The vagus nerve is the biggest nerve in the body, travelling through the brainstem, the neck, the thorax and into the lower abdomen. It is part of the parasympathetic nervous system, and its job is to control automatic processes.

For every ‘output’ fibre there is from the brain through the vagus to the body, there are nine ‘input’ fibres back to the brain, telling the brain what is happening in the gut. The vagus nerve senses what is happening in the gut, and tells the brain.

In babies, the vagus nerve is associated with learning to swallow properly (milk or food), digest food properly (without colic, reflux or constipation), and also to be happy and content when not eating (it is a calming nerve).

Many practitioners are missing the link between vagal tone and a baby’s health outcomes, however there are many studies in adults indicating high vagal tone is associated with health and longevity.

What is vagal tone?

Vagal tone basically refers to the ‘strength’ of the vagus nerve. High vagal tone is considered a good thing, and low vagal tone may present with colic, reflux, irritability, food reactions, and poor sleep.

The biggest cause of low vagal tone is chronic ‘stress’. And remember, our babies nervous systems are primed for life while they are in the womb. So if your baby is grown in a stressed out body, it’s nervous system is primed for stress, before it even enters the world. That’s not to say you can’t alter their path and calm their nervous system, but I think it’s important to highlight that in our high-stress, busy culture, it’s easy to see how many babies are being born with low vagal tone.

Introducing food to your baby can support vagal stimulation, or irritate the vagus.

If you have a baby who gags on their milk, or swallows a lot of air, it’s likely that part of their issue is from the vagus nerve. It’s important to let these babies explore with spoons and safe toys in their mouth, to trigger the gag reflex, as this is one way the vagus nerve is stimulated and developed.

Some babies with low vagal tone will be so averse to things in their mouth that they may have refused the breast (preferring the ease of a bottle), never put things in their mouths, and maybe even a serious drooler (those ones you have to have bibs on all the time). These babies might gag way too often with food in their mouth and appear to have texture or sensory aversions to food from a young age. While babyled weaning is a great option for most, I would actually recommend puree for these babies, to get them used to different foods and textures in their mouth, before slowly increasing the lumps and changing the consistency.

Babies who appear to react to a lot of different foods (but nothing in particular) may also have low vagal tone. It impacts the stomach contractility, slowing it down, as well as digestive tract contractility. Food tends to sit in the stomach longer (lending itself to reflux or silent reflux), or end up undigested in the lower bowel, either causing constipation or explosive poos.

If your baby has true food sensitivities, or gut microbe imbalances, this can trigger inflammation which the vagus will detect. If the vagus itself becomes inflamed, it’s function may be reduced, lending itself to a downward spiral towards low vagal tone. The best foods for vagus nerve health include a whole foods diet, with lots of vegetables, proteins and healthy fats, as well as small portions of fruit and grains (if you include those in your diet).

Causes of low vagal tone in babies

The biggest cause as mentioned before is chronic stress. This may look different to each individual, as we all respond to stress differently.

Exposures from the environment, food choices, emotional stress, infections; all these things add up to create ‘chronic stress’ in almost every modern mother. To be honest I think it’s completely unavoidable and that is part of the problem. A traumatic birth may also contribute to a period of high stress for mum and baby, reducing the tone of the vagus.

The second cause is from jaw (TMJ) dysfunction. Neurologically, the jaw connects with the vagus nerve, and the two often go hand in hand. I personally assess the jaw in every baby, because of this strong neurological connection.

When you provide a healthy environment for a body, often the vagus nerve begins to work optimally without any help. This is often the case for babies, whereas adults almost always require vagal stimulating exercises to increase their vagal tone. Some babies might need some extra support, but it is my clinical experience that babies have a very pliable nervous system that responds to gentle changes in their environment.

How to stimulate the vagus nerve in your baby

The best way to stimulate the vagus nerve is to establish breastfeeding, and let your baby mouth suitable toys or cutlery. Having a secure emotional attachment to caregivers is also important, as this activates part of the vagus nerve.

If you’re concerned about your baby’s vagal tone, and want their jaw checked out, I am available for in-person consultations.