Could our gut bacteria be affecting our mental health?
And if so, can we influence it to improve our mental wellbeing?
These questions have captured the attention of researchers around the world, and interest in the topic has sparked a great amount of media interest. But how strong is the current body of evidence? And should we be changing our diets to promote better gut (and mental) health? Let’s take a look.
Gut microbiota: the trillions of friends in your gut
We largely live in harmony with the vast amount of bacteria residing in our gut. These living organisms help us with a range of very important activities including:
- digesting foods and extracting their nutrients
- enhancing immunity and defending against illness and disease
- creating and releasing vitamins and other signalling molecules.
In exchange, we provide our gut flora with a steady source of nutrition and a safe place to live.
There are thousands of different types of bacteria, both ‘good’ and ‘bad’, that can live in our gut. The size and composition of each individual’s gut flora depends on many things, such as:
- early life influences (e.g. how you were delivered at birth)
- medical conditions
- antibiotic use
- and of course, diet!
The gut-brain axis
This futuristic sounding phrase is used to describe how our brain talks with our gut, and vis versa. We’re all keenly aware of the impact our brain has on our gut, like when you’re nervous you might feel queasy or experience ‘butterflies’. Similarly, our gut communicates with our brain, ideally to promote good health.
The gut can communicate through a range of different and complex pathways involving our nervous, immune, and hormonal systems. For example, some strains of gut bacteria release or activate chemical messengers (neurotransmitters) that send messages via these pathways to our brain and other body cells. Depending on the composition of our gut flora, the messages coming from our gut may be health promoting or could contribute to poorer health.
Probiotics – living, health-promoting bacteria
Probiotics are defined as living bacteria that, if ingested in adequate amounts, can have health-promoting benefits. Probiotics are more than just the refrigerated pills at your chemist. In fact, they occur naturally in a wide range of foods like:
- fermented milk drinks like kefir and traditional buttermilk
- fermented soybean products like tempeh
- fermented vegetable dishes like kimchi and sauerkraut
- miso soup
- some cheeses
Diet is a key factor in determining the composition of our gut flora. The diversity of our diet, the inclusion of prebiotics (food that our good gut bacteria particularly love), and probiotics are all thought to be influential on the complexity and stability of our gut microbiome.
The two most common types of probiotics are Lactobacillus and Bifidobacterium, which you’ve probably heard of thanks to product marketing. Foods can be fortified with probiotics, but it can be difficult to say if enough probiotics are present to have a positive effect on health. As probiotics are live bacteria, they are vulnerable to food production stages like cooking and storage, and also the rigours of our body’s digestive processes.
Anxiety – Australia’s most common mental health condition
Anxiety is one of the most common mental health disorders worldwide and the most common in Australia. Symptoms of anxiety include heightened feelings of fear, tension, nervousness and panic. It can be mild or severe, and tends to be experienced over a long period of time (chronic) rather than in short stints (episodic). Many individuals live with anxiety, although their experience is at a level that doesn’t meet diagnostic criteria for a mental health disorder.
Mental illnesses like anxiety can negatively affect many aspects of a person’s life, including employment and relationships. Mental illnesses are often comorbid (that is, commonly experienced alongside) many physical health conditions including heart disease and gastrointestinal disorders.
Probiotics have been studied as a supportive therapy for various medical conditions affecting the gut, including Irritable Bowel Syndrome (IBS) and chronic fatigue syndrome. An increasing amount of research is also exploring the link between gut microbiota and symptoms of mental health conditions including depression and anxiety.
Probiotics and anxiety – how might it work?
Research into the use of probiotics to manage symptoms of anxiety is fairly new, and most of the strong evidence comes from animal trials. Researchers are simultaneously exploring how probiotics work (what pathways are they triggering? how are they triggering them? what doses are needed?) and whether they can illicit a positive effect on symptoms of anxiety. Some fascinating answers are being revealed. For example, it has been found that some strains of gut bacteria can produce or activate biologically active agents like GABA; dysfunctional GABA signalling has been implicated in anxiety and depression. Microbiota may also influence another important pathway – the hypothalamus-pituitary-adrenal axis (HPA axis) – which is one of the main pathways that manages our body’s response to stressful situations. Gut microbiota may be able to inhibit a key communication stage, thereby suppressing our stress response.
Hold your horses
The current body of evidence into the use of probiotics for managing anxiety symptoms presents some positive but inconsistent results. The studies have mostly involved small groups of healthy volunteers and they often simulate or induce short stressful situations. This is obviously very different to a lived experience of anxiety, and so we can’t draw conclusions about their effectiveness for this population. Very few studies have looked at the effect of probiotics on people with subclinical or clinical anxiety.
The animal studies and human trials to date are pointing towards some probiotic strains as a potential treatment for anxiety, but the research is very much in its infancy. More research is needed to determine just how probiotics work, and whether they’ll work with different types of people experiencing different health conditions.
So, will probiotics help my stress and anxiety?
We can’t say that yet. More research is needed. If the research reveals a positive result, probiotics could become a low-risk, low-cost supportive treatment in the management of anxiety. Watch this space.
Should I eat more probiotic foods?
Including probiotic-rich foods in your diet is a great way to support your overall health and wellbeing. Even if we can’t confidently say if or how they might help with stress and anxiety, that’s ok. Consuming probiotics in ‘naturalistic doses’ (i.e. regular, sensible amounts) can improve our health in a range of ways.
The best way to get more probiotics is to consume them from food sources. That’s because they’re naturally occurring, and they may work better when they’re ingested alongside the other nutrients in the food product. And don’t forget about prebiotics! These are more common in our modern diets and are easier to incorporate into everyday meals – fibre-rich foods like wholegrains, legumes, onions, bananas, garlic, honey, leeks, cashews, and many more.
Consuming a wide variety of foods is a great way to give our gut microbiota a diverse food source and keep them healthy and happy. Eating more foods from traditional cuisine is another way to promote a healthy gut.
Let’s not get fixated on nutrient or food type as the elixir of good health. Instead, enjoy variety, explore new cuisines, and listen to your gut- it’s got a lot to say.
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