Diet, Sugar and Cavities: What the Evidence Actually Shows

It is not how much sugar you eat. It is how often, in what form, and what comes with it. Here is what the cariology evidence actually says.

Two patients with identical-looking diets came through my chair in the same week. Both drank a 330 ml can of cola each day. One had no new cavities in five years. The other had four interproximal lesions on the lower posterior teeth. The difference was not the sugar volume. It was when, and how, they drank it. The first patient drank her cola with lunch, finished in ten minutes, then brushed two hours later. The second sipped the same can across three hours at his desk, all afternoon. Same sugar load. Completely different acid exposure. How cavities actually form Cavities — dental caries — are not caused by sugar directly. They are caused by acid produced when oral bacteria, principally Streptococcus mutans and Lactobacillus species, ferment fermentable carbohydrates. Below a critical pH of around 5.5, the enamel begins to lose mineral. Above that pH, saliva works to remineralise it. A tooth is in constant flux between demineralisation and remineralisation, every day, all day. The Vipeholm studies in 1950s Sweden — still cited in cariology textbooks — showed conclusively that the frequency of sugar intake mattered more than the total quantity. The Cochrane review on dietary sugars and caries, published in 2020, reached the same conclusion. Each separate sugar exposure triggers a pH drop that takes 20 to 40 minutes to recover. What that means for what you eat Five separate sugar exposures across a day will damage teeth more than one larger sugar exposure at a single sitting. So: Dessert after a meal is less harmful than the same dessert grazed across an afternoon Sugar in coffee sipped over an hour is worse than the same sugar in coffee drunk in ten minutes Children who graze on biscuits between meals have a higher caries risk than children who eat the same biscuits as a single after-school snack Sticky sugars — toffees, dried fruit, dates pressed in date pastes — hold sugar against the tooth far longer than liquid sugars that wash away The hidden-sugar problem The patients I see with the most surprising new cavities are usually not the ones eating sweets. They are eating things they did not realise were sugary. Common hidden-sugar items in Sharjah patient diets: Flavoured yoghurts marketed as healthy — often 12 to 18 g of sugar per pot Fruit juices, including freshly squeezed, which deliver a concentrated acid and sugar dose Karak chai with two or three spo…

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