Dental decay

Which foods and drinks damage your teeth? And what can you do to prevent decay?

Want the awful tooth?

Until 1996, the health of kids' teeth in Australia was improving, but since then a rise in tooth decay has turned that around. In collaboration with the Australian Dental Association (Victorian Branch), we tested 50 foods and 35 drinks, all popular brands and products readily available in most supermarkets, to see which were the most damaging to dental health.

On average, six-year-old children now have two decayed or filled baby teeth, while 15-year-olds have two decayed, missing or filled permanent teeth.

Experts particularly blame our increasing consumption of sugary snacks and drinks, including fruit juices; on average, Australians drink about 113L of soft drink per year, an increase of 240% over 30 years. But there are many other foods and drinks that are potentially harmful for teeth.

The worst offenders

We compared the sugar content and acidity of 85 processed foods and drinks and categorised them as high, moderate or low risk. See the test results here.

  • High-risk products contained a lot of sugar and had high acidity. Foods included some muesli bars and processed fruit snacks, and drinks included soft drinks, fruit cordials and fruit drinks. Unfortunately, many of these foods are promoted as "healthy" snacks for kids' lunch boxes.
  • Moderate-risk products that we tested either contained a lot of sugar or had high acidity, but not both.
  • Low-risk products contained less sugar and were not highly acidic.


All the confectionery products we tested are in the high-risk category. Two brands, Wonka Fruit Tingles and Warheads Juniors Extreme Sour Hard Candy, stand out as the worst.

They contain more than 80% sugar and they're more acidic (with pH values of 2.35 and 2.06 respectively) than any other food or drink on test. They also have high acid reserves, making it harder for saliva to neutralise the acid, so the teeth are exposed for longer.

Of greater concern is the fact that some of the muesli bars we tested fall into the high-risk category, as well as other products promoted for kids' lunch boxes such as processed fruit snacks. These foods are often sticky, which increases the time the teeth are exposed to sugar and acid.

Uncle Toby's Fruit Fix and Robern FruBears also have high acid reserves, which ups the risk even further.


Some fruits can be acidic enough to cause dental erosion. Lemons and other citrus are obvious examples, but white grapes and Red Delicious apples are also fairly acidic (pH 4.03 and 4.37 respectively).

Less acidic fruits include bananas and melons. Although fruit can be sweet, most of the sugar is fructose. The bacteria in our mouths finds fructose harder to deal with than ordinary sugar (sucrose), so fruits are generally less harmful to teeth than processed foods with similar sugar content.


Fizzy drinks feature prominently in the high-risk category. Market leader Coca-Cola packs 10 teaspoons of sugar into a 375mL can. Coke is also very acidic (pH 2.53) as it contains phosphoric acid. Pepsi contains even more sugar and is even more acidic (pH 2.45).Sugar-free alternatives such as Coke Zero and Pepsi Max can also damage teeth. 

Caffeine-loaded V energy drink stands out as having a higher acid reserve than most other soft drinks. Fruit cordials such as Golden Circle Pineapple Crush and fruit drinks such as Pop Tops Apple Blackcurrant Drink are also in the high-risk category.

Fruit juices, although often seen as healthy, can cause dental erosion due to their acidity, as well as other health issues because of their high sugar content – even though it's natural sugar. Studies show that fruit juices are the most resistant to saliva's buffering effect, followed by fruit-based carbonated drinks.

The Australian Beverages Council argues that drinks leave the mouth quickly and are less likely to cause tooth decay than foods that stick to the teeth. However, they can still cause erosion. A study of children in the UK found dental erosion was associated with consumption of fizzy drinks (and to a lesser extent, fruit juices).

How tooth decay and erosion occur

Scientific studies consistently point to sugars as the most important dietary factor in causing tooth decay. Less well known is the fact that acidic foods and drinks, even sugar-free ones, can also damage teeth. Acid can directly damage the enamel surface of teeth – a process known as dental erosion.

A recent survey found 68% of Australian children aged between six and 15 had at least one tooth that showed signs of erosion. Teeth are made up of thousands of tiny crystals of calcium phosphate that are in a constant state of flux, as calcium and phosphate ions move back and forth between the tooth enamel and saliva.

Under acidic conditions (pH less than about 5.5), there is a net loss of calcium and phosphate ions from the tooth, a process known as demineralisation.

Tooth decay

Tooth decay is caused by bacteria in plaque, which forms as a layer on the surfaces of teeth. These bacteria use sugar for energy, and produce acids as a by-product that can damage the crystals of the teeth. The more often you have sugary foods or drinks, the more acid the bacteria make and the more damage occurs.

If you only eat three meals a day, with no sugary snacks or drinks in between, the bacteria only have three opportunities to produce acid so there is minimal damage to your teeth. However, sugary drinks and snacks extend the time the bacteria are producing acid, increasing your risk of tooth decay.

As damage accumulates, the tooth can become weak and break down, leading to a hole or cavity that may require a dental filling. If this process continues it can cause complete breakdown of the tooth, and the only treatment option is to have it pulled.

Dental erosion

Dental erosion is caused by acids that come directly from foods or drinks (or from stomach acids if you've recently eaten something that doesn't agree with you). This acid attack is stronger than that produced by the bacteria in the tooth decay process, and leads to the complete dissolution of the outer crystals of the tooth.

Every time an acidic food or drink passes your teeth and drops the pH in the mouth to below 5.5, there's a chance the outer crystals are dissolving and reducing the amount of tooth you have left.

Fortunately, your teeth are constantly bathed in saliva, which contains protective components such as calcium and phosphate that can help repair some of the damage. Saliva can also wash sugar and acid into the stomach and neutralise some of the acids.

However, if sugary or acidic foods are eaten too often and too regularly, the damage they cause can't be balanced by the saliva, and damage to the teeth will only get worse.

Additionally, saliva can't always neutralise the effects of foods or drinks that are very acidic or have high acid reserves.

Seven ways to prevent tooth decay and erosion

If you have a sensible diet and a good dental hygiene routine, you're less likely to suffer decay or erosion. Follow these tips to keep a healthy smile on your dial

  • Brush twice a day and floss once a day. But don't brush your teeth immediately after acidic foods or drinks, as you can wear away the softened enamel before saliva has had a chance to re-harden it.
  • Limit sugary foods and drinks, as these allow bacteria in the plaque to produce the acids that dissolve teeth. Particularly avoid sticky snacks – such as sweet muesli bars – that hold the sugar in your mouth for longer.
  • Limit highly acidic foods and drinks. Using a straw can reduce the contact of an acidic drink with your teeth.
  • Restrict high-risk foods and drinks to a once-a-week treat. They'll do less damage if you have them at mealtimes and if you rinse your mouth straight after, or have a protective food such as an unsweetened dairy product or sugar-free chewing gum.
  • Use fluoride toothpaste as exposure to fluoride can help control the development of decay.
  • Drink fluoridated water instead of sugary or acidic soft drinks.
  • Have regular dental check-ups.

This article was co-authored by Nathan Cochrane of the Cooperative Research Centre (CRC) for Oral Health Science.