How Your Child's Gut Health Drives Anxiety & Mood

If your child has both a worried mind and a wobbly tummy, then there could be a close connection. This is because their gut and their brain talk to each other constantly, and when the gut is inflamed or harbouring the wrong bacteria, the brain feels it and your child’s anxiety spirals. In my 30 years of clinical work, I have found that sorting out the gut is often the single best way to move the needle for anxious kids and teens. This blog explains why, and what you can do as parents, to help them feel calm and safe.

In the first part of this blog series, I walked you through the key nutrients and habits that calm an anxious child. This part 2 digs into the lesser-known gut–brain axis and how the trillions of microbes living in your child’s intestines can shape their mood, and what you can do about it. Look out for part three all about deeper immune and metabolic drivers of anxiety.

If your child is anxious and has any tummy symptoms such as bloating, tummy pain, constipation, loose stools, nausea, picky eating or sugar cravings, then read on. There is a very good chance that their gut is part of their anxiety story.

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Why the gut talks to the brain

There are around 100 trillion microbes living in your child’s gut, mostly in the large intestine. Together, they make up the gut microbiome and do far more than just digest food. They are the building blocks for neurotransmitters such as serotonin, dopamine and GABA via the food your child eats. The friendly microbes regulate inflammation, and they help the immune system recognise what is safe and what is harmful. These good bacteria even influence a child’s appetite and mood through a network of signals called the gut–brain axis.

There is a superhighway linking your gut and your brain called the vagus nerve, which runs from the brainstem down to the gut and back again. Research finds that 80 to 90% of vagus signals go from the gut to the brain, and only a mere 10% go from the brain to the gut. So, the gut is doing most of the talking, and the brain is doing most of the listening.

GABA is the neurotransmitter that keeps a child feeling safe and calm. Animal studies have shown that specific microbial strains can change GABA receptor expression in the brain. And some friendly strains can reduce anxiety-like behaviour, but only when the vagus nerve is intact. If you physically cut the vagus nerve (Don’t try this at home… but it’s been observed in studies!), the calming GABA effect disappears, providing evidence that what happens in the gut directly shapes how the brain handles stress.

The neurotransmitters your child’s gut bacteria make

The friendly bacteria in the gut are little neurotransmitter factories. For instance, lactobacillus and bifidobacterium species which you often find in live yoghurt, kefir and biotic supplements help to produce GABA. The friendly bacterial species within the Escherichia, Streptococcus, and Enterococcus families produce serotonin.

Other gut bacteria make short-chain fatty acids (especially butyrate, which you can also get from eating butter and ghee) that nourish the gut lining, dampen inflammation and influence brain function. When the right bacteria are found in good numbers within the intestines, your child has a much better chance of feeling calm.

When the microbiome is depleted or out of balance, this whole production line falters. This might be due to taking antibiotics or reflux medication, chronic stress, a diet full of ultra-processed ingredients and not enough fibre or fruit and veg or even a nasty gastrointestinal infection. A depleted microbiome means that the gut produces less GABA and serotonin and more inflammatory signals, and the brain ends up running on anxiety. Studies consistently link gut dysbiosis with a higher likelihood of anxiety and depressive symptoms in both children and adults.

When the ‘wrong’ bacteria take over

It is very common and easy for the ‘wrong’ bacteria to populate in a child’s gut. This imbalance is known as dysbiosis, which simply means that there are too many of the bad guys and not enough of the good guys living in the gut microbiome. The helpful, friendly species usually include microbial strains such as Lactobacillus, Bifidobacterium, Akkermansia and Faecalibacterium. The bad guys are usually inflammatory or neurotoxic (detrimental to the neurological system) and include certain strains of Klebsiella, Citrobacter, Proteus, Pseudomonas, Clostridia, or yeast overgrowth like Candida albicans.

