10 March 2006

Tooth decay and diet

Although the decline in tooth decay in many countries has been largely linked to fluoride exposure and improved dental hygiene, eating habits still affect the risk of tooth decay.

Although the decline in tooth decay in many countries has been largely linked to fluoride exposure and improved dental hygiene, eating habits still affect the risk of tooth decay.

Fermentable carbohydrates
For many years, the simplified message to prevent tooth decay was "don't eat too much sugar and sugary foods". Over the last few decades sugar intake in many countries has remained constant whilst caries levels have declined.

This suggests that where appropriate oral hygiene is practiced (i.e. regular tooth brushing using fluoride toothpaste), the role of sugars in tooth decay is less manifest.

Advice to replace sugar with starchy foods to avoid tooth decay is of questionable value. It is now known that any food containing fermentable carbohydrates can contribute to tooth decay.

This means that as well as sweets and confectionery, pasta, rice, potato crisps, fruits, and even bread can set the scene for demineralisation.

For example, a study testing the acid-producing potential of various starchy foods including pasta, rice and bread, found that these foods produced the same amount of acid as a 10% sucrose (table sugar) solution.

Another study found that acid formation in plaque after eating soft bread or potato chips was greater and lasted longer than after eating sucrose.

Food characteristics
The physical characteristics of a food, particularly how much it clings to the teeth also influence the tooth decay equation.

Foods that adhere to the teeth increase the risk of tooth decay compared to foods that clear from the mouth quickly. For example, crisps and biscuits stick to teeth for longer periods than foods such as caramels and jelly beans.

This may be because caramels and jellybeans contain soluble sugars that are washed away more quickly by saliva. The longer carbohydrate-containing foods are around the teeth, the more time bacteria have to produce acid and the greater the chance of demineralisation.

Frequency of eating
There is some debate over the relative importance of the frequency of consuming carbohydrate foods and its link with dental caries. As with the relationship between diet and caries, the link appears to have been weakened with the adoption of good oral hygiene and fluoride.

Each time we nibble a food or sip a drink containing carbohydrates, any decay-causing bacteria present on the teeth start to produce acid and demineralisation commences.

This continues for 20 to 30 minutes after eating or drinking, longer if food debris is locally entrapped or remains in the mouth. In between periods of eating and drinking saliva works to neutralise the acids and assist in the process of remineralisation.

If food or drink is taken too frequently, the tooth enamel does not have a chance to remineralise completely and caries can start to occur. This is why nibbling or sipping continuously throughout the day should be discouraged.

The best advice is to limit the consumption of food and drink containing carbohydrates to no more than six occasions per day and ensure teeth are brushed with fluoride toothpaste twice a day.

Baby bottle caries or nursing caries is a condition in which infants’ teeth are damaged by prolonged frequent exposure to drinks containing sugars – usually via a baby feeding bottle.

In particular, problems arise when infants are put to sleep with a bottle of formula or juice. The flow of saliva is greatly reduced during sleep and the sweet liquid pools around the teeth for extended periods of time. This provides the perfect environment for tooth decay to develop.

Protective foods
Some foods help protect against tooth decay. For example, hard cheese increases the flow of saliva. Cheese also contains calcium, phosphate and casein, a milk protein, which protects against demineralisation.

Finishing a meal with a piece of cheese helps counteract acids produced from carbohydrate foods eaten at the same meal. Milk also contains calcium, phosphate and casein, and the milk sugar, lactose, is less cariogenic (caries causing) than other sugars.

Nevertheless, caries have been found in children breastfed frequently on demand.

Source: The European Food Information Council (


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