SweetSpot - The Effect of Non-nutritive Sweeteners on Health

SweetSpot - The Effect of Non-nutritive Sweeteners on Glucose Regulation, Gut Microbiome, and Gut Hormone Secretion in Healthy Adults: a Fully Controlled Cross-over Intervention Study

The aim of the study is to investigate the effect of non-nutritive sweeteners on glucose regulation. Secondary objectives are to investigate the effect of NNS on gut microbiome, gut hormone secretion, sweet taste sensitivity and preference, and the excretion of NNS in urine.

Study Overview

• Status: Recruiting
• Conditions: Healthy Adult
• Intervention / Treatment: Other: Diet with non-nutritive sweeteners; Other: Diet without non-nutritive sweeteners

Detailed Description

Sugar intake has increased over the years, simultaneously with the prevalence of overweight and obesity. To decrease sugar intake, consumption of non-nutritive sweeteners (NNS) has increased and opinions on its use remain divided. A fully controlled dietary intervention using a NNS mixture and dose that is similar to real-life intake, is therefore necessary to advance our understanding of the potential effects of NNS on glucose regulation, gut microbiome, and gut hormone secretion under real-life conditions.

The aim of this study is to investigate the effect of non-nutritive sweeteners on glucose regulation. Secondary objectives are to investigate the effect of NNS on gut microbiome, gut hormone secretion, sweet taste sensitivity and preference, and the excretion of NNS in urine.

To do this, a single blind, fully controlled dietary intervention with a cross-over design will be performed. The study will consist of 2x8 weeks of intervention, with a washout of > 6 weeks in between. The study population will be 60 healthy adults aged 45-79, with a BMI between 20-35 kg/m2.

The study will consist of a fully controlled diet of two 8-week intervention periods (2 weeks run-in + 6 weeks intervention). The diets differ in the presence of non-nutritive sweeteners (NNS): NNS-diet versus non-NNS diet, where additional NNS are added to the NNS-diet.

The primary outcome measure will be the within person difference in blood glucose incremental area under the curve following a 75 g glucose tolerance test between the NNS diet and the non-NNS diet. Secondary outcome measures are the effect of NNS on Matsuda index, insulin response, blood lipid profile, and gut hormone secretion will be determined. The effect of NNS on small- and large intestinal microbiome will be investigated by a change in composition, functionality, and short chain fatty acid content. The effect of NNS on sweet taste sensitivity, preference, and liking will be investigated, as well as the excretion of NNS in urine and saliva.

The total time invested by participants is around 85 hours. Participants are restricted for 16 weeks in their eating habits, since they follow a fully controlled diet prepared by the research facility. Participants will visit the research facility in total 38 times. In total, ~ 603 mL of blood will be drawn by experienced nurses over the entire RCT (>6 month period). During DEXA scans, participants will receive a total of about 0.006 mSv of radiation.

Invasive measurements that participants can experience as burden are collection of faecal and urine samples, and finding back the Simba capsules in the stool. Non-invasive measurements for participants are wearing the CGM, wearing the ActiGraph, consuming the blue cakes, and performing sensory tests.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Netherlands
  • Gelderland
    • Wageningen, Gelderland, Netherlands, 6708WG
      • Recruiting
      • Wageningen University & Research
      • Contact: Diederik Esser, Dr.; Phone Number: +31317480084; Email: sweetspot@wur.nl

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age 45-79 years;
• BMI of 20-35 kg/m2;
• Having veins suitable for placement of a venflon catheter.

Exclusion Criteria:

