Effects of sugar and sweetener on the acute endocrine stress response in fasted women
The endocrine stress response helps to maintain homeostasis at times of increased demand and supports survival through energy mobilization. Paradoxically, low blood glucose levels impede the endocrine stress response, yet increasing blood glucose levels through sugar consumption prior to stress restores it. This suggests that glucose availability may play a causal role in the endocrine stress response. However, sugar has other distinct properties beyond the raise of blood glucose concentration. Here, we investigated the potential role of sweetness in restoring the cortisol stress reactivity after fasting. N=152 women (mean(age)=21.53, sd(age)=2.61) participated in a psychosocial stress test for groups in the morning after an overnight fast. Prior to stress induction, participants either consumed a drink that contained a caloric sweetener (sugar, n=51), an equally sweet drink containing non-caloric sweetener (sweetener, n=46), or water (n=56). Salivary cortisol and blood glucose levels were assessed repeatedly. Former studies suggested that sugar load prior to stress leads to increased cortisol responses compared to water, and sweetener. The effects of the consumed drinks on cortisol trajectories were tested using multilevel mixed models. Unexpectedly, we found that sugar and sweetener each significantly increased cortisol stress reactivity compared to water. Indeed, sweetener lead to cortisol increases comparable to sugar. Changes in blood glucose levels after drink consumption were not significantly associated with stress-induced increases in cortisol. This suggests that not the metabolic properties of sugar, but properties of sweet taste prior to stress are critical to boost the endocrine stress response to stress.