Have you experienced “butterflies in your stomach” or just had a strong “gut feeling” in difficult situations? There’s a good reason why these terms came about – the gastrointestinal tract is inextricably linked to the brain, and stresses from the environment can send signals from the brain to the gut and vice versa, which produces these physical symptoms of the digestive system. This is why you often feel the need to go to the toilet when you are nervous or anxious about something.
Recently, studies have shown that the trillions of microbes in the gut can affect gut-brain connection, and is associated with diseases like Alzheimer’s and autism. Let’s take a closer look at how your gut affects your brain health.
What is the gut microbiome?
In our gut or digestive system thrives trillions of bacteria living together, collectively known as our gut microbiome.
A healthy gut microbiome depends on the diversity of the bacteria there. The greater the diversity, the stronger our digestive system and immunity. Having low gut microbiome diversity is associated with many chronic problems such as:
- Type 1 and Type 2 diabetes
- High cholesterol
- Colorectal cancer
But how can we tell how healthy our gut microbiome is in the first place? Simple — through a poop test. Recently, I wrote an article on what your poop colour, texture and bowel frequency says about your health. It turns out we now can extract DNA from your poop to do gut microbiome sequencing.
Let’s take a look at this particular young lady’s results. The diversity index in this chart refers to the variation of the different bacteria in your gut. The more diverse the bacteria are from one another, the better your health will be.
Her diversity score is pretty low, but was what I expected due to her unhealthy diet which consisted of little food variety and an abundance of processed food.
Does this sound like you? It might be high time to reevaluate your diet!
How does the gut affect the brain?
Ever felt “sick to your stomach” during a nerve-wracking situation? This feeling is possible due to the gut-brain axis.
The gut-brain axis describes the two-way communication between the gut and the brain, and this connection happens with the help of chemicals like serotonin and gut hormones.
Chemicals called neurotransmitters are used by the brain to communicate and control our emotions. Many of these neurotransmitters can be produced by gut bacteria. One such chemical is serotonin with widespread effects on many aspects of your body. It controls bowel movements and the body clock. Most importantly, it also regulates feelings of happiness – mood disorders like anxiety or depression stem from low levels of serotonin.
Another neurotransmitter, GABA (gamma-aminobutyric acid), is able to have a calming effect on the body, reducing fear and anxiety.
Let’s take a look at the aforementioned patient’s GABA score — thankfully she’s in the average range, which means her body can produce sufficient GABA naturally. But I think this could be improved with some tweaks in her diet.
How do I fix my gut microbiome?
Spinach is a vegetable packed with GABA and nutrients essential for the production of GABA. Add spinach into your soups, salads or stir-fries to give you that added dose of GABA you need.
Avoid high-fat foods
A high-fat diet may reduce GABA production. Avoid trans-fat and saturated fat that may contribute to low GABA production and weight gain. However, it is still essential to consume healthy fats like olive oil, avocado and nuts – the key is moderation. A simple way to determine how much fat you need is this – the average person who weighs 60kg can eat up to 60g of healthy fats for a well-balanced diet.
Fruits and vegetables
We need about 400g of fruits and vegetables for dietary fibre and prebiotics that feed the GABA- and serotonin-producing bacteria for good gut health.
Soybean sprouts are full of GABA and a great source of protein and fibre while containing few calories. Add them to your noodles or stir-fry them for a healthy meal.
Pu-Erh is a kind of fermented tea with high amounts of theanine which help improve digestion and fat breakdown. It also contains probiotic strains of Bacillus that help to enhance your gut microbiome diversity, helping to maintain good gut health and digestion.
Yoghurt, kefir, sauerkraut and cheese are fermented foods that contain healthy microbes such as lactic acid bacteria which can improve gut digestion, heart health and brain activity.
High-fibre foods such as whole grains, nuts, seeds, fruits and vegetables have prebiotic fibres that are beneficial for gut bacteria and can also reduce stress hormones.
Polyphenols are plant chemicals that usually have distinct smells, digested by gut bacteria. They increase healthy gut bacteria and may improve cognition.
Tryptophan is an amino acid that can be used to make the neurotransmitter serotonin, thereby improving your mood. Foods high in tryptophan include turkey, cheese and eggs.
How else does my gut affect my brain health?
Your gut has millions of microorganisms, some of which are grouped into major components.
In the interest of this article, I’d like to focus on 2 particular bacterial groups: Firmicutes and Bacteroidetes.
Firmicutes and Bacteroidetes are two bacterial groups you should see a lot of in your gut. The ratio between the two has been associated with depression, Alzheimer’s and even autism in children. This is because both bacterias are anti-inflammatory, and chronic inflammation has been linked to brain conditions.
Firmicutes are more efficient than Bacteroidetes at extracting energy from our food, which means we may absorb more energy than we actually need. Hence, if your ratio of Firmicutes to Bacteroidetes is too high, there would be increased fat absorption and conditions like obesity. So, a healthy Firmicutes-to-Bacteroidetes ratio is essential.
This ratio also explains why some people don’t gain weight that easily – if the proportion of Bacteroidetes is higher, it means we take up less fat and hence fewer calories from the food we eat, making us slimmer and less likely to be obese.
What is the connection between gut microbiome and autism?
Studies show that people with Autism Spectrum Disorder (ASD) have a distinct gut-bacterial profile different from people without the condition. For example, they may have a lower than usual amount of Actinobacteria. Gastrointestinal symptoms like abdominal pain, diarrhoea, constipation and gas are also very common in people with ASD. However, the cause and effect relationship between these symptoms and ASD is not yet proven.
Some studies show that Microbiota Transfer Therapy (MTT), where healthy bacteria are transferred to the patient’s gut, helped to improve ASD-related symptoms. These improvements were seen along with an increase in bacterial diversity in the gut.
All of these suggest that ASD symptoms could be related to the gut microbiome, but we are still in the process of determining the true relationship between the two.
How can I find out what my gut microbiome is?
You can easily find out your gut microbiome through a simple poop test by Bio+Me, a gut microbiome sequencing service by AMILI. Below is a sample of how the poop collection kit looks like — it is a simple, fuss-free process that most patients can carry out easily.
If you’re interested in getting one, these kits can be found at my clinic and my team at G&L Surgical would be happy to assist you in the process. A comprehensive report that summarises the details regarding your gut microbiome diversity and what foods you may take to improve your gut health will also be provided.
I recommended testing your microbiome again 3-6 months after changing your diet.
To good health!
- Willyard, C. (2021). How gut microbes could drive brain disorders. Nature, 22-25.
- Garcia-Gutierrez, E., Narbad, A., & Rodríguez, J. M. (2020). Autism spectrum disorder associated with gut microbiota at immune, metabolomic, and neuroactive level. Frontiers in Neuroscience, 14, 1072.
- Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of gastroenterology: quarterly publication of the Hellenic Society of Gastroenterology, 28(2), 203.
This article was written and medically reviewed by Dr. Ganesh Ramalingam, M.D.