Many factors influence caries development, including the presence of plaque-producing bacteria, innate susceptibility of tooth surfaces, frequency of eating, snacking behaviour, oral hygiene practices, fluoride availability, and salivary flow and composition. All carbohydrates, including starchy foods, especially highly processed starches in savoury snacks, and foods containing sugars such as cakes, biscuits, jam, honey, fruits and fruit juices can be used by bacteria to produce acids, which accelerate demineralisation of tooth enamel. Saliva contains protective minerals (calcium and phosphates) that buffer the bacterial acids and promote remineralisation. The greater the salivary flow, the more rapid the remineralisation. It is the balance between acid production and salivary recovery that determines susceptibility to caries.

Repeated acid attacks which do not give teeth the time to recover increase risk of caries, so small amounts of sugar and other fermentable carbohydrates eaten frequently during the day will increase caries risk more than large amounts eaten infrequently. Additionally, the amount of sugar consumed is less important than how quickly it is cleared from the mouth. Sticky foods like breads or raisins stay in the mouth much longer, and increase the potential for decay. Calcium-rich foods like cheese, eaten immediately after sugar, can help protect against demineralisation.

The relationship between the amount of sugar consumed and the levels of decay in individuals is actually very weak. The frequency of consumption is a better, but still poor, predictor. Dietary methods of preventing caries have not been shown to be effective. The most effective means of preventing caries is routine use of fluoride toothpaste in conjunction with proper oral hygiene practices.

In a report by the UK COMA Committee in 1989, sugars were classified as being extrinsic or intrinsic. A similar definition was proposed in a WHO Report (916). Extrinsic sugars were defined as those added to a food and intrinsic sugars as those “naturally integrated into the cellular structure”, eg those in fruits and vegetables. The report added that the physical location of sugars influenced their availability for bacterial metabolism and therefore their influences on caries. However, research has shown that extrinsic and intrinsic sugars impact plaque acidity equally. And the rate of metabolism of sugars in whole fruits to acids by plaque bacteria is identical to that of fruit juices.

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