Overestimation of salivary 25-hydroxyvitamin D3 level when using stimulated saliva with gum-chewing

The measurement of 25-hydroxyvitamin D3 [25(OH)D3] in whole saliva can be a noninvasive tool for assessing vitamin D status. Gum-chewing increases salivation and is often used to collect an adequate sample volume of saliva within a shorter time. The aim of this study was to clarify whether the concentration of 25(OH)D3 in whole saliva is influenced by gum-chewing.

Stimulated saliva was collected from healthy volunteers chewing a tasteless and flavorless chewing gum after unstimulated saliva was collected without gum-chewing. The salivary 25(OH)D3 and albumin concentrations were measured.

The salivary 25(OH)D3 concentration was reproducibly measured when saliva was collected without gum-chewing, whereas the concentration was significantly increased by gum-chewing (p<0.05, paired t-test). One of the causes for the gum-chewing-induced increase in the 25(OH)D3 concentration may be the increased amount of protein-bound 25(OH)D3 in whole saliva.

Stimulated saliva by gum-chewing should be used with caution in the measurement of 25(OH)D3. The protein binding rate in plasma is a significant consideration when predicting whether the salivary concentration of a compound is varied by gum-chewing.