Calcium for strong bones and teeth... What does this mean?

Date: 25 April 2025

Introduction

Do you ever wonder about the truth of expressions like "milk is for strong bones and teeth"? Well I am going to dive into the science behind this common expression.

Before we talk about the role of milk in our diet, first you should understand that carbohydrates, proteins, fats, vitamins, minerals and water are the six essential nutrients for human health that are obtained through the diet. While carbs and fats are the main sources of energy, proteins aid in the muscle recovery/development and vitamins and minerals aid in cell signalling. However, an excess of any one of these components is detrimental to human health.

Context and why this article is important to me

As a child, I developed a pretty unhealthy addiction to junk food, which lead to a low self-control as an adult. I was addicted to lollies and sweets. I faced and am still facing a never-ending battle with dental health. As I reflect on my self destructive behaviour, I realise this is not something I want to pass on to my future kids. Therefore, I think it is important to understand the structure of the teeth and how dental cavities arise/how they can be prevented.

The chemistry of teeth and bones

The teeth (and bones) are made up of a mineral called hydroxyapatite. Hydroxyapatite is a calcium mineral made up primarily of phosphates and hydroxides with 4-6% carbonates. The common chemical formula used to describe it is Ca₅(PO₄)3OH.1

Hydroxyapatite is insoluble in water at physiological pH (pH=6-8), which is the reason teeth and bones do not dissolve. Yet, hydroxyapatite in the teeth and bones differs from that found in nature. The coolest thing happens in the body, whereby collagen self-assembles to form a scafold by an unknown mechanism that is highly organised and arranges the calcium phosphate in such a way to make them very strong and resistant to decay. The collagen acts as an additional protective sheath.2

Hydroxyapatite as an indicator for age

Like many other minerals, hydroxyapatite is prone to substitution. Trace amounts of Strontium can substitute for calcium. As Sr is commonly found in plants, rocks and in the water supply at distinct concentrations in different areas, the concentration of Sr can be correlated with different regions to show where a person travelled. Also, due to radioactive decay, the ratios of different Sr atoms can be used to track the time of movement.3

But that’s not really important in understanding how apatite affects tooth health now… I guess the most important thing is that the crystallinity of the hydroxyapatite in bones and teeth decreases with age owing to the increased substitution of CO₃^2- for OH and phosphates.4

Hydroxyapatite decay

Consider yourself very lucky if you have never experienced a filling; as tooth decay is very common, even at a young age - I should know! Tooth decay occurs when hydroxyapatite reacts with acids at pH=<5.5. In this reaction, carbonate (CO₃^2-) will substitute for either hydroxide (type A) or phosphate (type B), increasing the solubility of hydroxyapatite (especially in acidic environments) and subsequently producing dental caries.5 Acids are the culprit for such substitution.

Sugars themselves are not acidic. It is actually a strain of acid-producing bacteria, Streptococcus mutans, that build up on the tooth and facilitate the fermentation of sugars/carbohydrates to create an acidic environment.6 Thus, anything containing sugars, carbohydrates (including athlete gels) or citric acids/lactic acids will ultimately create this environment. Organic acids (citric acid, lactic acid, oleic acid, tartaric acid etc.) are often found in many preserved foods, in fruits (higher concentrations in dried fruits) and beverages. In addition, the carbonated drinks including soda water and colas also contribute to an acidic environment in the mouth.

While some carbohydrate/sugar intake is okay (it has to be as it provides most of our energy), it is the excess intake that causes dental decay. But what is excess? It differs between people so how do I know when it is too much? Well you can’t really know. However, remedies can counteract the effects of sugar on our teeth.

Remedies for tooth decay

As tooth decay is one of the leading causes of injury/illness worldwide, there has been a lot of research conducted in this area.

Some simple remedies include:

1. Limit snacking and junk food intake

The first and obvious way to prevent tooth decay is to cut down the sugars in the diet. This means limiting the number of fruits and sweet foods consumed. In addition to sweets, limiting the amount of snacking will also prevent a build up of acidity in the mouth and allow your saliva to neutralise acids.

2. Switch to a fluoride based toothpaste

You may have heard of special toothpastes like neutrafluor - that is a behind the counter medicine. What is special about this toothpaste is the fluorine content. Fluoride is often used to remediate the detrimental effects of sugars on tooth decay. It works because fluoride will substitute for any carbonate or hydroxide to produce a (hydroxy)fluoroapatite. Fluoroapatite is less soluble than hydroxyapatite.7.

But even after I started using this toothpaste, my dentist still observed tooth decay. He then instructed me not to rinse my mouth after brushing - that way the fluoride would remain on my teeth during sleep. This worked and I have avoided fillings for a while now.

