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
Parallel
administration of questionnaires
Other interventionDuring this visit, the investigator will again explain the study objectives and procedure. Once these explanations have been provided, healthy volunteers will be able to give their informed consent to participate. After signing the consent form, the following will be conducted during this visit: * A medical examination. * An electronic questionnaire including two consumption frequency assessment tools, adapted in French, to measure daily sugar and artificial sweetener intake. * Five tests assess the level of dependence on alcohol, drugs (cannabis, solvents, tranquilizers, barbiturates, cocaine, stimulants, hallucinogens, or narcotics), gambling, video games, and possible eating disorders. Volunteers with a score deemed above the norm for at least one of these six tests will be excluded from this study. * A urine screening test for drug use (cannabis, opiates, amphetamines, cannabinoids, benzodiazepines, cocaine) will be performed during this visit.
carrying out a MRI scan
Other interventionA functional exploration using resting-state fMRI and microstructural tissue organization using DTI will take place in the days following the inclusion visit, depending on the availability of "research" slots in the Department of Radiology and Imaging, Clermont-Ferrand University Hospital.
Can distribution visit for subjects in the "non/low" sweetener consumption group
Dietary supplementDuring this visit, scheduled following the MRI, subjects will go to the PIC/CIC where they will be given cans for the 5 weeks of the nutritional intervention (660 ml of sweetened beverage, or 2 cans per day). Subjects will be advised to arrive by car if possible and to park in the PIC/CIC parking lot at the foot of the building. Drinks will be provided to the subject in one or two batches (with an additional visit to the center to pick up any missing drinks) at the subject's convenience. They will also receive instructions for completing the electronic questionnaire to assess daily sugar and sweetener consumption. Subjects will complete this questionnaire weekly, which they will receive by email. Their email address will be collected during this visit.
carrying out a MRI scan
Other interventionA functional exploration using resting-state fMRI and microstructural tissue organization using DTI, post-nutritional intervention (5 weeks) in non- and low-sugar consumers: this exploration will take place depending on the availability of "research" slots at the Department of Radiology and Imaging, Clermont-Ferrand University Hospital.
1. At rest, functional connectivity between brain areas in healthy subjects, non/low consumers and high consumers of sweetener
Resting-state functional magnetic resonance imaging (rs-fMRI) is a method that studies the connectivity of different regions of the nervous system. Based on the acquisition of the BOLD (Bond Oxygen Level Dependent) signal, this method focuses more specifically on the study of low-frequency fluctuations (\<0.1 Hz) of this signal. The goal of resting-state imaging is to identify the synchronous activation of different regions of the brain and brainstem, in the absence of a stimulus or a task being performed. This activation can be observed between physically connected regions, or not, and demonstrates the involvement of these regions in a common network called the "Resting State Network" (RSN), which brings together different brain regions involved in common functions; this is referred to as "functional connectivity" between these regions. Areas of interest involved in the reward circuit (amygdala, nucleus accumbens, anterior insula, striatum, the prefrontal cortex, hypothalamus).
Functional connectivity, at rest, before and after nutritional intervention in non- and low-sugar consumers (criterion for the key secondary objective).
rs-fMRI
The amount of sugar consumed per day during the 5 weeks of nutritional intervention in non- and low-sugar consumers (mg/day).
Non-Nutritive Sweetener Food Frequency Questionnaire
The amount of artificial sweeteners consumed per day during the 5 weeks of nutritional intervention in non- and low-sugar consumers. (mg/day).
Non-Nutritive Sweetener Food Frequency Questionnaire
Body Mass Index (BMI)
Body mass index (BMI) is a medical screening tool that measures the ratio of your height to your weight to estimate the amount of body fat you have. Healthcare providers calculate BMI by using weight in kilograms (kg) divided by the square of height in meters (m2). Healthy BMI range: 18.5 - 24.9
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