Causes of this dysbiosis are similar to microbiome depletion and include frequent courses of antibiotics in early life, a diet very low in fruit, veg, pulses and seeds, kids hooked on fibre-free ultra-processed food, chronic stress, and a birth history of C-section without skin-to-skin contact or breastfeeding. None of these is anyone’s fault, and most can be worked around with professional support from our gut health specialists.

Why are these bacteria a problem? Inflammatory bacteria in the gut microbiome can release toxins called lipopolysaccharides (LPS) that can leak through the gut wall into the bloodstream when the gut lining barrier is compromised. This is called gut permeability or leaky gut (see more further down). From there, they trigger low-grade inflammation throughout the body, including the brain and nervous system. Research links this kind of inflammation directly with anxiety, low mood and brain fog in both kids and adults.

When gut bacteria grow in the wrong place

Small intestinal bacterial overgrowth is also known as SIBO. This is where the bacteria that should mostly live in the large intestine ends up colonising the small intestine by mistake. These misplaced bacteria then cause bloating, gas, tummy pain, nausea, fatigue and a long list of food intolerances from gluten, to dairy to broccoli to garlic. SIBO is also closely associated with symptoms of irritable bowel syndrome (constipation, loose bowels, bloating, gas and pain) and is increasingly recognised in children and teenagers as well as adults.

SIBO really matters for an anxious child because it drives inflammation in the small intestine, where most nutrient absorption happens. So, when SIBO is present, children often become deficient in iron, vitamin B12, vitamin D, magnesium and zinc which are important nutrients for mood, focus and nervous system regulation. .

Classic clues that SIBO might be in the picture include bloating above the tummy button that worsens as the day goes on. You might also spot burping or reflux soon after eating, or a child who feels worse after eating “healthy” foods like onions, garlic, apples or beans, and a long history of antibiotic use or low stomach acid.

Leaky gut and inflammation

The gut lining is only one cell thick and a remarkable barrier between the outside world (the inside of your gut is technically outside your body) and your bloodstream. These tight junctions between the villi in the small intestine act like security guards, deciding what passes through and what stays in the gut. When dysbiosis, food sensitivities, stress or infection irritate the small intestine lining, those tight junctions loosen, and that is when intestinal permeability can become an issue. This is often called leaky gut.

Once unwanted partially digested food particles and bacterial fragments from the small intestine slip through these tight junctions, the immune system raises the alarm. This then sets off an inflammatory cytokine storm which circulates in the blood and can cross the blood–brain barrier. This in turn can affect a child’s mood and sleep, and drive anxiety and that horrible feeling of being unsafe.

Which gut clues to look out for

Most parents miss the gut signs in an anxious child because they look so ordinary and are often played down by medical professionals. Here are the signs to look out for if you have an anxious bunny on your hands and you want to work out if there is a gut connection:

Bloating, particularly after meals, or a tummy that is flat in the morning and looks like a balloon by the evening
Constipation or pebbly bowel movements
Loose stools – think splatty or cow pats
Tummy pain or feeling sick, especially before stressful events
Sudden onset of food fussiness – a narrowing of their diet
Strong or insatiable sugar and carb cravings
Bad breath or a coated tongue
Dark circles under the eyes
Frequent infections and poor immunity
A history of antibiotics, especially several courses in the first few years
Reflux, burping, or feeling full very quickly

Any combination of these symptoms alongside anxiety is worth taking seriously, and we can run a comprehensive gut microbiome and gut function test to understand if this is something to focus on during your journey to help your child feel calmer and less overwhelmed.

Feeding a calmer microbiome

When supporting the gut microbiome and helping to create a healthy environment in the intestines, it is important to nourish your child’s biome with the best quality food you can, focusing in on foods which are colourful, fibrous and help to cultivate an abundance of friendly bacteria.