3. Dairy consumption

Do you ever hear about the protective effects of milk on teeth? Some of the negative effects caused by sugars can be counteracted by chewing on cheese or drinking milk. Why is that? Funnily enough, milk consists of a high concentration of calcium and phosphates. They are solubilised due to the presence of proteins called caseins. These caseins solubilise calcium and phosphate through micelles (think of soaps). The lactate also aids in solubilising the calcium by chelation (the lactate forms a soluble complex with Ca).

But it’s not just that. The presence of buffering calcium, phosphate and lactate create an environment that can resist changes in pH. The peptides (such as Whey) present also prevent adhesion of bacteria that cause tooth decay and play a role in immune protection.8

Impact of lactose on teeth

As I wrote this article, I was questioning “what about lactose?”. Afterall lactose is a carbohydrate, a dissacharide that consists of a glucose and galactose unit connected through a ß-glycidic bond (this a term to describe how the carbohydrate molecules sit in space).

Milk contains 4-5% lactate which can be digested by enzymes in the mouth. However, the breakdown of lactose is a lot slower than typical table sugar (sucrose: made up of glucose and fructose connected by an alpha-glycidic bond). Lactose therefore is not hydrolysed in the mouth, but rather in the small intestines by the enzyme lactase (lactase-pylorizin hydrolase). In addition, the pH of lactose is ~6 compared to <5 for sucrose.9

A number of reserachers have isolated different components of milk to ascertain what component contributes to the protective effects.10 The general consensus is that it is not one part, but the food matrix itself that plays an important role in the maintenance of tooth and bone health.

What about coffee?

Now, I love coffee… So I wondered what was the impact of heated milk or the milk/coffee mixture on dental health. I found that heating milk denatures the whey proteins and facilitates the breakdown of lactose to its individual monosacharides. This is detrimental to tooth health; however, as previously stated, it is not one component that provides the protective effect on tooth, but rather a make up of different proteins within the food matrix. Thus, it may not be a big problem.

I found that roasted coffee contains a high level of antioxidants that reduce the adhesion of S. Mutans. Similar findings have been reported for teas including black tea and green tea.11

Benefits of dairy on gut health

Did you know that the texture and structure of foods plays a large role in how the nutrients present are taken up? As I mentioned previously, milk aids in the solubility of otherwise insoluble calcium and phosphate. These ions are available for adsorption by the body. In contrast to this, the conversion of milk into cheese results in a slower amino acid adsorption owing to the food matrix and need to breakdown the coagulated proteins. This in turn results in a slower rate of gastric emptying and thus digestion.

Gastric emptying is a term used to describe the process whereby food leaves the stomach and moves into the small intestine for adsorption of macronutrients. Acidic environments as well as food matrices tend to slow down gastric emptying. Delayed gastric emptying can cause reflux events. So ideally, a quicker emptying is better for nutrient adsorption.

So milk and yogurt - solely based on their composition and pH can improve the rate of gastric emptying as well as nutrient adsorption. In fact, if you have a glass of milk first thing in the morning, the pH of the stomach will be high (>6). Due to the buffering capacity of milk, there is a resistance to decreasing the pH which ultimately assists in the rate of gastric emptying and rapid amino acid adsorption.

This does not mean that cheese is bad though. Cheese is an excellent source of dairy and possesses a range of probiotics that are beneficial for the gut. Other fermented foods including yogurts, probiotic drinks and kefir may also provide immune benefits as well as assist in HDL and LDL-cholesterol clearing rates.12

Calcium and heart health

While the intake of foods high in calcium are important, vitamins also play a role in calcium homeostasis, including how the body adsorbs and uses calcium. For instance, vitamin D affects the solubility of calcium in our blood, where higher vitamin D concentrations results in a decrease in Ca²⁺ soluble ions in the blood.13

With increasing calcium in the blood, there is a chance of coronary artery calcification whereby calcium builds up in the walls of the arteries, resulting in hardening and narrowing of the arterial walls. While there is a lot of contradictory studies in literature, calcification is thought to be induced by the presence of LDL-cholesterol. High levels of the LDL-cholesterol leads to a buildup and crystallisation of fatty-acid, cholesterol salts on the arterial wall.14 Once the cholesterol crystallises, it is recognised as a foreign body and induces an immune response which can result in thrombosis or myocardial infarction.15

This process is called “calcification”. It should be noted that calcification is a normal process that occurs throughout life and is common in healthy people. One could say that the degree of calification in the artieries is a determinant on one’s age.16 Like many bodily processes, calcification can be slowed. In fact, Vitamin K Binds to a Matrix GLA protein that reverses/prevents calcification by preventing calcium and phosphorus circulation, as well as removing them from the vessel walls.17

Take home messages

• We are what we eat. Literally!
• Nature is very cool at using our environment to make up our bodies.
• Milk is good for the teeth and for health in general.
• Everything we eat should be in moderation.