How your baby’s gut develops - from the womb through to maturity
Originally, it was thought the gut was pretty void of microbes while in the womb. It was also thought that our babies gut bacteria is entirely influenced by the mother’s own microbiome, as well as the birth process. Research has now demonstrated that our babies are exposed to our body’s microbiome while they are growing in the womb, and that the gut itself is a dynamic and ever-changing entity that is not solely influenced by one moment in time (eg birth).
While it seems everyone has a focus on the gut at the moment (which is great, it’s important!), we need to remember that every organ of our body has a microbial community of its own, and it’s not just the gut that gets colonised. It’s quite amazing to learn that each organ and system needs different microbes to function optimally. And science is only JUST touching the surface on the dynamics between microbes, organs and health. They’re still finding new bugs on the regular and trying to figure out how they fit into the big picture of the human body.
So there is a lot we still don’t know about the gut, especially in a developing baby! However, there are some things that no matter what the science comes up with, tend to remain true. And that’s what we are going to focus on today, because they also happen to be things you can influence!
Stages of gut development for babies
Research published in 2018 described 3 distinct phases of gut development in babies. And while it is a great start, I feel it’s important to highlight that these microbiome tests have some limitations. Firstly, this research was done on babies and children who are at risk of developing type 1 diabetes, as they are trying to figure out if there is a gut contributor. Secondly, microbiome tests are only as accurate as the test, and it is possible that particular species have not been detected in this research. And thirdly, the microbiome is not just bacteria - your body harbours viruses, fungi, parasites and worms.. All of which can be passed onto your body through the birth or your milk, or shared exposures. Nonetheless, I’d love to share with you the three phases this research has come up with because it does correlate with other gut development research.
The three phases:
A developmental phase - age 3 months to 14 months
A transitional phase - age 15 - 30 months
A stable phase - 31 months onwards (ie 2.5 years of age)
They have also detected maturation changes continuing long into the 20 years of age bracket, and research suggests that elderly gut flora begins to change too. So it is likely that the gut is a dynamic, ever-changing being of it’s own.
And this is actually good news, because you can release the guilt you may feel over that dose of antibiotics, or concerns your baby’s c-section has ruined their gut! There is plenty that can be done after one ‘insult’ to the gut balance.
But what I want to highlight from this research is that you can see each window is quite large. There is plenty of time for you to use diet and lifestyle to influence your baby’s gut development, and therefore their whole health!
Influencers of a baby’s gut development
Gut development does not happen in isolation, and there are many factors that contribute to the health of the gut.
Birth process
While some exposure occurs through the pregnancy, the first big exposure your baby receives is through the birth. When your baby travels through the birth canal, or your c-section opening, the resident bacteria (good or bad) colonise their digestive tract. They also colonise your baby’s skin, and start to influence their immune system development.
There has been some evidence to suggest that babies who are born via vaginal birth vs c-section birth have very different bacteria colonise their gut, but that sometimes these differences can be quite short-lived. Those born vaginally tend to be colonised with the bacteria present in the mother’s vagina and digestive tract, whereas those born via c-section generally have more skin-based bacteria. It all comes down to what they were exposed to during the birth process!
Breastfeeding
One of the biggest variances in babies’ gut microbiome are due to whether a baby is breastfed or bottle fed. But here’s the exciting thing - it didn’t matter if your baby was mixed fed breast / bottle, or breast / solids - those benefits were still there. The sad part (for all of us) is that these effects drop off pretty rapidly after breastfeeding ceases.
Breastfeeding increases the number of bifidobacteria in the baby’s gut, which have an important role in appetite regulation, blood sugar balance, and modulating inflammation. It is thought that this is one of the reasons why health outcomes in breastfed babies tend to be higher.
Breastfeeding also stimulates the vagus nerve, which we will touch on further down.
If you’re having difficulty with breastfeeding, please contact a lactation consultant who can support you (if you want to continue).
Nutrition
As we introduce solids, the diversity of the gut flora tends to increase. This is largely dependent on the type of diet we give our babies, and which bacteria they already have in their gut. Basically, our food doesn’t only feed our bodies, it also feeds our bacteria and gut microbiome. Food can be used in a beneficial and gut-supporting way, or in a way that causes ‘bad’ bacteria to overgrow, triggering inflammation and changes in the metabolism of foods/hormones/brain neurotransmitters.
If you’re a regular follower of Fearless Foodies, you’ll know I recommend a particular set of 12 foods to begin with, and all my recipes consider the gut flora as one of many health-influencing factors.
Research tells us that when it comes to nutrition and gut health, there are some simple dietary rules to follow.
Ensure you eat enough fibre
Don’t overdo the sugar (which is essentially food without fibre!)
