Oral health is integral to overall health and well-being. Tooth decay or dental caries, an infectious disease, is a common cause of poor dental health, especially in children. Although sugars have been associated with dental caries, all types of fermentable carbohydrates can promote cavity formation. What’s more, proper dental hygiene is more effective in preventing tooth decay than changes to nutrition habits.

Causes of Tooth Decay

The etiology of tooth decay is complex and multi-factorial. Nutritional status, oral hygiene, fluoride exposure, dietary habits, heredity, socioeconomic status, general health and use of medications can all play a role.

However, a direct relationship between diet and dental caries is accepted. All fermentable carbohydrates, including sugars and starches, contribute to dental caries formation. Starches are broken down to sugars in the mouth by salivary amylase. Thick plaque bacteria, present on tooth surfaces, metabolize sugars to form organic acids. These acids lower the pH of plaque. Although tooth enamel is generally hard and wear resistant, it is slightly soluble in acids. Thus, the presence of these organic acids causes the tooth enamel to begin to dissolve or demineralize. The longer the pH remains low or acidic, the more likely enamel erosion will occur.

Teeth surfaces are repeatedly attacked by acids and then repaired by the action of saliva. Saliva contains many cario-protective components that help defend teeth against erosion including calcium and phosphate, fluoride, buffers and anti-microbial agents. It therefore neutralizes acids, dilutes sugars in food as well as assists in repairing losses to teeth surfaces through remineralization. Unfortunately, this ‘normal’ remineralization process is very slow. Thus, if demineralization of enamel exceeds the remineralization repair process, caries formation will occur.

The frequency and severity of attacks on teeth surfaces can be influenced by a number of factors. For example, “grazing” on food and drink for long periods of time increases exposure of bacteria to fermentable carbohydrate and therefore increases the exposure of teeth to acids. Similarly, foods that stick to teeth will increase exposure of teeth to acids since they remain in the mouth longer. Other factors include the amount and virulence of bacteria present, the abundance and make-up of saliva, the inherent resistance of teeth to acid and the type of food ingested.

Caries Prevention

Oral Hygiene and Fluoride Use

Though sugars and other fermentable carbohydrates contribute to tooth decay, several studies have shown that in countries where proper oral hygiene is followed and adequate fluoride exposure exists, caries prevalence has decreased despite increases in sugar consumption. Furthermore, if carbohydrate-containing foods are eaten frequently but oral hygiene is maintained and fluoride used, caries are not likely to form. The use of fluoride in drinking water and toothpaste provides strong protecton against dental caries. Therefore, prevention should focus on proper oral hygiene and adequate fluoride use, rather than fermentable carbohydrates alone.

The Canadian Dental Association encourages Canadians to brush after meals, floss regularly and visit a dentist every six months for a check-up. When brushing is not possible, rinsing with water can help limit the effect of cariogenic bacteria on teeth.

Fluoride helps protect teeth in three ways: it inhibits plaque, it defends tooth enamel from demineralization, and it speeds-up and improves remineralization. Thus, Health Canada endorses the fluoridation of drinking water at the optimum level of 0.7 mg/L, as a safe and effective way to reduce tooth decay. In fact, addition of fluoride to municipal water supplies has been shown to reduce the rate of dental caries in children by 35-50%, and by 30% in adults. However, the ingestion of too much fluoride can result in fluorosis --a cosmetic condition that appears as white specks on teeth -- which occurs predominantly in younger children. For recommendations for the use of fluoride in infants and children, visit the Canadian Pediatric Society.

Sugars and Other Carbohydrates

Frequency - Although proper oral hygiene and fluoride use are the primary tools for preventing tooth decay, dietary changes can help. The goal should be to limit the frequency and severity of acid attacks on teeth. It is not the total amount of sugars and starches ingested that matters most in caries formation but the frequency of carbohydrate consumption. Sugars and starches can be consumed without deleterious effects when they are ingested as part of main meals rather than eaten continuously throughout the day. Thus, spacing meals at least two hours apart allows dental plaque pH time to return to neutral.

Source - All fermentable carbohydrates, whether from the sugar bowl, fruits, vegetables, milk or grain products, break down to sugars in the mouth and can lead to tooth decay. 

Though the mechanism is unclear, chewing on high-protein foods in combination with fermentable carbohydrates may protect against dental caries. Also, the chewing action as well as the combination of raw and cooked foods in the mouth can increase salivary production, which minimizes the effect of fermentable carbohydrates on teeth.

Form - Carbohydrate-containing foods that are sticky and that adhere to teeth are potentially more cavity-causing because they are difficult to brush away and may remain in the mouth for longer periods of time. Examples of foods that stick to the teeth include caramels and dried fruit, while foods such as bread, potato chips and crackers are more likely to stick between the teeth. However, compared to drinking fruit juices, eating whole fruits have similar effects on caries development. 

Other Dietary Recommendations

Infants - Tooth decay can develop in infants who are given a bedtime-bottle filled with fermentable-carbohydrate containing fluid such as fruit juice or milk. This condition, commonly called early childhood tooth decay, can also result from mothers allowing infants to nurse at the breast while sleeping. It can lead to loss of baby teeth, crowded or crooked permanent teeth and speech difficulties. To prevent this, a baby should never be put to bed with a bottle. However, if the baby is accustomed to this practice, the bottle’s contents should be replaced with water.

For further information, see Cor van Loveren's contribution to our 2015 resource Carbohydrate News - Sugars and Health: The Current Science.