Is milk good or bad for my toddler's teeth?

Milk toddler’s teeth

Be it breast milk, formula or cow's milk, drinking milk forms an important part of a diet during the early childhood years.  Among other benefits, milk is packed full of calcium and has fat to provide energy and growth.  Yet we also hear that milk can be a contributor to decay in children's teeth.  So is milk really good or bad for toddler's teeth?  And when do we have to be careful?

Thankfully these days, I don't see much decay in toddlers aged 1-3 years.  I'm aware that other dentists do and that things certainly can go wrong, but for a variety of reasons it just doesn't walk in through my door too often.  Having said that, when we do see decay (caries) in this age group, it can be quite dramatic.  At times, decay can affect most or all of the teeth present in the mouth, can progress rapidly and simply be a nightmare to deal with.  Terms such as 'nursing caries', 'bottle caries' and 'early childhood caries' may be used to describe these presentations.  And the cause when we see problems like this can, somewhat strangely, often be milk! 

I recently spent some time with my son's 4-year-old kinder class and we ran through some really simple activities relating to dental health.  One of these involved placing some cardboard cut-outs of food items into categories of 'GOOD' foods and 'SOMETIMES' foods.  The kids were actually really good at this, with most being able to identify that vegetables belong in the 'GOOD' category, donuts in the 'SOMETIMES' category and so on.  However, when we got to the cardboard milk container, there was less accord.  Most of the class pointed towards the 'GOOD' section but there was one vocal boy in particular who was adamant that milk was bad for our teeth and shouldn't be placed there.  This quickly degenerated into a shouting match which I found myself poorly equipped to adjudicate!  Things in life are obviously not always black or white, good or bad, health or unhealthy.  Often we need to break down the science of matters in order to explain why some things may be good in certain circumstances and not so good in others.  Although milk should generally rest firmly in the 'GOOD' category, there are certain select circumstances where we do need to be careful.

What is good with milk?

Most of us are well aware that decay (or caries) on teeth is caused by bacteria in plaque, combined with sugar.  Most of the time the sugar that we are talking about is sucrose or simply glucose.  Certain bacteria in the mouth are good at metabolizing glucose and form acid as a by-product.  If left for a long enough period of time, it is this acid that can form dental decay.  It is the frequency of sugar intake that is more likely to cause significant problems rather than the dose of sugar at any one point in time.

Drinking milk would clearly seem unlikely to cause this.  Milk is loaded with calcium which can guard against tooth decay.  It is high in pH (not acidic) and can act as a pretty effective buffer.  And the 'sugar' is milk is not glucose but lactose, which is only very poorly converted to acid by bacteria.  So in the normal course of events, milk is not only unlikely to cause dental decay but may actually be somewhat protective against it!  This may be the origin of 'milk and cookies' as a famous snack combination, where a sugary treat is somewhat offset by the accompaniment of a drink to quickly restore pH and calcium balance in the mouth.

When can milk go bad?

This can be a bit complex and I certainly didn't venture an explanation at 4-year old kinder.  But basically, milk can be a problem in very low concentrations over very long periods of time.  This is unlikely to ever be relevant in adult life but can be an issue in the early childhood years.  When small amounts of milk are left to bathe the mouth and teeth over a long period of time, bacteria in the mouth can adapt.  Bacteria which might normally metabolize lactose in milk only poorly can adapt and start to use lactose efficiently to produce acid as would more commonly be the case with other sugars (sucrose or glucose).  Over time, having these 'adapted' bacteria and a continued constant source of lactose from milk can be a recipe for disaster.

The main scenario where we see the above happen has traditionally been with 'bottle propping' - a practice whereby an infant or toddler would be sent to bed with a bottle full of milk which is left to slowly drip or be sucked in to the mouth during the course of the night.  The lactose in milk combined with the long exposure time and the low saliva flow during sleep can combine to cause significant problems. 

The advice

Milk is generally a great drink and a great snack for the teeth and health in general.  Rare situations where milk may contact the teeth over a very prolonged period should be avoided.  Overall, toddlers should ideally not have residue of food or drink consistently around their teeth for long periods of time during sleep.  The simplest advice is to make sure that teeth are surrounded by saliva, water or even toothpaste residue when kids are asleep.  Making sure our kid's teeth are cleaned just before bed and this is not followed by any food or drink might sound simple but is one of the most important pieces of advice you will ever hear from your dentist.


Read more about children's dentistry at our practice or feel free to contact us to discuss advice which may be appropriate for you.


Dr. Aaron Martin is a registered dentist and principal dentist at Dentists of Alphington.  The contents of this blog represent the thoughts and opinions of the author and should not be considered as a substitute for professional advice in any way.  Any information provided is broad in nature and may not apply to an individual's circumstances.  Individuals should seek their own advice from a health professional prior to any treatments or decisions.