Evidence for a relationship between diet and dental caries
(sugar is cariogenic)Evidence for a relationship between diet and dental caries comes from different types of studies:
Human epidemiological observation studies
Human intervention studies (clinical trials)
Animal experiments
Plaque pH studies
Enamel slap experiments
Incubation studies
World-wide epidemiological observation studies:
Sugar intake and levels of dental caries can be compared among countries levels. Sreebny (1982) correlate the dental caries experience of primary dentition (dmft) of 5 and 6 years olds with sugar supplies data of 23 countries, and dental caries experience (DMFT) of 12 years olds with sugar supplies data of 47 countries. For both age groups, significant correlations were observed.From these data it was calculated that for every 25g of sugar per day, one tooth per child would become decayed, missing or filled. In countries with an intake of sugar 18 Kg/person/year (equivalent to ~50 g/person/day) caries experience was consistently below DMFT 3. The countries with sugar supplies in excess of 44 Kg/person/year (about 120g/person/day) had significantly higher levels of caries.
Do dental caries patterns change following changes in availability of dietary sugars?
War time diet.Populations that had reduced sugar availability during the second world war showed a reduction in dental caries, such as Japan, sugar consumption fell from 15 kg/person /year to 0.2 kg/person/year. Which subsequently increased again when the restriction on sugar was lifted.
Caries in group of people before and after increase in sugar consumption.
Eskimos. Many studies stated that Eskimos living on their natural diet have low dental caries, but that their dental health declined rapidly after exposure to westernized life style including high sugar western diet.
Sudan and Ethiopia. In a study, it was observed that caries experience in many areas of Sudan was generally low, but higher in Khartoum and Omdurman, where sugar consumption was high.
The Island of Tristan da Cunha. It is a remote rocky island in South Atlantic, 200 inhabitants, dental caries was very low, but since 1940 there was an increase in the trading with western society and increase availability of sugar, so that dental health was deteriorated. Because of volcanic eruption, they were evacuated to England between 1961-1963.
Studies on groups of people eating low amount of sugar.
Hopewood house.
This a home in Australia housing about 80 child of low socioeconomic background, children came to the home soon after birth and stay till 12 years of age. The diet was classed as lacto-vegetarian, only whole meal flour was used for bread and biscuits. Sugar and white flour were virtually absent, fluoride intake was low and oral hygiene measures were absent, but surveys revealed low prevalence and severity of dental caries than children of the same age and socioeconomic. When the children left the house at 12 years, their DMFT scores became as other children. This indicates that the diet received till 12 years did not confer any protection from caries development in subsequent years.
Synon Ranch community.
This is a boarding school in California, refined sugar was eliminated from the diet. It was found that 53% of the children aged 5-17 years were caries free.
Patients with hereditary fructose intolerance
This is a rare hereditary disease where there is a deficiency of a liver enzyme fructose 1 phosphate splitting aldolase, and ingestion of fructose or sucrose (which contain fructose) causes severe nausea. There caries experience was very low.
Diabetic patients.
Diabetes mellitus is usually treated by insulin and dietary restriction, although some authors have reported a high caries incidence in diabetics because of increased salivary glucose levels and reduced salivary flow, most surveys show a low caries experience in diabetics because of their dietary restriction.Seventh Day Adventists.
This group restricts the use of refined sugars and sticky desserts. In many surveys, they found that children from SDA had lower dental caries than children of same age group.
Children of dentists.
In UK and many developed countries, children of dentists had a lower dmft, DMFT compared with other children at the same age, this might be due to dietary restriction of sugars which is more effective in prevention compared to fissure sealant, topical fluoride and tooth brushing.
Restriction of sale of sweets in Australian schools
Students in schools restrict selling sweets had lower DMFT values than others.
Groups of people with high sugar consumption
Sugar cane chewerSurveys performed showed that people who habitually chew sugar cane have higher caries experience compared with age matched individuals.
