# Effect of sweet and caloric drinks on cardiac reactivity to slow-paced breathing in healthy adults

## TL;DR

This study examines how sweet and caloric drinks affect heart responses during slow-paced breathing in healthy adults.

## Contribution

The study reveals how hyperglycemia influences autonomic cardiac reactivity during a relaxing exercise.

## Key findings

- Hyperglycemia triggered parasympathetic withdrawal and sympathetic activation.
- Slow-paced breathing increased parasympathetic activity and subjective relaxation across all groups.
- Results support the autonomic space model and the link between autonomic regulation and blood glucose.

## Abstract

Cardiac reactivity is proposed to be a central indicator of autonomic functioning. While hyperglycemia plays a limited role in cardiac stress reactivity, it is unclear whether it may modulate cardiac reactivity in non-stressful situations. We investigated the effect of glucose on cardiac reactivity to a relaxing exercise, namely, slow-paced breathing (SPB). A total of 115 adults (age mean = 23.28 years, SD = 6.88; 76% female) either consumed a sweet & caloric, a sweet, a caloric drink, or pure water after baseline. Later, they performed a sustained attention test and SPB. Electrocardiography and impedance cardiography was obtained, and blood glucose and subjective relaxation were measured repeatedly. We analyzed changes in parasympathetic (root mean square of successive differences [RMSSD]) and sympathetic (pre-ejection period [PEP]) cardiac activity and subjective relaxation using growth curve models and performed correlational analyses. Hyperglycemia triggered cardiac PNS withdrawal and SNS activation. Despite this, SPB increased cardiac PNS activity and subjective relaxation and decreased cardiac SNS activity in all groups. Our results align with the autonomic space model and highlight the tight link between autonomic regulation and blood glucose homeostasis. Hyperglycemia might play a limited modulating role in cardiac reactivity to slow-paced breathing.

The online version contains supplementary material available at 10.1038/s41598-025-00980-w.