Eat a large variety of foods (so that you stimulate a wide range of gut bugs to flourish)
Adding a prebiotic supplement into their diet is helpful too (yes prebiotic, NOT probiotic)
Do not introduce food before 4 months of age (the research is very clear on this)
Your baby’s digestive system is just not ready, no matter what anyone tells you
The biggest impact of nutrition during childhood is on our childrens’ brains! Yes, you read that correctly. Not only does early nutrition influence their gut health and microbiome, it also influences their brain health. The foods you give your baby first up have the ability to influence their lifelong appetite, food preferences, and metabolic health - all by changing the brain and how it is wired in those early days.
If you’re interested in going deeper into how food impacts your child’s gut flora and brain health, I’ve dedicated an entire module to it (and it’s interesting stuff!).
Vagus Nerve
The vagus nerve is the longest nerve in the body, and it has a large influence on gut flora, digestion, and overall wellbeing.
The vagus nerve has ‘tone’, which basically indicates how well your vagus nerve functions. So a baby with high vagal tone can have a completely different gut profile as compared to a baby with low vagal tone. This goes for adults too (do a quick google on the vagus nerve and see what comes up for gut health!).
The biggest thing to inhibit the vagus nerve is stress (specifically high cortisol, our stress hormone), so one of the first questions I ask a mother of a new baby in my practice is about the level of stress during their pregnancy. Now, most mums initially say there was no stress, and then reflect, and come back to the second session and say that yes, there was in fact more stress than they realised. Maybe finishing up at work was a struggle, or morning sickness got the better of you, or possibly the pregnancy wasn’t going the way you’d hoped and the labour ended up being stressful for you and your baby. We live in a busy, high stress world without enough rest. And our nervous systems try to adapt to the stress of it (most of the time), but this can have an impact on our hormones and our vagus nerve.
The vagus nerve supports the gut microbiome in 2 important ways. Firstly, it causes peristalsis, which is the movement of food waste through the digestive tract. In a high fibre diet, this peristalsis kind of cleans the gut like a scrubbing brush, inhibiting infections, ‘bad’/opportunistic bacteria, parasites and the like to take a hold on the gut lining and start growing.
Secondly, the vagus nerve contributes to the gut immune system, and can upregulate a response when something foreign or dangerous is detected. This is so important when those little bugs end up bypassing the first step (and when low stomach acid has prevented them from dying higher in the digestive tract), because it means the gut still has a chance to kill these bugs.
Unfortunately, the vagus nerve is sensitive to stress and inflammation, so if nutrition is poor, or there is a high level of stress in the body, this will decrease the vagus nerve’s ability to function fully.
The ways you can best support your baby’s vagus nerve function are:
Plan for a lower stress pregnancy (as possible)
However the birth ends up, it is how we respond to it that causes the stress response - we need to stop putting all this pressure on ourselves, and allow ourselves space to resign to the process
Prepare for your trimester 4 - postpartum is so important and often overlooked
Buy less baby products and put more of your finances towards your own recovery
Establish breastfeeding - this stimulates the vagus nerve
Practice attachment parenting - this also stimulates the vagus nerve
Inflammation and Leaky Gut
All babies are born with a leaky gut; this is part of their immaturity. Just as their brain needs to develop, and their bodies grow, their gut and digestive system also need to develop with time.
But there is a general process that is supposed to happen, and it typically begins around 4 months, and finishes around 5 years of age. Gut maturation leads to less and less ‘leakiness’, meaning that proteins that enter the gut should remain in there and not be allowed into the bloodstream.
This leakiness (and a lack of digestive enzymes) is the reason why you should never introduce solids to your baby before 4 months of age. And while we are on this topic, the foods you give your baby actually stimulate the different sorts of digestive enzymes to be produced, so our baby’s first foods are actually very important for their overall gut health.
The body is sometimes like a double-edged sword, because large undigested proteins in the gut can cause inflammation and leaky gut. But inflammation from other causes (such as a viral infection, or stress) can lead to leaky gut, which can trigger food intolerances. So what comes first? It’s very individual, so there’ll never be one solid scientific answer on that one (in my opinion).
A Healthy Gut from Womb to Adulthood
The goal for me as a practitioner (and why I created Fearless Foodies in the first place) is to help mothers start their baby’s life off on the right foot, with the goal of preventing chronic diseases starting during childhood. Never in the history of the world have our children been so unwell - whether it’s obesity, or airway dysfunction, or allergies and intolerances, or even type 2 diabetes. The list goes on and on. And we as caregivers have the power to change these stats, one child at a time.
When it comes to our babies and their gut development, we need to ensure their gut is developing as healthily as possible (for them). The reality is that the 3 topics we have touched on - breastfeeding, nutrition and vagus nerve function - are the simplest ways you can influence your baby’s gut health, without even having to worry about anything else! And you don’t even have to do them all PERFECTLY. The benefit is in applying these rules as much as realistically possible.
