Soy milk is prized for its high nutritional content and ease of substitution with traditional dairy products. Made by soaking, then grinding and cooking soybeans, soy milk arrived in America in 1979 and is popular in the vegan/vegetarian, lactose intolerant and health-conscious communities. However, a recent study undertaken at the University of Melbourne Dental School shows soy milk may have adverse implications for oral health.
The study examined soy milk's effect on the post-meal process during which bacteria form biofilms on the tooth surface and secrete acid. Ordinary cow's milk does not produce a high degree of acidity due to its difficult-to-ferment sugars and caseins, proteins naturally found in milk which form a protective film on the enamel.
Soy milk, on the other hand, lacks these caseins, and contains carbohydrates that are readily fermented by oral bacteria. The Melbourne study found that oral bacteria cultures produced six times as much acid when inoculated with soy milk as compared to cow's milk. This finding is upsetting to many experts on oral health and nutrition, but the researchers caution that these results have not yet been studied in a living organism, just on the agar plate so far.
However, another important point is that soy milk often contains a significant amount of added sugar. In fact, over 90% of the soy milk sold in the US is sweetened in some way, most often with simple sugars that are easily fermented by the oral bacteria.
Based on the results of this study, it seems that lactose-intolerant patients may benefit from switching to unsweetened nut or coconut milk, and consider avoiding soy milk altogether.
Science, L. (2017). Is Soy Milk Bad for Teeth?. Live Science. Retrieved 3 April 2017, from http://www.livescience.com/36556-soy-milk-teeth-cavities.html