What is the Gut-Brain Axis?
To understand the connection between your gut and your brain, think of a time when you felt nervous – before a presentation or a date, perhaps. Chances are, you felt butterflies in your stomach, nausea, or even diarrhoea. You may also have recognised having a ‘gut feeling’ about something. That was your brain sending signals to your gut. However, most of the signalling is actually going the other way, from gut to brain.
The gut-brain axis is essentially a complex two-way communication between the Central Nervous System (the brain and spinal cord) and the Enteric Nervous System (the gut or gastrointestinal tract). This communication happens via the Vagus nerve, a long bundle of nerves that connect the brain stem to all organs in the body.
How Does the Gut Affect Health & Development?
The health of the gut is inextricably linked to the health of the bacteria within it. Trillions of microbes – bacteria, fungi, parasites and more, collectively known as microbiota – live inside our guts. These help us to digest food and extract the nutrients needed to grow and develop, and also play an important role in the communication between brain and gut. When these bacteria are off-kilter or out of balance, it can affect physical health and brain function.
Bacteria begin to colonise the gut whilst we are still in the womb. The bacteria get a boost at birth and then through breast feeding. Interestingly, the brain and gut bacteria develop together from the first few months after birth until three years of age. Both early-life microbial colonisation and brain development share critical periods of growth, during which time there is extensive messaging between the two.
Ensuring a healthy balance of gut bacteria is therefore critical for childhood growth and development, and for general wellbeing throughout our lives. Some of the ways the gut microbiota affects our overall health include:
Brain development: Gut bacteria stimulates production of brain-derived neurotrophic factor (BDNF), a chemical involved in brain development. Low levels of BDNF have been associated with autism.
Serotonin: Scientists now know that 95% of the serotonin – the mood regulating chemical – we have is made in the gut. There is therefore a direct link between poor gut health and depression. Serotonin also affects pain sensitivity, bowel movements and appetite.
GABA: Another neurotransmitter produced by gut bacteria is GABA, which helps us deal with stress and anxiety and prevents over-stimulation, such as ADHD.
Digestion: The gut microbiome breaks down undigested food, allowing the nutrients to be used throughout the body for growth and maintenance.
SFCAs: Gut bacteria produce compounds called Short Chain Fatty Acids, which are used as fuel by the gut cells. They also enhance mineral absorption – important for growing kids – and promote brain health.
Vitamins: The gut microbiota produce vitamins K and five B vitamins, all essential to brain health.
Immunity: Between 70% and 80% of the immune system is located in the gut. The gut microbiota create a mucus layer which serves as a barrier, preventing pathogens, or harmful agents, from entering the bloodstream. They also stimulate the immune system to keep it strong.
Foods to Keep the Gut & Brain in Good Shape
A healthy gut = a healthy brain.
A number of factors including stress, a diet high in sugar, insufficient fibre, and antibiotic use can disrupt the balance of the microbiota. This in turn can impact the gut’s ability to absorb nutrients, leading to poor growth, development and a poor environment for proper brain function.
Poor gut health can trigger or worsen symptoms of anxiety, obsessive-compulsive disorder, attention-deficit disorder and autism, as well as childhood asthma, allergies and irritable bowel syndrome.
So, what can you do keep your gut and its bacteria happy?
Get those veggies in: Vegetables not only contain antioxidants to keep the immune system strong, but they are also rich in fibre, which is the food of gut bacteria. And when bacteria are well fed they help the brain grow.
Eat good sources of protein: Protein is made up of amino acids, which are the building blocks of neurotransmitters, needed for healthy brain function. Good sources include: fish, such as salmon and sardines, eggs, grass fed beef and wild game.
Fill up on fermented foods: Kefir, sauerkraut and tempeh are a great source of bacteria – although they are not suitable for those with a histamine intolerance.
Consume good fats: As the brain is largely made of fats, it is essential to eat good fats to support proper cognitive function and growth. Sources include: oily fish, eggs, avocado and extra virgin olive oil.
Avoid Allergenic Foods: Continuously eating foods that are creating an allergic reaction will lead to inflammation in the gut and prevent proper absorption of nutrients. Common allergenic foods are gluten, dairy and soy.
A number of lab tests are available for both adults and children with gut issues, that can help to identify underlying causes and design a tailored treatment plan. Almost every dietician, doctors clinic and laboratory in Cayman offer a variation on the tests suggested below. Some of these tests are performed at local labs and some send the tests away for analysis abroad.
Ova & Parasite Test and Stool Culture Test: This is a basic stool test which doctors will recommend if they want to check for parasites and pathogens.
GI-MAP: This is an even more advanced stool test which is used to detect parasites, bacteria and fungi. It can also assess good and bad bacterial status and overall gut immunity. This test must be special ordered by a doctor or dietician.