Workers in confectionary industries
Such workers have higher caries experience compared with other workers.
phenyl ketone urea
this is a rare hereditary defect where there is a deficiency of a liver enzyme phenylalanine hydroxylase. Unless diagnosed and treated (with high carbohydrate diet low in phenylalanine) within few weeks of life, a severe mental deficiency may occur, these individuals have higher caries experience.
Children taking syrup medicines for long term
Pediatric medicines are conventionally syrup medicines given for more than 6 months in syrup form, almost sucrose based. In many surveys, they found that children taking syrup medicine for long period had higher caries compared to age matched children never used syrup medicine or those were on tablets.
Human intervention studies:
Vipeholm study
This study was conducted between 1945-1953 on 964 mentally deficient patients in Sweden. Sugars and potential in caries were inducted in three forms:
- non-sticky form
- sticky form
- between meals and sticky form.
The patients were divided into seven groups:
Control group
Sucrose group
Bread group
Chocolate group
Caramel group
8 toffee group
24 toffee group
Results from the study:
Sugar has a topical effect on the teeth
Bread is not as cariogenic as sugar
The amount of sugar is not critical
The frequency of eating is more important
Liquid sweets are not as cariogenic as retentive sweets
Carious lesions occurred despite avoidance of caries
Conclusion of Vipeholm
Consumption of sugar, even at high levels, is associated with only a small increase in caries increment if the sugar is taken up to 4 times a day at meals and none between meals.
Consumption of sugar both between meals and at meals is associated with marked increase in caries increment.
Increase in caries activity, under uniform experimental conditions varies widely from person to other.
Increase in caries activity disappears on the withdrawal of sugar rich foods.
Carious lesions occurred despite avoidance of sugars.
Turku study
A controlled longitudinal study carried out in Finland in the 1970s (Scheinin and Makinen). 125 adults participated in the study, allocated to 3 groups , sucrose group S, fructose group F and xylitol group X, where these types of sugars were added to their diet. The study persisted for 2 years, the amount of consumed sugar was 45 kg/person/year. caries development was the highest in sucrose group followed by F and then X (virtually none).
Animal studies:
Rats were reared under germ free conditions were fed a cariogenic diet, did not develop caries, in contrast to other rats fed on the same diet but not reared under germ free conditions.Another study demonstrated the importance of the local effect of the diet. Rats were allocated into 4 groups, all were fed the same diet, when intact or desalivated rats were fed a cariogenic diet via stomach tube they didn’t develop caries, in contrast, caries developed in the normally fed rats and was much higher in the desalivated rats.
Plaque pH studies:
Plaque pH studies that remove plaque from all areas of the mouth and then measure pH (harvesting method). It must also be considered that plaque pH studies measure acid production from a substrate and do not measure caries development. This means that plaque pH studies take no account of the protective factors found in the starch-rich food.Enamel slab experiments:
Enamel slab experiments use oral appliances that hold slabs of bovine or human enamel. Plaque forms on the enamel slabs that remains in the mouth for 1 to 6 weeks. The slabs are exposed to the dietary factor being tested by either consumption with the slabs in situ or by removal of the appliances several times a day to dip into vessels containing the dietary test substances. Changes in enamel hardness or degree of demineralization may be measured at the end of the experimental period.Incubation studies:
These are simple tests and examine the ability of plaque microorganisms to metabolize a test food into acids. They are done outside the mouth and can be classed as test tube experiments. In some of these experiments, teeth or parts of teeth have been incubated with saliva and substrates and the degree of dissolution of the enamel quantified.Does fluoride eliminate the sugar-caries relationship?
Exposure to fluoride did not totally override the effect of sugar on the diet and that exposure to fluoride, coupled with sugar restriction, has added benefits for caries prevention.In the presence of adequate exposure to fluoride, the intake of free sugars should be limited to 15-20 kg/person/year (equivalent to 44-55g/day). In the absence of fluoride, the intake of free sugar should be below this limit. These values equate to 6-10% of energy intake. The frequency of intake of foods containing free sugars should be limited to maximum of four times a day. The potential financial consequences of failing to prevent dental caries needs to be highlighted, especially to government of countries that currently have low levels of disease, but are undergoing nutrition transition (adopting westernized diet).