Frequently Asked Questions from this Blog
(added 28/4/21)
I received so many emails and comments from this blog so I’m sharing the most FAQ - hope it helps!
What are common baby digestive problems?
The most common baby gastrointestinal problems are usually due to gut immaturity. Sometimes these can be labelled as colic, reflux or wind. And let me be clear, some babies with these expressions do have additional underlying issues - it is not always gut immaturity that causes them. However what the research indicates is that many babies ‘grow out’ of digestive problems as they get older. This may be related to the progression of gut development to a more mature gut.
Gut health and digestion is a fine balance between many mechanisms. These include the quality of the proteins they are exposed to (even through the milk), how well their stomach acid can function, how much motility exists in their stomach (it can be too high or too low - think reflux vs constipation), whether their immune system is being triggered by a food, how much stress their little system is under (eg. birth trauma, or using cry-it-out methods), and the tone of their vagus nerve. And that doesn’t even begin to cover the gut flora and possible imbalances in that!
If your mother’s intuition is telling you that your baby’s gut is not quite right, it’s best to speak with a professional such as the Fearless Foodies naturopaths.
How do you improve your baby’s gut flora after taking antibiotics?
One of the biggest concerns with giving your baby antibiotics is the gut issues afterwards. Antibiotics generally work by killing a lot of bugs - good and bad. And this is often needed in times of infection - especially in babies when their immune system can’t fight everything on it’s own. So let’s start by releasing the guilt associated with giving our babies antibiotics, if and when they needed them!
The good news is that effects after antibiotics appear to be short-lived. And your baby’s gut can be replenished with good bacteria once again. The best way to do this is via breastfeeding (if you can), probiotics, and also my favourite - prebiotics.
Prebiotics come in the form of food that is high in fibre, mostly vegetables come out on top but fruit also does have some fibre. So if your baby is above 6 months, you can definitely give them fibre in their own meals. You may also like to consider bone broth (check out my recipe here), as well as slow cooked, nourishing, meat and veg recipes.
You can also take a prebiotic supplement. So if you’re breastfeeding, you could take that yourself, and if you are not, you can find one suitable for babies to place in their formula. Even if you are breastfeeding, some directly to your baby may have a bigger impact than via the breast milk.
Probiotics can be given after a round of antibiotics to assist in replenishing the gut microbiome, however generally speaking I don’t suggest these are a daily thing. Try add them in for a month and then stick to the prebiotics.
After antibiotics, it is important to ensure your baby goes back to a well-balanced diet of fat, protein and carbohydrates, and this is where slow cooked meat dishes go down a treat! Or soups too.
Does baby get probiotics through breast milk?
Research has suggested that any proteins the mother is exposed to will be passed through into the milk. This goes for foods, probiotics, viral proteins, and other immune antibodies.
Breast milk is high in bifidobacteria as these are useful for digesting milk, so they support your baby’s gut in being able to convert milk into fuel and nourishment.
However some research on other probiotics has found that yes, they are passed through the milk.
How does a c-section affect your baby’s gut health?
C-section babies tend to have more skin-based bacteria in their gut, as they haven’t been given the opportunity to breathe in the vaginal bacteria as they move through the birth canal.
While this in itself has been linked to outcomes later in childhood, and some mothers have taken to vaginal seeding (swabbing the vaginal area and covering their baby with it to add some of the birth-type bacteria into their baby’s microbiome), a lot of the research is suggesting that you can tip the scales in your baby’s favour quite easily and quickly.
For example, if you look at the things above that affect your baby’s gut development, there is plenty you can do to support it. And it’s all about the 80/20 rule. None of us, not one, can get it perfect, but we can do the best we can with what we’ve got.
What are the signs that your baby is not digesting breast milk properly?
There are many reasons why your baby isn’t digesting breast milk properly and I have touched on them above in the baby digestive problems question.
If you have oversupply, or your baby is only getting the foremilk, they may appear to have explosive poos or pain and wind, but it’s likely just a lactose-overload. This is resolved with feeding technique and as your baby grows older.
Babies who feed frequently for pain or to provide comfort (rather than for hunger) may also appear to have trouble digesting their milk. However, again, it’s because the sucking motion and the feeding gives them some kind of comfort or relief, and so their bellies become VERY full! Just like how we feel when we have eaten too much. I know experts may say that babies can never be full, but it’s just important to bear in mind that sometimes comfort feeding can overload the digestive system.
If your baby is having issues with digesting milk because of a protein they can’t tolerate (eg. gluten or dairy), they may have mucousy poo, seem irritable, and often have skin presentations too like rashes or eczema. I don’t recommend removing foods from your diet while breastfeeding unless you have tried everything else and are absolutely certain it’s the food causing the issue.