Eat the rainbow

Feeding your child a variety of different fruits, vegetables, wholegrains, pulses, nuts and seeds is one of the best ways to also feed a healthy microbiome. Different fibres feed different bacteria and so do your best to feed your child a wide range of plant-based foods, where possible. If they are not keen to eat that many fruits and veg, then smoosh, grate and blend them into foods that they will accept, from pasta sauces, to brownies, to muffins and even waffles. This is something I focus on a lot in my cookbooks too; the recipes really help navigate the variety the gut needs.

Add fermented foods

Fermented foods are part of many cultures throughout the world because they help to enhance the gut microbiome with live and beneficial microbes. Studies suggest that even small amounts of fermented foods can support a child’s gut health and these may in turn help with their anxiety and mood symptoms.

The easiest ones for kids to consume are live yoghurt, milk kefir (try it in a smoothie if eating it straight is too sour), water kefir and small amounts of sauerkraut or kimchi or miso. Apple cider vinegar in dressings and pasta sauces all help.

One top tip is to stir local or raw honey into the yoghurt or kefir as it can help to bolster the gut microbiome more than yoghurt or kefir on its own.

Cut back on UPFs

Ultra-processed foods (UPFs), especially those high in emulsifiers such as lecithins, polysorbates and carrageenan, have been shown in research to disrupt the gut microbiome and increase the leaky gut. Equally, the emulsifier dipotassium phosphate is added to plant-based milks, and the preservative calcium propionate is added to bread. These ingredients are all thought to be inflammatory to the gut and may contribute to dysbiosis, with bad bacteria thriving on them.

The other issue is that eating too many UPFs can crowd out the potential to eat enough fibre-rich foods such as wholegrains, beans, pulses, fruits and vegetables, which are needed to feed your child’s beneficial bacteria.

You do not need to feed your child the perfect diet all the time. Ideally, aim to feed them real food at least 80% of the time, and let processed foods be the exception when out and about or at parties.

Consider targeted friendly bacteria

A good live bacteria supplement can be very useful, especially after antibiotics or for a child with longstanding gut symptoms. It is also a helpful option if part of their anxiety means that they are a fussy eater and will not eat a wide range of fruits and vegetables or fermented foods.

Strains with the most evidence of helping to alleviate anxiety symptoms include Lactobacillus rhamnosus, Lactobacillus helveticus, and Bifidobacterium longum. So look out for products that name the strain on the packet. Around 10 billion CFU is a sensible starting dose for school-age children and teens, while university-aged youngsters can have around 25 billion.

Support the vagus nerve

The vagus nerve responds to fun and calming activities and will work better if you teach your child how to look after it well. Ways to support a healthy and well-functioning vagus nerve include slow breathing, humming, laughing, singing, gargling and gentle yoga. Being outdoors in nature, especially walking through woods, can really help to tone the vagus nerve.

All of these microhabits stimulate the vagus nerve and help to shift a child’s nervous system towards feeling calmer. These daily habits cost nothing and can work beautifully alongside the nutritional and gut health work.

Round up

The gut is where so many anxious children’s stories really begin, and is one of the most important aspects to consider if your child is locked into anxiety or constantly ruminates about the past.

If your child has taken multiple courses of antibiotics, lives with persistent gut symptoms, or anxiety that has not shifted with the basic nutrients shared in the first part of this blog series, then it is worth getting deeper laboratory testing. At NatureDoc we use gut microbiome stool tests, organic acids testing (which can flag yeast and bacterial overgrowth), and SIBO breath tests where indicated.

If you are not sure where your child stands with their gut health, get in touch with our NatureDoc clinical team. We will work through their clinical picture with you, run the right tests, and put a clear health plan in place. Most anxious kids with an underlying gut issue show good improvement within 8 to 12 weeks of focused work, and the rest of the healing journey follows on from there.

This is the second of a series of blogs on anxiety. I have written about the nutrition basics that help anxious kids feel safer to help you lay the foundation for this gut health work. And part three shares some of the more complex drivers of anxiety.

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How kids’ tummy health affects their brains and anxiety