We all want to stay mentally healthy as we age – but with the number of people living with dementia forecast to hit one million by 2030, that’s far from a guarantee.

It’s why more and more of us are on the hunt for ways to take care of our brains and optimise our cognitive function, whether in the form of brain-training puzzles, physical exercise or a healthy diet. But according to the latest research, there could be another way to reduce your risk of developing dementia: taking care of your gut microbiome.

The link between the gut and the brain (the gut-brain axis) is often discussed in terms of its mental health implications, but now experts believe that relationship could play a role in building and maintaining cognitive function. We asked two gut health experts to explain all.  

Before we get into the link between gut health and cognitive disease, let’s just remind ourselves of how that connection between the gut and the brain works.

“The gut and the brain are constantly talking to each other,” explains Dr Sammie Gill, Symprove’s registered gastroenterology dietician. “They communicate in numerous ways, including through the nervous system, immune system, hormonal system and gut microbiome. In fact, the gut is often called the ‘second brain’ because it can control gut behaviour independently of the brain.”

In simple terms, this relationship means that what goes on in the gut will have an impact on the brain, and vice versa. It’s for this reason that making gut-friendly lifestyle changes such as taking probiotics has been shown to alleviate symptoms of mental health conditions such as depression, and high levels of stress can lead to digestive discomfort: it’s a domino effect.  

This link also means our gut health can impact how well our brains work – aka, our cognitive function. “Our gut microbiota has been linked to improvements in various aspects of our cognitive function, including memory, emotional reactivity and attention span,” explains Dr Nabeetha Nagalingam, a microbiome expert and lead scientist at Omed Health and Owlstone Medical.

“While there’s still more research to be done in the area to identify exactly how our microbiota impact our cognitive function, this suggests an exciting potential for enhancing our cognitive ability by making specific changes to our microbiome.” 

While research into this relationship is still ongoing, emerging evidence suggests that the gut microbiome could have a part to play in many brain-related disorders.

For example, a study of mice published in 2020 found that changes in the gut microbiome, including dysfunction of the intestinal barrier, occurred before signs of Alzheimer’s (one of the most common types of dementia) could be observed in the brain.

“These problems mean that the gut could be involved in how Alzheimer’s develops and how fast and far it progresses,” Dr Nagalingam explains. “Changes in the composition of our gut bacteria could also possibly contribute to the development of these conditions.

“For example, there is evidence that certain gut bacteria might influence the build-up of harmful proteins in the brain or make our brains more prone to inflammation, which are both linked to Alzheimer’s and other brain diseases.” 

Indeed, studies have shown that the gut microbiota of people with dementia could have a direct link on brain health; one such piece of research published at the end of last year found that, when stool samples from Alzheimer’s patients were transplanted into microbiota-depleted rats, those rats showed memory impairments symptomatic of the disease.

Changes in the way our bodies process bile acids – compounds which help our digestive system to break down fats and play a key role in our gut microbiome composition – have also been linked to Alzheimer’s disease, suggesting another way in which the gut could play a role.

Of course, any studies done on rats need to be replicated in humans in order for the findings to be truly significant. However, Dr Nagalingam says preliminary research is interesting: “While there is still a lot to learn about how exactly our gut bacteria affect our brains, it is clear that keeping our gut healthy could be key to keeping our minds sharp as we age.” 

Research into the link between cognitive health and the gut microbiome has also led to the development of potential treatments and interventions.

“There has been a surge of interest in how specific bacteria may affect the brain, also known as psychobiotics,” Dr Gill points out. “In terms of where the science is at, some research groups have identified a number of promising candidates.”

These ‘candidates’ include species from the bifidobacteria family, a group of bacteria which digests dietary fibre and helps to prevent infection, among other roles. Research into bifidobacteria has shown it could play a role in the regulation of anxiety, mood, cognition and pain.

The types of bacterial deficiencies observed in those with memory issues could also lead to targeted interventions. “When it comes to conditions like Alzheimer’s and mild cognitive impairment (MCI), some studies have found that changes in the types of bacteria living in our guts could be linked to these diseases,” Dr Nagalingam explains.

“For example, people with MCI seem to have lower levels of certain bacteria like ruminococcus and butyricimonas. These changes in gut bacteria seem to be connected to how well our brains work, especially when it comes to things like attention and problem-solving.”

Both of these types of bacteria are naturally found in a healthy human gut, but they can be reduced in number due to harmful habits such as regularly drinking alcohol or not eating enough fibre.

While we’re not at a point where any of these interventions are widely used, it’s clear that taking care of your gut health in general – and in turn encouraging the growth of healthy bacteria – could be a simple way to reduce your risk of cognitive issues in the future.

“It is important to remember that gut health is extremely personal – your gut microbiome is as unique as a fingerprint and varies hugely from that of others,” Dr Nagalingam adds. “Contrary to what a product may be advertising, there is no such thing as a one-size-fits-all solution for gut health.”

Instead, stick to the simple things if you want to give your gut health a boost. Easy steps you can take include upping your fibre intake, exercising regularly, staying hydrated and eating fermented foods on a regular basis, as well as reaching for a probiotic in some cases.  

Images: Getty