How sugar affects your dental health

The scale of it

Cutting down on sugar has long-established benefits for general health — excessive consumption is linked to heart disease, obesity, diabetes, and bone problems such as osteoporosis.

It also has a substantial effect on oral health. The higher your sugar intake, the higher your chance of developing oral disease.

And the numbers line up:

• Almost half of all Australian adults exceed the World Health Organization's recommendation for sugar intake
• More than 1 in 3 Australian adults have undetected tooth decay — making it the most prevalent form of oral disease

The word undetected is the important one. These are people who do not know they have it.

What the WHO recommendation actually says

Worth knowing precisely, because it is routinely misquoted.

The WHO guidance concerns free sugars — sugars added to food and drink by the manufacturer, cook or consumer, plus those naturally present in honey, syrups and fruit juice. It does not include the sugars intrinsic to whole fruit, vegetables and milk.

The recommendation is that free sugars stay below 10 per cent of total energy intake, with a further conditional recommendation of below 5 per cent for additional benefit. For an average adult, 5 per cent is roughly six teaspoons a day.

For scale: a single 375 ml can of regular soft drink typically contains around nine to ten teaspoons of sugar — one can exceeds the conditional target for the whole day.

The WHO cites dental caries specifically as a reason for the guidance, not only weight and metabolic health. Decay is one of the conditions the threshold was set to reduce.

The mechanism — and a common misconception

Sugar, in any form, does not damage your teeth directly.

What happens is a process: the natural bacteria in your mouth digest dietary sugars and produce an acidic by-product on your teeth.

Without brushing twice a day with a fluoride toothpaste, that acid dissolves the protective enamel layer, resulting in dental caries.

So there are two levers, not one: how much sugar reaches the bacteria, and how well the acid is managed afterwards.

The acid attack, in detail

The process has a shape, and knowing it explains almost every piece of practical advice on this page.

1. Sugar arrives. Within a minute or two, bacteria in dental plaque begin metabolising it — measurable softening starts within seconds of a soft drink.
2. pH falls. Within about five minutes the plaque pH drops below the critical threshold of around 5.5, at which enamel begins to dissolve. Exposed root surface dissolves at a higher pH — around 6.2 — so receded gums make this happen sooner and more easily.
3. Minerals leave the tooth. Calcium and phosphate are drawn out of the enamel surface. This is demineralisation.
4. Saliva recovers the situation. It buffers the acid, washes the sugar away, and — because it is supersaturated with calcium and phosphate — puts minerals back. This is remineralisation, and fluoride makes the repaired surface more acid-resistant than the original.
5. pH returns to normal, typically after 20 to 40 minutes.

Decay is what happens when step 3 outpaces step 4, repeatedly, over months. A single acid attack does nothing lasting. Five a day, every day, for a year, does.

Why frequency beats quantity

This is the single most useful consequence, and it is counter-intuitive.

Eating a whole chocolate bar in one sitting is one acid attack. Eating one square every hour through the working day is eight — the same sugar, eight times the damage, because the mouth never gets back above the critical pH long enough to repair.

The worst patterns are therefore not the ones people expect:

• Sipping a sweetened drink slowly over an hour is worse than drinking it in five minutes — the trap that catches athletes with sports drinks.
• Grazing on snacks at a desk is worse than the same food eaten with a meal.
• A sweet drink or a bottle at bedtime is the worst of all, because saliva flow falls overnight and the acid sits undisturbed for hours.
• Sticky and slow-dissolving sweets — dried fruit, toffee, boiled lollies — extend the exposure well beyond the swallow. Halloween is a worked example of everything on this list at once.

Eating sugar with a meal is less damaging than the same sugar alone, because chewing a meal stimulates a large volume of saliva.

