Diet and Nutrition Prevention of Chronic Diseases

9. Dental diseases

• 9.1 Are dental diseases a growing problem?
• 9.2 How can diet affect dental diseases?
• 9.3 Dietary sugars and dental caries
• 9.4 Dietary factors which protect against dental caries
• 9.5 How could dental diseases be prevented?

9.1 Are dental diseases a growing problem?

In developed countries, dental diseases account for 5% - 10% of total health care costs, exceeding the cost of treating cardiovascular disease, cancer, and osteoporosis.

Dental diseases include among other things:

• caries which are cavities resulting from the action of bacteria on sugary foods,
• dental erosion which is the loss of hard tooth tissue (enamel and dentine) caused by acid attack,
• periodontal disease which refers to bacterial infections of the gums.

Despite the marked overall decline in dental caries over the past 30 years (perhaps due to exposure to an adequate amount of fluoride) the prevalence of dental caries remains unacceptably high in many developed countries.

In most developing countries, the prevalence rate of dental caries is relatively low and more than 90% of caries are untreated. However, there has been a recent increase in the prevalence of the disease. This increase is thought to be linked to changing diets, and particularly to an increase in sugar consumption without exposure to sufficient amounts of fluoride. Overall prevalence of dental caries in children remains high.

Table 12: Trends in levels of dental caries in 12-year-olds

The number of people who have few or no natural teeth has declined over the past 20-30 years in several developed countries. As older people generally keep their teeth for longer, the problem of root caries is likely to become a significant public health concern in the future. As the average age of the population continues to increase, the number of people affected by tooth loss will grow.

Table 13: Prevalence of toothlessness in older people throughout the world

Dental erosion, which is related to diet, is a relatively new dental problem in many countries throughout the world. In some populations it is estimated that approximately 50% of children are affected.

Denatal diseases have an impact on self-esteem, eating ability and nutrition.

This text is a summary of: WHO/FAO Diet, Nutrition and the prevention of chronic diseases
Section5.6.1 Background – 5.6.2 Trends 

9.2 How can diet affect dental diseases?

Bacterial fermentation of dietary sugars in the mouth is responsible the loss of minerals from the teeth that can lead to the formation of caries. While the development of caries requires the presence of both sugars and bacteria, it is also influenced by the susceptibility of the tooth, the type of bacteria, and the quantity and quality of the saliva. Deficiencies of vitamins D and A have been shown to affect the natural development of the teeth, which can make them more susceptible to decay. Under nutrition, coupled with a high intake of sugars, may exacerbate the risk of caries.

Whilst severe vitamin C deficiency can result in inflammation of the gums, the most important factor in preventing periodontal disease is good oral hygiene. Undernutrition increases the severity of oral infections, such as gum disease.

Dental erosion can be caused by dietary acids such as those found in fruit drinks, soft drinks (including sports drinks), vinegar, citrus fruits and berries. Studies have shown that tooth enamel is softened within one hour of exposure to cola, but that this softening may be reversed by exposure to milk or cheese.

Summary of strength of evidence linking diet to:

Table 14: Dental caries

Table 15: Dental erosion

Table 16: Enamel development defects

Table 17: Periodontal disease

This text is a summary of: WHO/FAO Diet, Nutrition and the prevention of chronic diseases
Section 5.6.3 Diet and dental disease 

9.3 Dietary sugars and dental caries

Sugars are the most important dietary factor in the development of dental caries.

Worldwide studies on human populations show an association between sugar consumption and level of dental caries. Isolated communities that consume a small amount of sugar have a very low level of this disease. Groups of people with a high exposure to sugars have a higher level. A strong correlation exists between both the amount and frequency of sugar consumption and the development of caries, even in countries that use preventative measures such as water fluoridation. In addition to solid foods, consumption of sugary drinks also increases the risk of developing dental cavities.

Studies have shown that starches are generally a much lower risk factor in developing dental caries than sugars. However, when starches are cooked or combined with sugars, the risk is greater.

As part of a normal mixed diet there is little evidence that fruit causes caries . Animal studies have shown that when fruit is consumed in very high frequencies (e.g. 17 times a day) it may induce caries.

The link between dietary sugars and dental caries is supported by a large body of evidence. However, the limitations of the different types of studies should be considered when interpreting results:

• Caries develop over time and therefore the dietary factors, several years previous to the appearance of caries, should be considered.
• Animals have different teeth than humans and therefore the results of animal studies are not always transferable to human cases.
• Studies sometimes measure the amount of acid produced from a food when bacteria in the mouth ferment it, in order to estimate the risk of caries, but such studies do not consider protective properties, such as effects on the flow of saliva

This text is a summary of: WHO/FAO Diet, Nutrition and the prevention of chronic diseases
Section 5.6.3 Diet and dental disease, Dietary sugars and dental caries 

9.4 Dietary factors which protect against dental caries

Fluoride is the most effective preventative measure against the development of dental caries. The addition of fluoride to drinking water reduces dental caries in children by between 20% and 40%, but does not eliminate the risk of dental caries altogether. Thus, restricting consumption of sugars still has a role to play in the prevention of caries, even in situations where there is widespread use of fluoride.

Excess ingestion of fluoride during enamel formation can lead to dental fluorosis, particularly in countries that have high levels of fluoride naturally present in water supplies.

Certain other dietary components have been shown to have protective properties against dental caries:

• Cow’s milk (cheese) contains calcium, phosphorus, and casein which are believed to inhibit caries.
• Wholegrain foods require more chewing thereby stimulating the flow of saliva and protecting against caries.
• Peanuts, hard cheeses, and chewing gum also stimulate salivary flow and protect against caries.
• Black tea extract increases fluoride concentration in tooth plaque thereby reducing the risk of developing caries linked to a diet rich in sugars.

Studies have associated breastfeeding with lower levels of dental caries in early childhood. This is likely to be due to the fact that breastfed infants consume less sugar than infants fed formula milk to which free sugars are often added.

This text is a summary of: WHO/FAO Diet, Nutrition and the prevention of chronic diseases
Section 5.6.3 Diet and dental disease, Influence of fluoride  and
5.6.3 Diet and dental disease, Dietary factors which protect against dental caries & Breastfeeding and dental caries  

9.5 How could dental diseases be prevented?

The main diet-related recommendations for reducing the risk of dental diseases are:

• Ensure that the intake of free sugars contributes on average less than 10% to the daily energy intake. Indeed, the occurrence of dental caries is lower in countries where the average daily consumption of sugars is below 40-55g per person which represents 6-10% of the daily energy intake.
• Restrict the frequency of consumption of foods and drinks that contain free sugars to a maximum of 4 times per day.
• Assure adequate exposure to fluoride to protect against caries
• Avoid nutrient deficiencies that can contribute to dental diseases.

This text is a summary of: WHO/FAO Diet, Nutrition and the prevention of chronic diseases
Section 5.6.5 Disease-specific recommendations