EFFECTS OF DIET ON SALIVARY PHOSPHATE

¹ Department of Physiological Chemistry, Teachers College, Columbia University, New York City

The chemical law of mass action, and the fact that tooth enamel is composed of Ca₃(PO₄)₂, suggest that the solution equation —Ca₃(PO₄)₂Ca + PO₄— can be arrested by surrounding the tooth with a medium (e.g., saliva) rich in PO₄ ions, as suggested by Klein, Kruse, and McCollum (1). It is probable, as suggested by previous observers, that if this is the mechanism, or one of the mechanisms by which caries is controlled, it cannot be continuously operative, for in that case a person with permanently low salivary phosphate would have severely eroded teeth.

Our tests indicate that it is possible, by dietary means, temporarily to reduce salivary P and, during this period, to provide thereby conditions favorable to solution of enamel. They indicate that salivary P is (a) lowered by rapid ingestion of sugar, or of less readily digested carbohydrate, or of protein food; (b) unaffected by ingestion of fats; and (c) increased by ingestion of inorganic phosphate.

The foregoing data indicate that temporary changes in salivary P of considerable magnitude are producible by changes in diet. The data are not offered as proof that the defensive mechanism postulated by Klein, Kruse, and McCollum (1) is a factor in caries prevention. In fact, the rôle of P intake as affecting caries prevention has been recently challenged by Shelling and Asher (8). The conditions necessary for enamel solution have been lately reported by Forbes (9), who has indicated that the composition of fluid surrounding a tooth can influence enamel solution. In the mouth the environmental fluid is saliva, and our studies indicate, in accord with the findings of others, that diet can influence the composition of this secretion.

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