## Sweet amplification : Effects of glucose intake on psycho-physiological responses to stress and relaxation

2022
Konstanz
Dissertation
Published
##### Abstract
Mental health problems are often linked to comorbidly occurring physical health impairments. For example, affective disorders such as depression are associated with an increased risk of metabolic disorders like obesity and type 2 diabetes, and vice versa. In this context, the dysregulation of important regulatory systems, e.g., the parasympathetic nervous system (PNS), the sympathetic nervous system (SNS), and the hypothalamic-pituitary-adrenal (HPA) axis, has been suggested as a possible link between mental and physical health. These systems are closely related to energy metabolism, and they may disrupt ongoing metabolic processes to enable the organisms to adapt to external demands. To date, we have an incomplete understanding of the crosstalk between energy metabolism and the PNS, SNS, and HPA axis. The aim of this thesis was to gain a deeper understanding of how metabolic factors influence the regulation of the PNS, SNS, and HPA axis, in humans. Using an experimental approach, I, together with my colleagues, specifically set out to study the influence of glucose intake (i.e., the consumption of a sweet and caloric drink) on the reactivity of the PNS, SNS, and the HPA axis to states of stress and relaxation. In a first step, and in the first project of this thesis (Chapter 2), we developed and successfully validated two standardized massage protocols for the induction of relaxation in the laboratory. These protocols will advance the systematic investigation of psychophysiological relaxation responses in humans in the future. In a second step, we used standardized stress and relaxation protocols to investigate the effect of sugar intake on the reactivity of the PNS, SNS, and HPA axis. The findings of the second project of this thesis (Chapter 3) revealed that glucose intake increased women’s HPA axis reactivity to psychosocial stress after an overnight fast. The results of the third project of this thesis (Chapter 4) showed an enhanced parasympathetic reactivity to slow paced breathing (SPB) after the consumption of a glucose-like (sweet and caloric) drink. While blood glucose concentrations were not significantly related to HPA axis reactivity to stress, they predicted higher PNS reactivity to relaxation. Neither subjective responses to stress, nor subjective responses to relaxation were altered by sugar intake. Taken together, the results of this thesis imply that sugar amplifies the reactivity of the PNS, SNS, and HPA axis in humans. The amplification could neither be explained by sugar’s sweet taste nor by its caloric content alone. Our results confirm the tight link be- tween energy metabolism and the PNS, SNS, and HPA axis and suggest that metabolic factors not only impact the basal activity of the systems but moreover their reactivity to external demands. Future studies will have to determine possible mechanisms behind this amplification and investigate its neural correlates and behavioral consequences. This knowledge will eventually contribute to a deeper understanding of the reasons why stress-related diseases are often comorbidly linked to metabolic disorders and may thereby advance the development of novel treatment complements.
150 Psychology
##### Keywords
stress, relaxation, cortisol, heart rate variability, autonomic nervous system, hypothalamus pituitary adrenal axis
##### Cite This
ISO 690MEIER, Maria, 2022. Sweet amplification : Effects of glucose intake on psycho-physiological responses to stress and relaxation [Dissertation]. Konstanz: University of Konstanz. Konstanz
BibTex
@phdthesis{Meier2022Sweet-59693,
year={2022},
title={Sweet amplification : Effects of glucose intake on psycho-physiological responses to stress and relaxation},
author={Meier, Maria},
school={Universität Konstanz}
}

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##### Examination date of dissertation
December 16, 2022
##### University note
Konstanz, Univ., Doctoral dissertation, 2022
Yes