IBS & Anxiety

Does Digestion affect Mood?

Most of us think digestion begins in the stomach but in fact, it starts in the brain and is organised by the nervous system. This is why internal stressors (what we think and feel) and external stressors (what we see or smell) can affect our digestion and how the GI tract (the delivery system from the mouth to the organs and anus) behaves.

Here, I outline some of the ways these system influence digestion and mood.

The Brain

This is where digestions begins. Ghrelin, known as the “Hunger Hormone,” is released in the stomach and sends a signal up to the brain, telling us to get moving and find food. Interestingly, the parts of the brain that help us find food are also the parts involved in movement, stimulation, curiosity, and reward.

Most of us are bombarded with images of tasty food on a daily basis. This is not conducive to a balanced digestive system. When we see or even think about food, the brain tells the rest of the body to prepare for eating. Our mouths salivate. The stomach secretes digestive enzymes, and so on. The body does this because it’s smart and it likes to be prepared.

The brain reads these tasty images as food cues, and prepares the body accordingly. But the constant flow of fake cues hijacks our appetites. Unsurprisingly, most people are out of touch with their natural hunger cycles, meaning they over- or under-eat, or eat at the wrong times, in turn, affecting the nervous system.

The Nervous System

Digestion is controlled by the Autonomic Nervous System (ANS), and has two branches: the Sympathetic Nervous System, and the Parasympathetic Nervous System.

The ANS releases neurotransmitters (hormone-like chemicals) that communicate with organs and the brain, assessing the body’s internal and external environments, and making necessary adjustments or issuing calls to actions. The balance of signals affects the speed at which food moves through the body, absorbs nutrients, secretes digestive juices; and the level of inflammation in the digestive system.

The Sympathetic Nervous System (SNS) responds to intense activity, stimulation or stress, and is more commonly known as the “fight or flight” system. It tends to shut down digestion and appetite. Our mouths may go dry, we don’t want food, the GI tract stops moving food, and the stomach feels tense, or gets “butterflies.”

The Parasympathetic Nervous System (PNS) activates with rest and relaxation. When it’s activated, digestion regulates and food moves through the GI tract steadily and calmly. However, in situations of extreme stress, if the SNS is exhausted, the PNS will kick in. When this happens, it can cause loss of bowel control, or diarrhoea.

The Endocrine System

The endocrine system is a chemical messaging system that identifies changes in the body and releases hormones that tell the body how to deal with the change. It’s tightly linked with the ANS.

The human body circulates around 50 different hormones, and most are produced in the glands, for example, the pituitary, thyroid, adrenals or thymus gland. Hormones are released into the blood stream to activate target cells, and control a large number of the body’s functions including homeostasis, metabolism, sexual activity, and contraction of the smooth and cardiac muscles.

Ghrelin is one of the hormones released by the endocrine system. All hormones play a role in how efficiently the body operates. For example, leptin regulates energy balance in the body. When leptin is high, we’re not hungry. When leptin goes down, we get hungry. But leptin can be suppressed by SNS activity, one of the reasons some people eat when stressed.

The most important hormone at play for women is oestrogen, the principal growth hormone for reproductive organs. But that’s not all it does. Oestrogen plays an important role in the development of the brain, cognitive function and blood flow. It also influences the release of serotonin, dopamine, epinephrine, norepinephrine, and adrenaline, affecting mood.

Gut-Brain Axis

The nervous system also has its own localized nervous system known as the Enteric Nervous System (ENS) and communication between the ANS and ENS is a two-way street, busier than a trending topic on Twitter. Think of the ENS as mission control. It’s in charge of physiological emotional state, constantly assessing our wellbeing in relation to our environment. In other words, it’s where your “gut feelings” happen.

The ENS is made up of approximately 100 million nerve cells in and around the GI tract. It takes messages from the SNS and PNS but can also operate independently of them. It’s also in constant communication with millions of immune cells, surveying the GI tract for bloating, inflammation or infection.

Because the connection between the gut-brain axis (GBA) is so strong, and the communication flows both ways, your external environment has profound effects on your internal state. Stress, sadness, loneliness or any other negative emotion will impact the effectiveness of your GI tract, either slowing down or speeding up the movement of food, and disrupting the pathways of microbiota, leading to nasty GI symptoms like bloating and cramps and worse.

The Microbiome

The microbiome is the collective community of bacteria living in the body, while specific communities are called microbiota. They make up two-thirds of the human body. If your body is not working in harmony with its microbiome, it will affect your digestion, mood, fitness, and overall health.

The microbiota in your stomach is effectively a parasite but it maintains a harmonious relationship with you, its host, through the synergistic digestion of food. Intestinal bacteria ferment dietary carbohydrates such as fibre, oligosaccharides and sugar (lactose and sugar alcohols) that the small intestine can’t digest on its own. In this way, it cleans the body, mopping up any undigested nutrients.

That’s not all they do. They prevent harmful bacteria and yeast from colonizing the gut. They remove carcinogens and boost the immune system. The regulate inflammation, hormone responses, levels of body fat, nervous system function, and mood.

A balanced diet doesn’t just include food to feed you, but also food to feed the microbiota. Probiotics are foods like kimchi that contain bacteria. Prebiotics give the bacteria stuff to eat, examples include bananas, asparagus, onions, leek, garlic, barley, oats and apples, foods most women with IBS can’t eat.

Back to IBS and Anxiety

As you can see the links between the gut and your emotional state are profound. Yes, what you what you eat affects your mood. But more than that, where you eat, when you eat, how you eat, why you eat, who you’re eating with or who you’re not eating with all affect your digestion, which in turn affects your mood and overall wellbeing.

If you’re anxious, it’s going to upset your stomach. If you’re stomach is upset, it’s going to affect your nervous system. If you’re nervous system is faulty, your microbiota may start rioting, disrupting hormone responses, causing inflammation, or worse, infection, making you sick, and more anxious. Do you see the cycle?

There is a way to break the cycle. It starts with learning how to listen and connect back to your body’s natural hunger signals.

If you would like more information on how to do this, click HERE or contact me at wildwomanaw@gmail.com


How is your environment? Do you have a quiet space where you can switch off, tune out, take time to centre yourself? If you do, do you spend time there? If you don’t, how can you create one? What is your ideal quiet space? Describe it.

Published by The Healthy Hashhead

Challenging attitudes to cannabis, nutrition and fitness with conscious questions.

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