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  • Heather Wallace


How the Digestive System Affects Your Baby’s Circadian Rhythm, and How the Night Feeds Affect Your Baby’s Digestive System

This post might be a bit confusing. But there’s some interesting research out there that I wanted to share. First off, I completely understand and support the fact that every parent has their own philosophy on how they respond to their baby’s call for support in the nighttime hours. This blog post might not resonate with you, because your value for allowing your baby to take the lead on night weaning is stronger than the value of teaching your baby a new way to fall asleep and stay asleep. And this is 100% OKAY!!! My goal in this post is to focus on one function of the body that I find fascinating, which is how the digestive system guides the circadian rhythm.

What controls your baby’s digestive system?
This is the interesting part… your baby’s Parasympathetic Nervous System (“PNS” is what I will call it) controls your baby’s digestive system. Part of the PNS’s job is to “relax or reduce your body’s activities.” (1) This includes relaxing your baby’s muscles for digestion. The term “rest and digest” is often associated with the PNS. The PNS actually is developed and matured at the end of the second trimester in utero (2), alongside the Sympathetic Nervous System (“SNS”), which is your baby’s “fight-or-flight” mode. Because the PNS helps your baby’s muscles relax enough to start the digestion process, it is often called the “rest-and-digest” state. (5)

What is the role of the digestive system on the circadian rhythm?
Your baby’s circadian rhythm is “driven by a master clock in the brain and informed by external factors like light and food.” (3)(4) Not only are hormones secreted from the brain to the body in order to drive circadian rhythm, but hormones originating from the gut send signals as well to add to the development and maintenance of the circadian rhythm.

An appropriately developed circadian rhythm also allows the PNS to take over at the right time. When a baby’s PNS is working properly and not disrupted by multiple wakings in the night, your baby’s body has the ability to work on getting into a restful state and digesting food (milk) properly.

How a feeding at night affects the PNS and digestive system
When your child was a newborn it was normal for her to wake often in the night. We typically responded to these wakings with a feeding. And often with every waking and feed came a bowel movement (or a blowout if you’re unfortunate!!). As her stomach capacity grew, the circadian rhythm developed in order to teach her body when it was daytime and when it was nighttime, and self-soothing skills emerged, these wakings became less and less. However, some babies are quite habitual and the routine of waking at a certain point in the night and the waking being reinforced with milk can override a baby’s natural progression towards a healthy developing circadian rhythm and digestion system.

Your baby needs a consolidated night in order to rest-and-digest. A continuous night’s sleep allows your baby’s digestive system to expel toxins and metabolize nutrients. If your baby is waking often in the night for a feed, not only does her digestive system not have a chance to get into a restful, relaxed state in order to perform these important bodily functions, but it can also cause your baby’s circadian rhythm (which tells your baby’s body when to sleep and when to be awake) to become out of sync, thus your baby’s digestive system becoming out of sync. When your baby’s digestive system is out of sync it often causes a poop at just the wrong time! (4 am for example!) When a feeding (or more) happens during the night for a prolonged time your baby may not get the benefits of absorbing nutrients from their milk due to a negatively affected digestive system or the lack of the PNS taking over at night to cause rest to your digestive system. Your baby’s bowels might be disorganized which causes an imbalance to the circadian rhythm.

Benefits of night-weaning on your baby’s body systems
If your baby is over 4-6 months old (10), weighs at least 12-15 lb.(9) and is still waking up at night for one (or more) feedings, she could benefit from taking steps towards night-weaning. This decision is solely yours to make, but often pediatricians encourage parents to make this transition to a consolidated 11-12 hour night without feedings/disruptions around this age. Removing feedings at night not only helps establish a more appropriate circadian rhythm and efficient digestion, but can decrease your baby’s fight-or-flight response which decreases cortisol levels. If you think about it, when a baby does not have self-soothing skills and relies on the parent to help her get back to sleep, either with feeding, rocking or something else external, the baby wakes almost in a fight response. You can see from the sharp shrills of the cries, clenched fists, and kicking legs. This fight/stress response is temporarily appeased by getting help back to sleep, but may happen just a few hours later. And night after night well into the first year it is happening. When your baby’s sympathetic nervous system (“SNS”, triggered by the fight-or-flight response) takes over at night, the PNS is not allowed to do its job of resting and digesting. When a baby abstains from feeding in the night hours it promotes healthy digestion where the body has time to slowly digest the milk from her day, which is what you want to encourage. When your baby is able to handle the transition from wakefulness to sleep throughout the night, (yes, even sleep trained babies wake often in the night!) it keeps the baby in a more restful state and lowers stress responses.

The tough decision to remove night feeds
YES, getting to this place of peaceful sleep often requires several days of a triggered sympathetic nervous system as your baby is learning how to fall asleep on her own and transition sleep cycles without support. However, research shows that a temporary increase in the stress response has no effect long-term on an infant’s development or caregiver attachment. The secure attachment and loving relationship established between the parent/caregiver and the infant creates a buffer between this stressful event and the brain, and allows the neural pathways to be properly wired again after a stressful event such as sleep training. (8)

If you have been contemplating moving away from feeding your baby in the night, you can be confident that shifting these nutrients from the night to the daytime hours will have a positive effect on not only your baby’s level of restfulness, but also your baby’s ability to digest properly. If you need support making this big change, I’m here for you! My infant or toddler package provides the one-on-one education and support you need to make the change for the better. If you have a newborn and want to start your newborn’s sleep and feeding journey off on the right foot, my newborn plan provides a gentle and effective step-by-step approach to creating a healthy sleeper. And if you want to tackle sleep training on your own, my blog posts may just encourage you and give you the tips you need to take the leap to sleep train.




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