Which sugars, and which do not count

• Sucrose (table sugar) is the most cariogenic, but glucose, fructose, maltose and the sugars in fruit juice, honey and syrups all feed the same bacteria. “Natural” is not a dental distinction — honey and fruit juice behave like sugar on teeth.
• Cooked starches — crisps, white bread, crackers — are broken down to sugars by enzymes in saliva, and they lodge in the grooves of teeth. They are a genuine and underrated contributor, and several of them turn up on the list of foods to be wary of.
• Lactose in milk is much less cariogenic, and plain milk is not a decay risk in the way juice is. Milk left in a bottle overnight is a different matter.
• Sugar-free sweeteners are not fermented by the bacteria and do not cause this process. But many sugar-free drinks are still acidic, and that acid attacks enamel directly, without needing bacteria. Sugar-free is not the same as tooth-friendly. Are sugar-free soft drinks better for my teeth than regular soft drinks?
• Xylitol goes one step further: the bacteria take it up but cannot metabolise it, and there is reasonable evidence of benefit in sugar-free gum at sufficient frequency. Does chewing sugar-free gum really help prevent cavities?

What happens if it is not caught

If decay is not managed early enough, it produces cavities, and can lead to infection of the pulp (nerve) — at which point the treatment is a filling or root canal treatment.

Why check-ups do the work symptoms cannot

Decay often progresses with little or no symptoms.

That allows cavities to form and teeth to become infected long before you feel anything — which is precisely why routine examinations and X-rays are recommended. By the time a tooth hurts, the cheap options have generally passed.

The reason is anatomical. Enamel contains no nerve supply, so damage confined to it is genuinely painless. Sensation only begins once decay reaches dentine, the layer beneath — and by then it is usually a filling rather than something that can be arrested. Decay between teeth is also invisible to the eye, which is why radiographs are taken at intervals: that is where much adult decay begins and it cannot be seen any other way.

Caught in enamel, early decay can be reversed — with fluoride, better cleaning and reduced sugar frequency, the surface can remineralise. That window is the entire argument for check-ups, and it closes without any warning to the patient.

The gum disease pathway

If bacteria are not removed in time, they can also spread to the gums, causing irritation and periodontal disease.

Gingivitis — the early stage — can be resolved with good oral hygiene and professional cleans. It is reversible.

Periodontitis — advanced gum disease — requires more complex treatment to prevent deterioration to the point of permanent tooth loss, and is often managed with a periodontist.

Signs of gum disease: red, itchy or swollen gums that bleed easily when eating, brushing or flossing.

Bleeding gums are the signal that separates the reversible stage from the one that is not. They are worth acting on.

One honest qualification: sugar's role in gum disease is indirect. Gum disease is driven by plaque left undisturbed at the gumline rather than by diet as such — you can develop it on a sugar-free diet if you do not clean between your teeth. Sugar makes plaque grow faster and thicker, which makes it worse; it is not the primary cause.

Mitigating sugar without eliminating it

It is impractical to cut sugar out of the diet entirely. What is possible:

• Check nutrition labels for sugar content — and look for the sugars line under carbohydrates, not the ingredient list alone. Sugar appears under dozens of names: sucrose, glucose, fructose, maltose, dextrose, corn syrup, invert sugar, molasses, malt extract, fruit juice concentrate, agave, rice syrup.
• Avoid snacking throughout the day — frequency matters more than quantity
• Keep hydrated with plain water, especially before and after eating
• Use straws for sugary drinks, or choose sugar-free alternatives
• Finish rather than sip. If you are going to have it, have it and be done.
• Confine sweet things to mealtimes, where saliva flow is already high.
• Nothing sweet after brushing at night. Water only.
• Rinse with water afterwards — but do not brush for an hour after anything acidic, because softened enamel abrades.
• With children, name the pattern rather than the food — it is the between-meal grazing that does the damage.

And the routine that handles the rest

• Floss, to remove bacteria from between the teeth and under the gums
• Brush twice a day with a fluoride toothpaste — and spit rather than rinsing, so the fluoride stays on the teeth
• Drink fluoridated tap water
• Attend regular examinations and professional cleans

The two halves work together: reducing the fuel, and removing the bacteria that would use it.

Who is at higher risk

The same diet does not carry the same risk for everyone. Ask about your own if any of these apply:

• Dry mouth, from medication, medical conditions or previous radiotherapy — the single biggest amplifier, because it removes the repair mechanism
• Gum recession and exposed root surfaces, which dissolve at a higher pH than enamel
• Orthodontic appliances, which make cleaning harder
• A history of frequent fillings
• Deep grooves in the biting surfaces of back teeth, where sealants may be worth discussing
• Reflux or frequent vomiting, which add direct acid
• Limited dexterity, which makes effective cleaning difficult

When to be seen

• Sensitivity to cold or sweet that is new or worsening
• A visible hole, dark mark, or a tooth that catches floss
• Food packing between the same two teeth repeatedly
• Gums that bleed when brushing or flossing
• Pain lingering more than a few seconds after cold, or pain that wakes you — this suggests the pulp is involved and should be assessed promptly
• Facial swelling, or fever with dental pain — a medical emergency; present to an emergency department or call 000. In hours, emergency dentistry is the right door.

