Extrinsic sugars plus bacteria cause cavities
The hypothesis that intake of non-milk extrinsic sugars1 continues to be the main threat for dental health is well-supported by the evidence.
The introduction to (Harris et al. 2012) reviews this evidence.
Sugars, particularly sucrose, are the most important dietary aetiological cause of dental caries. The evidence establishing sugars as an aetiological factor in dental caries is overwhelming.
Studies acknowledge that only extrinsic sugars are implicated in this relationship. ("Foods rich in starch, without the addition of sugars, play a small
role in coronal dental caries", (Harris et al., citing Moynihan and Petersen 2004)).
comes from many different types of investigation
including human studies (both observational and intervention),
human plaque pH studies (in which the pH of
plaque is monitored in situ following ingestion of a test
substance), enamel slab experiments (in which slabs of
bovine enamel are fitted in a removable oral appliance and
worn during periods of consumption of experimental diets
and subsequently the level of demineralisation is
measured), animal studies and incubation studies of oral
bacteria and dietary substrates in vitro. (Moynihan and Petersen 2004)
Bacteria do consume processed sugar. From (Moynihan and Petersen 2004):
Streptococcus mutans and Streptococcus sorbrinus are important bacteria in the development of dental caries.
Mutans streptococcal invertase splits sucrose into glucose and fructose, which can be metabolised to produce mainly lactic but also other acids including acetic and formic acid.
Regarding interventions, the claim that introducing dairy into ones diet is helpful is supported by two studies. "Milk and cheese can reduce the effects of metabolic acids and help restore enamel lost during eating" (Harris et al. 2012, citing Aloha et al. 2002 and Kashket et al. 2002).
The systematic review (Harris et al. 2012) found that:
- most of the studies concerning sugar consumption are of relatively weak quality,
- the evidence for dietary advice aiming to change sugar consumption is poor, and that
- further studies in this area should be considered.
This was because there is a dearth of studies examining the advice to change sugar consumption as an intervention and those that do exist have methodological weaknesses. Even though sugar is clearly linked by the evidence through a causal chain to dental cavities, that does not automatically mean that the best (or even useful) intervention is advice to change diet. Possible reasons are poor compliance, improvements masked by simply following toothbrushing advice, etc. The authors conclude that further systematic research needs to be done.
1. Non-milk extrinsic sugars are sugars not incorporated into the cellular structure of foods and not milk sugars (lactose).
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Harris R, Gamboa A, Dailey Y, Ashcroft A. One-to-one dietary interventions undertaken in a dental setting to change dietary behaviour. Cochrane Database of Systematic Reviews 2012, Issue 3. Art. No.: CD006540. DOI: 10.1002/14651858.CD006540.pub2.
Kashket, Shelby, and Dominick P. DePaola. "Cheese consumption and the development and progression of dental caries." Nutrition reviews 60, no. 4 (2002): 97-103.
Moynihan, Paula, and Poul Erik Petersen. "Diet, nutrition and the prevention of dental diseases." Public health nutrition 7, no. 1A; SPI (2004): 201-226.