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Does Breastmilk, Breastfeeding, Or Formula Cause Cavities?

March 21, 2023

First of all, spoiler: no. As I wrote about last article, it’s about diet frequency more than anything else. Almost everything we eat has some cavity-causing potential, so we want to be smart about when we eat those things. 

Infants under 1-year-old need to consume breastmilk or infant formula about every 3 hours (plus or minus, age depending) throughout day and night. Two things happen that make cavities possible, the first being the child becomes infected with the bacteria that cause cavities, usually from a primary caregiver, sibling, or playmate. The second being that as we introduce solid foods into the diet, the dental pellicle (the layer on your teeth that gets removed with cleanings, leaving your teeth feeling super slick) which is formed of different salivary proteins, changes and better enables bacteria to form a biofilm (which, when it accumulates visibly, we call “plaque” or “tooth poop”). So, there’s bacteria now and they want to stick to the teeth, too! The 1 year mark is usually when your pediatrician informs you that developmentally speaking, your child no longer needs to eat around the clock, and can, developmentally speaking, sleep through the night without needing to feed. 

The problem is, from the baby’s perspective, they’ve always been fed throughout the night. When adults wake up at night, we usually toss a bit and go back to sleep. For babies, it can be unsettling to be in a dark room alone, and whenever this has happened in the past, baby calls mom/dad in, and she/he gives baby warm snuggles, a belly full of milk/formula, and baby drifts back into blissful sleep. It’s HARD to change this pattern of behavior. This is when pediatricians talk about sleep training, i.e. teaching your child what the new behaviors are going to be. And every kiddo is different.

As previously said, the diet side of the cavity battle has nothing to do with what’s in the stomach itself, whether breastmilk or formula, but instead what’s on the teeth, how long it’s on the teeth for, and how frequently it’s re-applied to the teeth. When we sleep, we don’t make much saliva. Even if you sleep with your mouth closed, breathing through your nose (as is ideal), you still wake up with a dry mouth/morning breath. Whatever was on your teeth at night, is going to have STAYED on your teeth all night. This is why we want toothbrushing to be the last thing we do and toothpaste to be the last thing on our teeth at night (the little residual amounts of fluoride still there get to soak in all night long like lotion on your skin). If residual milk/formula sugars are there all night long, then THAT is available to the sugar bugs to feast on, especially if we recharge them with a fresh mouthful every 2-3 hours throughout the night. This is the reason that what we now call Early Childhood Caries used to be called Baby Bottle Caries.

What your dentist wants for you is not to discontinue breast/formula feeding, or even necessarily to cut out milk from the bedtime routine. What we want is for milk/formula to not be the last thing on your child’s teeth while they sleep. Have a routine where the teeth are brushed after eating or, at a minimum, wiping the teeth with a water-damp wash cloth during the nightfeeds while you are transitioning with sleep training per your pediatrician’s guidance. The end game is for kids to toss/turn and go back to sleep, and for mom and dad to toss/turn and go back to sleep, and for EVERYONE to have an undisturbed, full night’s sleep. That’s the goal we all can agree is desirable. How to get there is different for everyone. 

Breastfeeding is super healthy for a child, and it is never the goal of your dentist to tell you to stop or when to stop. For my kids, my wife and I had to do a combination of breastfeeding and formula feeding, and different approaches to sleep training worked for our two kids. The goal with everything diet-wise for our teeth is frequency. We want kids to be well-fed, however that may be, but for the sugar bugs to NOT be well-fed. For your child, we need full bellies. For the sugar bugs, we need to have times when our teeth get a break from non-water food/drink exposure to recover/remineralize. This means learning new behaviors to adapt to new needs (or disappearance of the need to eat every 2-3 hours) and developing patterns of behavior and rules in the household that do not involve snacking and sipping throughout the day or night and in between meals. We want healthy teeth and a full night’s sleep for everyone involved. Breastfeeding, breastmilk, and formula do not need to cause any cavities, but the habits that surround them can influence this one way or the other.  

Example of Early Childhood Caries due frequent feeding without brushing/wiping after. You’ll notice the cavities are all on the top front teeth, where the milk hits. The tongue tends to protect the lower front teeth from exposure.

A kid playing with his toys

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