OAT (Organic Acids Test) or Amino Acid Profile: A simple urine test which assesses neurotransmitter production, bacterial overgrowth, as well as oxalates – which have been shown to impact children with learning challenges. This test needs to be ordered from overseas by a doctor or dietician.
Urine Culture or Urinanalysis Test: Almost any laboratory in Cayman can do these two tests. The tests are used to determine if you have a urinary tract infection or kidney function problems. If there is a bacterial growth in the culture, it is identified and tested against antibiotics to see which ones are suitable for treatment.
Micronutrient Testing: With a simple blood test all doctors’ clinics can measure iron, vitamin levels such as vitamin D and vitamin B12 and folic acid levels to name a few. Some of these tests are done at laboratories on-Island and some are sent overseas for testing. Doing a full comprehensive profile of all the main vitamins, minerals, antioxidants, fatty acids, amino acids and your ability to metabolise carbohydrates is less common. A dietitian can conduct this test and samples will be sent overseas for analysis.
Food Sensitivity/Intolerance Testing: Almost all dieticians and many doctors clinics in Cayman can test which foods are well tolerated by an individual and which are not. There are different types of tests that can be done. Immunoglobulin E (IgE) test, ALCAT Testing, MRT Mediator Release Test. IgE testing is an immune response to a particular allergen that can cause anaphylaxis, and in some cases it can be life threatening. An example of this is an allergy to peanuts or shellfish. ALCAT and MRT testing is used for food sensitivities that are not life threatening but can cause irritation in the body resulting in digestive problems, stomach cramps, tiredness and migraines to name a few of the symptoms.
Nutrigenomix Testing: This saliva test can help determine your risk for vitamin deficiencies, your sensitivity to caffeine, alcohol and gluten, and amongst other things, it can advise on how much omega fats you need to consume to maintain “good” HDL cholesterol levels.
Tips for Picky Eaters
Increase kids’ protein intake by adding a scoop of protein powder to smoothies, pancakes or porridge.
Wean little ones off foods they are intolerant to by slowly mixing in the new with the old. For example, start mixing a small amount of non-dairy milk with regular milk, increasing the amount only after a few days, until they become accustomed to the dairy alternative.
For kids who aren’t getting a wide variety of foods in their diet, supplements may be recommended. The most common ones needed for healthy gut and brain function include: vitamin D, zinc, magnesium and omega 3 fatty acids. Butyric acid supplementation has been found to be helpful for hard, large stools.
Nutritional Case Study on Autism
A 2019 study supports what nutritionists and parents have been witnessing in practice for years: that diet and nutrition can have an impact on mental health. The paper, titled Comprehensive Nutritional and Dietary Research Study for Autism, followed 117 individuals, aged 3 to 58, 67 of whom had an ASD diagnosis for one year. The subjects were given a gluten, dairy and soy-free diet, rich in essential fatty acids, multi-vitamins and minerals. They also took carnitine and Epsom salts baths. The results showed considerable improvements in cognitive function and development, with a reduction in depression, anxiety, tantrums and improved sociability. Gastrointestinal symptoms such as constipation and diarrhoea disappeared. There were three exceptional cases of note: Boy (7) Pica (a type of eating disorder) was completely resolved. Girl (9) no longer required a wheelchair after the carnitine supplementation was added, and a man (27) with a history of severe urinary retention requiring catheterisation could urinate on his own.
Please note that you should consult with your doctor or dietitian before considering such a change to your or your child’s diet.
Glossary Of Terms
Enteric Nervous System (ENS) Also called ‘The second brain’, it controls the functions of the GI tract.
Microbiota/Bacteria The collective term for trillions of microbes that support gut function. Made up of a combination of bacteria, fungi, viruses and protozoa it weighs up to two kilograms.
Neurotransmitters There are over 40 and these are produced in both the brain and gut where they transmit signals that balance mood and mental function.
Probiotics Live bacteria and yeast which can help to restore a healthy gut microbiota balance.
Prebiotics Dietary fibre which feeds the beneficial bacteria in the gut. Found in a variety of fruits and vegetables.
Vagus Nerve Long and wandering, it’s the main pathway along which the gut-brain cross-talk occurs. It is through this connection that the gut microbiome can influence mood, stress and overall inflammation in the body.
About the Author
Kerry Fugard, from Nutri 360, is a Nutritional Therapist with previous experience as a counsellor. She has a practice in Geneva, Switzerland, and online, using the tools of Functional Medicine to help her clients of all ages get to the cause of their health concerns and assist healing through targeted nutrition. Her specialising areas are gastrointestinal disorders, hormone and mental health.