A new understanding of the relationship between sugars, dental caries and fluoride use: implications for limits on sugars consumption

Abstract

Objective: To examine the quantitative relationship between sugar intake and the progressive development of dental caries.

Design: A critical in-depth review of international studies was conducted. Methods included reassessing relevant studies from the most recent systematic review on the relationship between levels of sugars and dental caries. Reanalysis of dose-response relationships between dietary sugars and caries incidence in teeth with different levels of caries susceptibility in children was done using data from Japanese studies conducted by Takeuchi and co-workers.

Setting: Global, with emphasis on marked differences in both national sugar intake and fluoride use and preferably where one factor such as sugar intake changed progressively without changes in other factors over a decade or more.

Subjects: Children aged 6 years or more and adults.

Results: Caries occurred in both resistant and susceptible teeth of children when sugar intakes were only 2-3 % of energy intake, provided that the teeth had been exposed to sugars for >3 years. Despite increased enamel resistance after tooth eruption, there was a progressive linear increase in caries throughout life, explaining the higher rates of caries in adults than in children. Fluoride affects progression of caries development but there still is a pandemic prevalence of caries in populations worldwide.

Conclusions: Previous analyses based on children have misled public health analyses on sugars. The recommendation that sugar intakes should be ≤10 % of energy intake is no longer acceptable. The much greater adult burden of dental caries highlights the need for very low sugar intakes throughout life, e.g. 2-3 % of energy intake, whether or not fluoride intake is optimum.

Fig. 1

Regression lines of the correlation between annual sugars consumption and annual caries incidence rates by type of teeth^{( 12 )}. The average caries rates on a log-linear scale are shown for the two first molars (tooth number 6) with the bar at the top representing the molars in the upper jaw and the bar at the bottom representing those in the lower jaw; the average caries rates for tooth number 7 relate to the second upper and second lower molars. Tooth 1 is the central lower and tooth 2 the lateral lower incisors. Note the incisors are more resistant than the molars, which show the same incidence of cavitation at about half the sugar intake needed for the incisors. Sugar intakes of 5 kg/capita per year are equivalent to about 2·7 %E and 15 kg/capita per year to 8·2 %E, where %E is percentage of energy intake. (Adapted from Sheiham^{( 12 )})

Fig. 2

The incidence rates (Mx) for different post-eruptive years, from 1 to 12 years, and annual sugar consumption for the upper and lower first molars (tooth number 6), showing the slowly increasing resistance of teeth to sugar-induced caries after their eruption but with a log-linear effect still evident in older teeth that have been exposed for 10–12 years^{( 15 )}. Mx, the annual caries incidence rate=number of teeth newly attacked by caries during x years of post-eruptive age/number of sound teeth at x years of post-eruptive age. (Adapted from Takeuchi^{( 15 )})

Fig. 3

Cumulative numbers of upper central teeth (a) and first molar teeth (b) affected by caries per 1000 teeth plotted on a log scale, by post-eruptive tooth age and annual sugars consumption^{( 16 )}. In 1971, when these data were published, the average national sugar intake in Japan from FAO food balance sheets was about 11·7 %E (≈21·4 kg/year), where %E is percentage of energy intake. (Adapted from Takeuchi et al.^{( 16 )})

Fig. 4

Mean numbers of decayed, missing and filled teeth (DMFT) in Japan from nine national dental surveys conducted at 6-year intervals from 1957 to 2005 and presented sequentially for each age group from 1957 to 2005, showing the increase in DMFT with age and that most of the increase in DMFT occurred in adults^{( 35 )}. FAO food balance sheet data suggest sugar intakes of 7 %E in 1961 increasing to 11·2 %E in 1985 and with intakes of 9·6 %E in 2005, where %E is percentage of energy intake. (Adapted from Kawashita et al.^{( 35 )})

Fig. 5

Trend lines showing increasing levels of caries of individuals when aged 5 years and followed through into adulthood until they are 32 years of age. Each line depicts the caries level of an individual, where DMFS is decayed, missing and filled surfaces^{( 36 )}. (Published with permission)