Circadian variations in the flow rate and composition of whole saliva stimulated by mastication

Abstract

Samples of whole saliva stimulated by chewing rubber bands were collected from 15 subjects at every hour of the day and night. Circadian rhythms were demonstrated most consistently in flow rate, sodium, chloride, phosphate (total and inorganic) and nitrogen concentrations. Calcium concentration rhythms were demonstrated in 11 subjects, potassium and carbohydrate in 9. Only one third of subjects showed a rhythm in protein concentrations; a result possibly due to loss of protein during storage of the samples. Sodium, chloride, phosphate and calcium concentrations were highest in early morning but flow rate was greatest in the evening, as was nitrogen concentration and, less consistently, potassium concentration. The circadian range of values was 60–75 per cent of the mean values except for a slightly lower range for phosphate and a limited range for potassium (25 per cent) and nitrogen (32 per cent). Samples of whole saliva collected in the afternoon will be less variable than at other times since many components have maximum or minimum concentrations near that time.