental health.
“Prebiotics are already in the diet so you don’t have to manufacture them,” Prof Cryan explains.
That’s a plus, but more evidence is needed along with time-consuming clinical trials.
All the same, the introduction of stress-busting ‘psychobiotics’ could happen within the next five years, he predicts.
In the meantime, there is still a lot we can do to nurture and protect our microbiome.
It’s been shown that antibiotics destroy beneficial bacteria, but it’s also harmful to live in an over-clean, sterile environment as those conditions kill good bacteria as well as bad.
You can also eat to help your gut.
A diet rich in fermented foods, such as kefir, green vegetables and fibre has been shown to be beneficial, Prof Cryan says.
Foods to eliminate include all processed foods, those high in emulsifiers, such as ice cream, and artificial sweeteners.
The jury is still out on alcohol.
It has been shown to have a negative effect on mice, but red wine is high in polyphenols, which are good for the microbiome.
All the findings need further study but, as Prof Cryan says, it looks as if “the secret to our own happiness may not lie in the self-help bookshop of the local bookstore but maybe within — in your microbiome.”