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The Rot on Sugar and Tooth Decay

Written by Daniel Roytas, MHSc (Nutrition), BHSc (Naturopathy), Dip. RM, MANTA

Dental carries are one of the most prevalent non-communicable chronic diseases in the world. Refined and processed foods that contain a high level of free sugars, that are either present naturally or added to foods, pose the greatest risk in the development of carries1. The most common types of sugars implicated in the development of carries include monosaccharides (glucose, galactose, fructose) and disaccharides (sucrose, maltose, lactose). The current evidence suggests that the development of dental carries is reduced when the consumption of free sugars is less than 10% of the total dietary energy intake1. It should be noted that dental carries are not eliminated with a reduced free sugar intake below 10%, suggesting that even small amounts of sugar are harmful to our oral health1.

Dental carries are said to develop when sugars come in to contact with oral bacteria. When bacteria metabolises or ferments sugars in the oral cavity, acids are produced, which directly damages and erodes the enamel and dentine of teeth2. This is a commonly accepted mechanism, however what if this wasn’t the sole cause?

In 1958, Steinman et al. conducted a number of controlled experiments investigating the effects of sugar and dental carries in mice. It was found that mice injected with a 20% solution of glucose and fructose developed more dental carries compared to control mice, and more importantly, mice that were fed the sugar solution orally. Interestingly, it was found that when vitamin C or vitamin B6 was added to this solution and injected, the number of mice free from carries increased and the total number of carries in mice decreased3. A few years later in 1961, Luoma reported that rats had significant reductions in the phosphate-carbonate ratio in molar enamel when they were injected with a 15% glucose and 15% fructose solution4. These experiments are rather fascinating, because they show that sugar does not necessarily have to come in to direct contact with the teeth to cause decay.

Although further research is required, this evidence suggests that sugar may rot your teeth from the inside out. The assumption that sugar causes decay from coming in to direct contact with bacteria on the surface of the teeth is unlikely to be the sole contributing factor of tooth decay. When sugar is injected, it completely by-passes the oral cavity and therefore it indicates that sugar is having a far more systemic and deleterious effect on our health than we realise. This then begs the question, if sugar has the potential to rot our teeth from the inside out, what is the true extent of the damage that is being done when sugar comes in to contact with the internal tissues and organs of the human body?

  1. Moynihan P. Sugars and Dental Caries: Evidence for Setting a Recommended Threshold for Intake. Adv Nutr. 2016;7(1):149-156. doi:10.3945/an.115.009365
  2. Touger-Decker R, van Loveren C. Sugars and dental caries. Am J Clin Nutr. 2003;78(4):881S-892S. doi:10.1093/ajcn/78.4.881S
  3. Steinman RR, Haley MI, O’Day P. Intraperitoneal Injections of Carbohydrates to Suckling Rats, and Subsequent Dental Caries. J Dent Res. 1958;37(4):719-721. doi:10.1177/00220345580370041901
  4. Luoma H. The effect of injected monosaccharides upon the mineralization of rat molars. Arch Oral Biol. 1961;3:271-277.
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