By Abigail Attenborough , MSc Nutrition
What is the gut-brain connection?
As talk around the gut becomes more commonplace, you may have heard of the ‘gut-brain-axis’, or the ‘gut-brain connection’. More and more research is becoming available that is highlighting the importance of the communication between your brain and your gastrointestinal (GI) tract. Think of this connection like a ‘superhighway’ linked by something called the vagus nerve. The vagus nerve is the longest nerve in the body, affecting multiple organs and nearly every part of the body. It interacts with the parasympathetic (your ‘rest and digest’ nervous system) control of the heart, lungs & digestive tract.
How can the gut-brain connection affect mental and brain health?
Research suggests the vagus nerve can change the composition of our gut, and that alterations and/or dysfunction in the gut causing low vagus function, may be important in the pathophysiology of eating disorders, low mood disorders such as anxiety and depression, irritable bowel syndrome (IBS) and addictions.
Our GI tract is populated with good and bad bacteria - this is called the microbiome. Both this good and bad bacteria should be balanced out to work together in symbiosis - harmoniously. Overabundance of some microbes however, can resort to common psychological disorders such as depression, anxiety and OCD, as well as inflammation of the GI tract causing gastrointestinal disease such as IBS and Crohn’s disease.
The gut-brain connection is demonstrating that the microbes in our GI tract can vastly effect the way our brain and enteric nervous system (ENS) governs the function of the GI tract. Scientists like to call the ENS our second brain, as it main role is to control digestion. An example of this bidirectional pathway between your gut and the brain can be illustrated by the fact that more than 50% of patients with IBS have anxiety or depression or similar mood disorders.
The gut and brain are also connected through chemicals called neurotransmitters such as serotonin and GABA (gamma-aminobutyric acid), which contributes to feelings of happiness. In fact approximately 70-90% of serotonin comes from gut. Having a wealth of good bacteria can help promote wellbeing, relaxation, and feelings of reduced anxiety by releasing GABA in the brain. Researchers now say that the role of promoting good health should extend to include the health of your brain and neurological systems, and current understanding is that this may be associated with alternations in the microbiome.
What can you do to maintain or restore the health of your microbiome for better mental health?
Our microbiome needs to be fed in the right way: you are what you eat, literally. Eat foods that sooth, nourish and heal the gut such as the suggestions below.
A diet that includes foods with probiotic and prebiotic ingredients. Probiotic foods contain live beneficial bacteria and include plain yogurt (if you can tolerate dairy), kefir (fermented milk drink similar to a thin yogurt), cottage cheese, fresh raw sauerkraut, kimchi, kombucha, beet kvaas (similar to kombucha), apple cider vinegar, natto (fermented soy beans), and miso. This is not new knowledge; kefir dates back many centuries to the shepherds of the Caucasus Mountains. Keep in mind that the probiotic effects of these foods are destroyed by cooking, processing, or preserving at high temperatures and thus most need to be kept in the fridge. Prebiotic substances are specific types of indigestible fibre that nurture the growth of probiotic bacteria. They do not contain living organisms, and are consumed by probiotics. Prebiotic foods include artichokes, leeks, onions, garlic, chicory, cabbage, asparagus, legumes, and oats. One study found that taking a prebiotic called galactooligosaccharides for three weeks significantly reduced the amount of stress hormone in the body, called cortisol. Another small study of people with IBS and mild-to-moderate anxiety or depression, found that taking a probiotic called Bifidobacterium longum NCC3001 for six weeks significantly improved symptoms.
Other food groups specifically beneficial for the gut-brain connection are: Omega 3’s such as oily fish, flax seed, and chia seeds; high-fibre foods such whole grains, nuts, seeds, fruits and vegetables. These all contain prebiotic fibres. Try to consume plenty of soluble fibre and resistant starch in particular. Soluble fibre promotes the survival of beneficial gut flora and can have a soothing effect on the gut; this is because it dissolves in the body and creates a gelatinous structure as it passes through the GI tract. Starches such as sweet potatoes, white potatoes, plantain, taro, and green banana flour are particularly good sources of resistant starch, and well as lentil and beans which are also soluble fibres.
Polyphenol-rich foods such as cocoa, green tea, olive oil and coffee all contain polyphenols, which are plant chemicals that are digested by your gut bacteria. Polyphenols increase healthy gut bacteria and may improve cognition. If you’re reaching for dark chocolate to get your polyphenol hit, ensure it is above 70% cocoa. Serotonin boosting foods are important to help stabilise ones’ mood. These include eggs, (especially the yolk), salmon, nuts and seeds. Tryptophan is an amino acid that is converted into serotonin. Foods that are high in tryptophan include turkey, eggs, cheese and soy products such as tofu - many protein-based foods. Try and consume bone broth daily, whether as a stock or mixed with hot water to make a tea. It’s rich in glycine and gelatin, bone broth helps restore the integrity of a damaged gut barrier.
Lastly, it's important to mention that probiotic supplementation is still being disputed in science papers. Researchers have yet to determine which bacterial species or combination of species, doses and delivery systems can best help treat specific symptoms and maintain overall health. It is still unclear whether single strains of probiotic bacteria are as effective as mixtures of different strains, and if or how any combination of bacteria in a supplement can interfere with other medications or other aspects of health.
Nevertheless, following the guidance above and generally eating whole foods and reducing processed food is a great way to promote gut health!
By Abigail Attenborough, a Nutritionist and Personal Trainer with first class degree in MSc Nutrition and undergraduate degree in Biology with an earnest passion for brain nutrition and weight regulation research. You can find Abby on Instagram @abbyfit_
References
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