Common questions

Standing in the supermarket, how do I actually read the label?

The Australian Dental Association's consumer site (teeth.org.au) gives a usable rule, and it is not the one most people use.

Use the per-100-gram column, not the per-serve column. The ADA's reasoning: the 100 g column lets you compare “apples with apples”, whereas “the serving size is set by the manufacturer so it can be different between products” — which makes per-serve figures useless for comparison. Then, in that column:

• 5 grams of sugar or less is BEST
• between 5 g and 10 g is OKAY
• over 15 g — “TRY TO FIND A HEALTHIER ALTERNATIVE”

Two more things from the same source. Added sugar is usually not stated at all, so you have to read the ingredient list, where “the closer an ingredient is to the top of the list, the more of it that is present” — and sugar “can be called over 50 different names”. And to convert: one teaspoon of sugar equals 4 grams, so the grams figure divided by four is the number of teaspoons.

One limitation worth knowing. A label tells you nothing about acid. The ADA's policy is explicit that sugar-free confectionery is a reasonable alternative only “without added acids” — and a sugar-free drink with citric or phosphoric acid in it still dissolves enamel directly, with no bacteria involved.

Is the Health Star Rating any use for choosing between products for my teeth?

A little, but not much, and it is worth understanding why.

The ADA describes the Health Star Rating as a voluntary labelling system running in Australia and New Zealand since 2014, rating packaged food and drink from half a star to five stars using a calculator that weighs several nutrients and ingredients — and, importantly, that the rating shows how healthy a product is “compared similar products”.

That is the catch for teeth. It is a whole-of-nutrition score benchmarked within a category, not a decay score. A high rating within the biscuit aisle is still a biscuit. And because the calculator does not assess acidity or how often you will eat the thing, it cannot see the two factors that matter most for enamel — the frequency of exposure, and whether the product is acidic in its own right.

Use it to choose between two similar products. Do not use it to decide whether to have the product at all.

Can medicines and vitamin supplements cause decay?

Yes, by two separate routes, and the ADA states both. Its policy notes that “medications, including over-the-counter vitamin and mineral tablets, may include sugars (particularly those that are chewable and dissolved in the mouth) or contribute to dry mouth, both of which can contribute to tooth decay or softening and loss of tooth structure”.

The chewable and dissolvable forms are the ones to look at, because they are held in the mouth by design — which is the same slow-exposure pattern described under frequency above. A chewable vitamin taken daily at bedtime is a nightly acid attack that nobody has counted.

The second route matters more if you take several medicines. Reduced saliva removes the repair half of the cycle entirely, and it is the single largest amplifier of dietary risk.

Two practical steps. Ask your pharmacist whether a sugar-free formulation of the same thing exists — the ADA's own position is that “the pharmaceutical industry should be encouraged to provide sugar-free formulations or minimise sugar content for medications taken orally”, so it is a reasonable question. And bring your current medicine list to your dental appointment, because the dry-mouth risk changes what interval and what preventive measures are appropriate. Never stop or change a prescribed medicine on dental grounds — that is a conversation for the prescriber.

Is any fluoride toothpaste enough, or does the strength matter?

The strength matters, and there is a figure to check on the tube. The World Health Organization, setting out how caries develops, names “toothbrushing with fluoride toothpaste containing 1000-1500 ppm concentration” as the plaque-removal step whose absence, alongside high free-sugar intake, leads to decay.

So a paste below that band — which includes many children's pastes, some “natural” brands, and anything fluoride-free — is not delivering what that recommendation assumes. The concentration is on the packaging, usually as ppm or as a percentage of sodium fluoride or sodium monofluorophosphate.

Children are a deliberate exception rather than an oversight: lower-fluoride pastes and smaller amounts are used at younger ages to limit swallowing, which is a separate judgement your dentist can make for your child's age and decay risk. For an adult, there is rarely a good reason to be below 1000 ppm.

