Abstract
Salivary hormone analysis is a non-invasive alternative to blood-borne hormone analysis. The orexigenic hormone
ghrelin has been detected in human saliva, though the relationship between salivary and blood-borne
ghrelin and salivary ghrelin's association with energy intake (EI) and appetite remains unclear. The primary
aim of this study was to compare salivary and plasma ghrelin responses to dairy breakfast drinks varying in
protein content and quantity, and to determine the relationship between salivary ghrelin and EI and appetite.
Participants (n = 25) consumed four test drinks, varying in protein content and quantity, on four separate days in
a double-blind randomized controlled study. Salivary and plasma total ghrelin were measured at 0, 30, 60 and
120 min and appetite perceptions at 0, 30, 60, 90 and 120 min. A buffet-style test meal was presented at 120 min
to measure ad libitum EI. There was no correlation between the sample means for fasted salivary and plasma
ghrelin (r = 0.099, p = 0.637). Furthermore, there was no within-participant association between fasted salivary
and plasma ghrelin (r = -0.041, p = 0.725). Mean bias between fasted salivary and plasma ghrelin was -448 pg/
ml (95% confidence intervals (CI) = -623 - -273 pg/ml) and upper and lower limits of agreement (LOA) were 427
pg/ml and -1324 pg/ml, respectively. Variation in postprandial levels of salivary and plasma ghrelin withinparticipants
were not associated (r = -0.004, p = 0.943). There was no significant association between EI and
salivary (r = 0.003, p = 0.979) or plasma (r = -0.080, p = 0.492) ghrelin. Salivary ghrelin was not significantly
correlated with composite appetite score (r = 0.023; p = 0.654), though plasma ghrelin was (r = 0.225, p <
0.001). Mean bias between postprandial salivary and plasma ghrelin was -210 pg/ml (95% CI = -380 - -40 pg/
ml) and upper and lower LOA were 641 pg/ml and -1061 pg/ml, respectively. These findings suggest that
salivary and plasma ghrelin responses to drinks varying in protein content and quantity are unrelated and that
salivary ghrelin is not associated with EI or appetite perceptions in healthy non-obese adults. This trial was
registered at www.clinicaltrial.gov (NCT01597024).
Year
2021
Category
Refereed journal