Real Milk, Plant-based Alternatives, and the Promotion of Healthy Teeth

  • Dairy—“real milk”—is understood to provide some protection against the development of dental caries.
  • The calcium and phosphate in milk contribute to this protection, as well as certain proteins that form a film that protects enamel.
  • Plant-based milk alternatives do not appear to be protective in this way, and may instead contribute to the odds of developing bad teeth.

 

Dentists have plenty to do these days. During the pandemic, for weeks and months at a time, countries have put in place policies that have postponed many a dental check-up. Probably millions. Meanwhile, forced to stay home, people’s diets have shifted. One analysis of the Brisighella Heart Study cohort found that participants ate more yogurt and drank more milk than usual during Italy’s FebruaryApril 2020 lockdown. They also guzzled more sugars and sweets [1]. While no dentist expects the extra sugar and sweets to make their job any easier, the elevated yogurt and milk intake just might, depending that is, on whether individuals consumed dairy milk products or plant-based alternatives.

There is growing evidence that the distinction matters for tooth health. Milk is thought to protect teeth against the formation of caries. However, the emerging data on various forms of plant-based milk alternatives is not so positive. Some findings and patient case studies have prompted dentists to issue warnings to one another in the correspondence pages of professional journals [2].

These concerns emerge in the context of a long history of research into the causes of dental caries. Since 1890, micro-organisms able to ferment sugar have been suspected of playing a role in the formation of caries [3]. Even though milk contains moderate amounts of lactose, it is not thought to damage teeth because its other components have a protective effect. Caries develop when enamel “demineralizes” (or dissolves, such that calcium and phosphate leak out). Thus, conditions are primed for demineralization when the mouth’s pH dips below a threshold—unless a lot of calcium and phosphate are already present in solution [3]. (When immersed in these ions, enamel in fact has been shown to not start dissolving even when the pH drops to 2.5 [4].) The calcium and phosphate content of milk and other dairy products thus gets in the way of potential harm caused by a reduction in pH from the fermentation of lactose. Moreover, milk proteins have an additional teeth-protecting effect. They form a layer over enamel that interferes with the growth of troublesome biofilms.

Nearly 20 years ago, a World Health Organization report gathered the available evidence into a report on the effects of dairy on dental health, and concluded a possible decreased risk of dental caries associated with milk consumption [5]. In the years since that WHO report, writes one recent review of the subject, “observational epidemiological studies have adjusted for potential confounders and have reported that milk consumption is associated with lower caries experience or incidence” [6].

Studies to this effect are numerous. For example, one paper published this year reports an assessment of caries in children as young as three years old. The children in question were attending kindergarten across Poland’s 16 provinces. The study found clear differences in the number and severity of caries among the children who were only given milk or water to drink before bed, and those who were allowed other (sugary) beverages [7].

Yet, research findings such of this are rare for plant-based milk alternatives. More often, warnings emerge out of them. From oats to almonds, milk alternatives are becoming increasingly popular. The constituents of these non-dairy options tend to naturally lack many of the vitamins and minerals in plain milk. Hence, calcium and vitamin D are usually added by manufacturers, though the same cannot be said for iodine—present in real milk but not in most plant-based alternatives—as one compositional analysis recently reported [8]. Iodine is needed for the body to make thyroid hormones, and is important in neurological function.

To be sure, adding calcium to plant-based versions of milk could help to quench the effect of fermented “free” sugars on tooth enamel. However, dentists’ main concern with these products is less obvious, as it does not taste sweet at all. Some of these plant-based alternatives contain starchy carbohydrates that have been associated with the formation of caries. The oats in oat milk, for example, may be broken down to form maltose, a comfortable staple of the plaque bacteria that contributes to caries. This means that even when consumers opt for apparently healthy “unsweetened” versions of some plant-based milk alternatives, they are often likely to be selecting products that are less good for their teeth than plain old milk.

The question now is what to do with dentists’ concerns. Where government advice communicates milk as being promoting of oral health, some kind of specification that this refers to dairy milks would be helpful. There has been some discussion of the dental risks of starchy foods in New Zealand [9] but little elsewhere.

 

1. Cicero A. F. G., Fogacci F., Giovannini M., Mezzadri M., Grandi E., Borghi C., Brisighella Heart Study Group. 2021. COVID-19-Related Quarantine Effect on Dietary Habits in a Northern Italian Rural Population: Data from the Brisighella Heart Study. Nutrients13(2): 309.

2. Weerasinghee S. 2021. Just Plain Milk? Brit Dent J, 230: 496.

3. Bradshaw D. J & Lynch R. J. M. 2013. Diet and the Microbial Aetiology of Dental Caries: New Paradigms. Inter Dent J, 63 (Suppl. 2): 64–72.

4. Gao X. J., Elliot J. C., Anderson P. 1991. Scanning and Contact Microradiographic Study of the Effect of Degree of Saturation on the Rate of Enamel Demineralization. J Dent Res, 70: 1332–1337.

5. Amine, E. K., Baba, N. H., Belhadj, M., Deurenberg-Yap, M., Djazayery, A., Forrestre, T., Galuska, D. A., Herman, S., James, W. P. T., M’Buyamba Kabangu, J. R., Katan, M. B., Key, T. J., Kumanyika, S., Mann, P. J., Moynihan, P. J., Musaiger, A. O., Olwit, G. W., Petkeviciene, J., Prentice, A. M., … Yach, D. (2003). Diet, nutrition and the prevention of chronic diseases. World Health Organization Technical Report Series, (916).

6. Woodward M., Rugg-Gunn A. J. 2020. Chapter 8: Milk, Yoghurts and Dental Caries. Monogr Oral Sci, 28: 77–90.

7. Olczak-Kowalczyk D., Gozdowski D., Turska-Szybka A. 2021. Protective Factors for Early Childhood Caries in 3-Year-Old Children in Poland. Front Pediatr, 15(9):190.

8. Sumner O. & Burbridge L. 2020. Plant-based Milks: the Dental Perspective. Brit Dent J, 11: 1–7.

9. Hancock S., Zinn C., Schofield G. & Thornley S. 2020. Nutrition Guidelines for Dental Care v.s the Evidence: Is There a Disconnect? N Z Med J. 133(1509): 65–72.

 

Contributed by
Dr. Anna Petherick
Departmental Lecturer in Public Policy
Blavatnik School of Government
University of Oxford
www.annapetherick.com