My children drink fruit juice rather than soft drink. Is that better?

Not by as much as most parents expect, and the ADA has surveyed exactly this gap. Its consumer research found that 85 per cent of parents know soft drinks, energy drinks and fruit juice lead to decay — and yet 26 per cent of children have fruit juice daily, 37 per cent have two to five fruit juices a week, and 37 per cent have two to five soft drinks a week. The ADA's own conclusion is blunt: parents “think juices have health benefits”, and “kids are better off having a piece of fresh fruit rather than drinking shop-bought juice”.

Dentally, juice sugar is free sugar. The WHO definition puts “sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates” in the same category as sugar added from the bowl. Whole fruit is different, because the sugar is inside plant cell walls and comes with fibre that demands chewing — and chewing raises saliva.

Two age-specific rules from the same sources. The WHO recommends that children under two years of age should not consume any sugar-sweetened beverages at all. And the ADA advises that for infants and babies, “sleeping with sweetened pacifiers/dummies, food or bottles with products containing sugar, including milk and fruit juices, should be discouraged” — note that this one includes plain milk, because of how long it sits there overnight.

At the other end of life the advice tightens again for a different reason: the ADA singles out older people because of “the increased risk of caries from reduced saliva flow and more exposed root surfaces”.

For scale on the drink itself, the ADA notes that one can of soft drink contains, on average, ten teaspoons of sugar — “1.5 times the daily sugar intake recommended by the WHO”.

Would a sugar tax actually reduce decay, or is that just politics?

Both the WHO and the ADA have taken a position, which is more than can be said for most dietary debates.

The WHO includes dental caries in its economic analysis of taxing sugar-sweetened beverages and “strongly recommends implementing SSB taxes”, treating it as a cost-effective measure to reduce sugar consumption. The ADA goes further into specifics: “a tax on sugar sweetened drinks reduces the consumption of soft drinks and is a cost-effective method of decreasing dental caries”, and its policy asks that money raised fund “health promotion and oral care for disadvantaged Australians”. Australia does not currently have such a tax.

The WHO also frames the problem as partly commercial rather than purely individual, pointing to “the strategies used by some private-sector actors to promote products and choices that are detrimental to health”, including the marketing of high-sugar food and drink.

One caution against reading reformulation as a solution. The WHO advises against using non-sugar sweeteners for weight control or to reduce the risk of non-communicable disease — that advice is about general health rather than teeth, and it does not contradict the point above that sweeteners are not fermented by oral bacteria. Swapping sugar for a sweetener can be a genuine dental improvement while being no help at all on the wider health question, and the acid in the drink is unchanged either way.

Related reading

What does sugar actually do to your teeth? · What a cavity actually is · How does tooth decay develop? · Can you reverse tooth decay? · What dental decay is · How your diet affects your teeth · Six foods to avoid for healthy teeth · What are sports drinks really doing to your teeth? · What is gum disease? · Dental Cleans and Hygienists

Practical details

Written by Dr Avi Aggarwal, Smile Solutions.

We are at Level 1, 220 Collins Street, Manchester Unity Building, Melbourne VIC 3000. Phone 13 13 96, or theteam@smilesolutions.com.au. Monday–Friday 8.00am–6.00pm, Saturday 8.30am–1.30pm, Sunday by appointment.

Registration for any practitioner can be verified free on the AHPRA public register at ahpra.gov.au.

Published 14 October 2020. Prevalence figures are as cited at that date; population survey figures are revised over time, and the WHO guidance should be checked at its own source for the current wording. pH and timing figures are typical values reported in the literature, not measurements of any individual. Children's consumption figures quoted in the questions above are from the ADA's consumer research and its 2024 Children and Young People Oral Health Tracker, and label thresholds from the ADA's teeth.org.au consumer material.

General information only — it is not a diagnosis, a treatment plan, a quote or a promise of any particular clinical outcome, and it does not replace advice from your treating practitioner. Nothing here is dietary or medical advice; decisions about diet, particularly where diabetes or another medical condition is involved, belong with a qualified dietitian or your treating medical practitioner. Your own decay risk and the right check-up and radiograph interval can only be determined after examination.

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