Non-nutritive sweeteners are used as a substitute for simple sugars to improve the palatability of food products without increasing their sugar and calorie content. They represent a global market of 7 billion euros, with an annual growth of 5%. Reducing their consumption therefore seems to be excluded. Some studies have focused on the impacts of these substances on brain activity. According to a recent study, continuous consumption of low doses of saccharin in adult mice significantly decreases the level of dopamine in the prefrontal cortex and significantly increases striatal dopamine, which modifies decision-making strategies. Resting-state functional Magnetic Resonance Imaging (r-fMRI) studies in humans have also shown that an increase in striatal dopaminergic activity modifies the resting-state functional connectivity of brain regions linked to the reward circuit. r-fMRI allows the characterization of brain networks and the strength of correlations between brain regions, without any specific task being required. It is a rapid, non-invasive technique that can measure changes in brain functional connectivity.
In addition to r-fMRI, diffusion tensor imaging (DTI) is able to assess white matter microstructure and the integrity or otherwise of fiber tracts. Several parameters such as the fractional anisotropy (FA), coefficient of white matter, mean diffusivity, and radial diffusivity can be modified in the event of changes in functional connectivity, reflecting axonal rearrangements, not visible on conventional MRI sequences. Based on previous research, investigators hypothesize that (1) chronic consumption of non-nutritive artificial sweeteners increases striatal dopaminergic activity. (2) This modification is accompanied by changes in resting-state functional connectivity in brain regions of interest associated with the reward circuit in healthy young adults.
Then, the primary objective of this study is to compare, in the resting state, the differences in functional connectivity of brain regions of interest between "non/low consumers" and "high consumers" of sweeteners at the start of the study using r-fMRI.
The key secondary objective of this study is to assess changes in brain connectivity using r-fMRI in non- and low-consuming subjects before and after a transient increase in their sweetener consumption over 5 weeks.
The secondary objectives include assessing daily sugar consumption (5-week follow-up), daily consumption of non-energy-rich artificial sweeteners (5-week follow-up), Body Mass Index (BMI), physical activity level, and white matter microstructure and fibrous tract integrity using a diffusion-weighted MRI (DTI) sequence.
Men and women aged 18 to 30 (and in good health)
Having low or no sweetener consumption (~8 mg ± 5.05 mg/day) or high consumption (~80 mg ± 91.72 mg/day)
Having a BMI of 18.5 < 24.9
For young women: having effective contraception maintained throughout the study
Refusing to participate in the research
With impaired understanding, according to the investigator
Volunteer under guardianship/curatorship/deprived of liberty or under legal protection
Incompatibility of healthy volunteers with the medical imaging center's safety criteria for conducting 3 Tesla MRI experiments