Effects of soy and bovine milk beverages on enamel mineral content in a randomized, double-blind in situ clinical study

Abstract

Soy beverages are promoted as healthy alternatives to bovine milk even though they can contain added sugar. ObjectivesTo compare enamel mineral content after consumption of bovine milk or a soy beverage in a double-blind, randomized, cross-over in situ clinical study. Materials and MethodsHuman enamel slabs with subsurface lesions were prepared and inserted into intra-oral appliances worn by volunteers who consumed 200 ml of either bovine milk or a soy beverage over a 60 s period once a day for 15 days. Enamel lesion depth and mineral content were measured using transverse microradiography. Saliva samples were collected immediately after consuming the beverages and calcium, inorganic phosphate and fluoride levels analysed. Data were statistically analysed using a linear mixed model. ResultsDepth of the enamel subsurface lesions increased by 7.1 ± 2.0 μm and mineral content decreased by 47 ± 22 vol% min.μm after consumption of the soy beverage indicating demineralization. However, after consumption of bovine milk the depth of the lesions decreased by 7.6 ± 3.5 μm and mineral content increased by 202 ± 43 vol% min.μm indicating remineralization. The changes were significantly different (p < 0.001) between the two beverages. Fluoride levels were similar in the saliva samples for both beverages, however the calcium and inorganic phosphate levels for the bovine milk group were significantly higher (p < 0.02) than those for the soy beverage group. ConclusionsIn this randomized, double-blind in situ clinical trial consumption of a soy beverage demineralized enamel whereas bovine milk produced remineralization. Clinical SignificanceAlthough soy beverages are promoted as healthy alternatives to bovine milk the added sugar and low calcium bioavailability of the soy drink makes frequent consumption a caries risk. (Trial registration no. ISRCTN19137849).