Brain and Glycemic Responses to Sweet Soft Drinks

Overview

The goal of this observational study is to determine changes in brain activity and blood sugar in response to the ingestion of flavored waters sweetened with either the nutritive sugar sucrose or different low-caloric sweeteners in healthy normal-weight individuals aged between 18 and 30 years. The main question it aims to answer is in how far brain and glycemic responses differ between a sugar-sweetened drink and drinks sweetened with different low-caloric sweeteners. Participants will visit after an overnight fast six times and then have an MRI brain scan before and after consumption of 500 ml of one of the study drinks (beverage sweetened with sucrose or one of four non-caloric sweeteners, or water).

Rationale: The brain is crucial in the regulation of energy intake and maintaining homeostasis which is subserved by an interaction of homeostatic and reward-related brain areas. These brain areas integrate multiple neural and hormonal signals related to energy content such as sweet taste and food reward in the form of ingested energy. Sugar-sweetened soft drinks have been shown to contribute to overconsumption and obesity. Therefore, there is great consumer interest in drinks with low-caloric sweeteners because they do not contribute to energy intake while still providing the hedonic experience of sweet taste. However, different low-caloric sweeteners may have differential effects on the brain because of (subliminal) taste difference and their different metabolic fate. We hypothesize that the brain and glycemic responses to drinks sweetened with sugar and different low-caloric sweeteners will be different. This may have implications for their reward value. Objective: To determine changes in brain activity in response to the ingestion of flavored waters sweetened with either the nutritive sugar sucrose or different low-caloric sweeteners. Study design: Randomized crossover design with six treatments. Study population: 30 healthy, non-smoking, normal-weight individuals, aged between 18 and 30 years. Intervention: Participants will be scanned using MRI before and after consumption of six 500-ml drinks: water; water + sucrose; water + sucralose; water + stevia extract; water + allulose + stevia; water + monk fruit extract. Regional cerebral blood flow (rCBF) and resting state functional MRI (rsfMRI) scans will be made at baseline and at t=5 and t=30 min. Additionally, gastric emptying of the drinks will be examined through gastric MRI at t=15, 25 and 45 min. Blood samples will be collected to measure changes in insulin and glucose levels at baseline and at t=5, 15, 30, 45 and 60 min for all sweet treatments. Participants will rate their appetite and thirst at baseline and at t=15, 25, 30, 45 and 60 min.