A study of the development of tolerance for caffeinated beverages.

Abstract

A preliminary test had shown that the rate of parotid secretion was definitely affected by the ingestion of coffee. Normal secretion for 15 min. was first recorded, and this served as a control rate. Then the subject drank 2 cups of coffee and the rate of secretion in the subsequent period was recorded. Warm water and decaffeinated coffee were occasionally substituted. Tests made when both habituated and non-habituated coffee drinkers were used as subjects yielded significant differences between the groups. Accordingly a new group of unhabituated subjects was selected and each subject was given 2 pints of a commercial beverage containing caffeine at a given hour each afternoon. Gradual reduction in parotid flow following the giving of the dosage on successive days was shown.[long dash]A. L. Winsor.