Studies on the measurement of 25-hydroxy vitamin D in human saliva

A competitive protein-binding assay for 25-hydroxy vitamin D (25-OHD) in saliva has been established by adaptation of that previously described for 25-OHD in serum (Fairney et al. 1979). Random values of salivary 25-OHD in patients attending hospital for venesection showed a wide range of results (105-1000 pg/ml, n 55). These values corresponded to 1.2% of the total serum values with which they showed a significant relation (r 0.45, P less than 0.001). There was no relation between salivary 25-OHD and measured serum free 25-OHD in eighteen pairs of saliva and serum studied. Studies in two individuals showed that salivary 25-OHD values varied throughout the day and that a vitamin D load (19.5 micrograms), given as pickled herrings at lunch, produced a marked rise in 25-OHD values 5-8 h later. Diurnal profile studies of salivary 25-OHD in Caucasian and Asian 11-year-old male schoolchildren showed lower values in Asian children eating a vegetarian diet, and a significant variation with time and ethnic group (P less than 0.001). It is concluded that 25-OHD is present in saliva and that the values vary throughout the day. The values obtained may relate to dietary intake of vitamin D and the subject's ethnic origin.