Effect of flavored beverage crystals on salivary cortisol enzyme-immunoreactive assay measurements

We examined the effects of using flavored drink crystals as a salivary stimulant on salivary cortisol values. The effects of both amount and method of flavored crystal administration on cortisol values were evaluated using a high sensitivity enzyme immunoassay (EIA) kit to measure cortisol. Repeated saliva sampling, one sample without the drink crystal stimulant, followed immediately by a second sample using the drink crystal stimulant, allowed direct analysis of the effect of the stimulant on cortisol values. Repeated sampling, with the stimulant used when obtaining both the first and second samples, allowed analysis of the repeatability of cortisol measurements using the drink crystals. The results suggest that the use of drink mix crystals as an oral stimulant causes a small increase in measured cortisol values, as well as an increase in the variability of these values. The results also suggest that the effect of drink crystals is sufficiently regular so that it will not distort either within or between subject comparisons as long as there is consistency in use or non‐use of the stimulant. © 2005 Wiley Periodicals, Inc. Dev Psychobiol 47: 189–195, 2005.