Caffeine and stress alter salivary alpha-amylase activity in young men.

OBJECTIVE We examined the effects of caffeine and a psychological stressor on salivary alpha-amylase (sAA) in healthy young males (age 18-30 years) who consumed caffeine on a daily basis. METHODS Using a between-subjects, double-blind, placebo-controlled design, 45 participants received either 200 or 400 mg of caffeine (Vivarin) or placebo, rested for 20 min, and then performed 20 min of mental arithmetic. Saliva samples (assayed for sAA and caffeine), blood pressure, and heart rate were taken before (baseline) and 15 min after the math stressor (stress). RESULTS Baseline sAA activity did not differ among the treatment groups; however, there was a statistically significant time by caffeine group interaction. Changes in sAA activity across the session were dependent on the amount of caffeine consumed. Following the challenge period, sAA activity among the placebo group was the lowest and sAA activity among the 400 mg treatment group was the highest. Separate repeated-measures ANOVAs conducted for each drug treatment group revealed that sAA activity increased in response to stress and caffeine (i.e., 200 and 400 mg groups) but not to stress alone (i.e., placebo group). CONCLUSIONS Findings provide evidence for acute sAA changes in response to caffeine and stress in habitual caffeine users.