• Diseases or prior surgeries affecting the stomach, liver, kidneys or intestines (allowed i.e. appendectomy);
• Cardiovascular diseases (e.g. heart failure) or cancer (e.g. non-invasive skin cancer allowed);
• Diagnosed with type 1 or type 2 diabetes;
• Drug treated thyroid diseases (well substituted hypothyroidism is allowed for inclusion);
• HbA1c level >6.5% (>48 mmol/mol), as measured during the screening visit;
• Anaemia defined as Hb concentrations <8.5 mmol/L for men and <7.5 mmol/L for women via finger prick;
• Regular use of/receiving medication interfering with research outcomes (as judged by research physician), such as use of glucose lowering drugs, insulin, or use of medication that impacts the gastro-intestinal system;
• Use of antibiotics over the last 3 months before study start;
• Donated blood within 2 months prior to the screening;
• Food allergies, intolerances (including lactose/gluten intolerance) for products used in the study design and/or dietary restrictions interfering with the study (including special diets and eating disorders);
• Followed a diet that can interfere with the study outcomes within 1 month prior to the screening (e.g. ketogenic, sugar free, carbohydrate free);
• Not willing to eat all products in the study diet, including eggs and dairy. Vegetarian is possible;
• Not willing to consume non-nutritive sweeteners;
• Not willing to quit the use of supplements that can interfere with the study outcomes (e.g. pre- or probiotics).
• Intention to change the intensity of exercise during the study period or planning to join a intensive sport event (e.g. marathon or triathlon);
• Intention to lose or gain weight;
• Working night shifts regularly;
• Smoking regularly
• Use of soft and/or hard drugs (cannabis included);
• Abuse of alcohol (defined as >14 glasses (women) or >21 glasses (men) of alcoholic beverages per week);
• Being pregnant or lactating or planning to become pregnant;
• Inability to understand study information and/or communicate with staff;
• Participation in another study that involves an intervention within two months prior to the intervention;
• Working or doing a thesis/internship at the division of Human Nutrition & Health, or the Food, Health & Consumer Research group of Wageningen Food & Biobased Research.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: NNS / no-NNS; In this arm, participants will first receive the NNS diet, and the no-NNS diet in the second study period.	Other: Diet with non-nutritive sweeteners; Fully controlled diet with added mixture of non-nutritive sweeteners. The mixture consist of 6 different non-nutritive sweeteners: acesulfame-K, aspartame, cyclamate, saccharin, sucralose, and rebaudioside A (stevia).; Other: Diet without non-nutritive sweeteners; Fully controlled diet without any non-nutritive sweeteners added.
Other: No-NNS / NNS; In this arm, participants will first receive the no-NNS diet, and the NNS diet in the second study period.	Other: Diet with non-nutritive sweeteners; Fully controlled diet with added mixture of non-nutritive sweeteners. The mixture consist of 6 different non-nutritive sweeteners: acesulfame-K, aspartame, cyclamate, saccharin, sucralose, and rebaudioside A (stevia).; Other: Diet without non-nutritive sweeteners; Fully controlled diet without any non-nutritive sweeteners added.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in change in 2h iAUC glucose after 6 weeks between the intervention and the control.	The primary outcome measure is the difference in change in iAUC of blood glucose levels following a 2-hour oral glucose tolerance test (OGTT) after six weeks between the intervention period and the control period.	Week 2 and week 8 in both intervention periods (4 times in total)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Matsuda index	Matsuda index after an OGTT	Week 2 and week 8 in both intervention periods (4 times in total)
Fasting blood glucose	Fasting blood glucose	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.
Fasting blood insulin	Fasting blood insulin	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.
Postprandial insulin response	2-hour iAUC blood insulin during OGTT	Week 2 and 8 in both intervention periods (4 times in total).
Postprandial glucose response after a breakfast	Postprandial blood glucose responses (PPGR) following specific meals measured by CGM.	Week 7 in both study periods (2 times in total)
Blood lipid profile	All circulating blood lipids, including all cholesterol types, triglycerides, and free fatty acids (FFAs).	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.
Gut microbiota composition	Microbiota composition in faeces	Average of three samples per timepoint. Measured at baseline & 2 times per intervention period (week 2 and week 8). 15 samples over 5 timepoints in total.
Gut microbiota function	Microbiota functionality measured in faeces	Average of three samples per timepoint. Measured at baseline & 2 times per intervention period (week 2 and week 8). 15 samples over 5 timepoints in total.
Microbial metabolites	Microbial metabolites measured in faeces	Average of three samples per timepoint. Measured at baseline & 2 times per intervention period (week 2 and week 8). 15 samples over 5 timepoints in total.
Small intestinal microbiota composition	Microbiota composition of the small intestine measured with Simba Capsules	Week 7 of both intervention periods (2 times in total).
Gastro-intestinal transit time	Gastro-intestinal transit time measured with blue muffins.	Baseline & week 7 of both intervention periods (3 times in total).
Oral microbiome composition & function	Oral microbiome composition & function measured in saliva	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.
Postprandial GLP-1 secretion	3-hour AUC of GLP-1 during an OGTT.	Week 2 and 8 of both intervention periods (4 times in total).
Postprandial GIP secretion	3-hour AUC of GIP during an OGTT.	Week 2 and 8 of both intervention periods (4 times in total).
Sweetness-liker phenotype	Sweetness-liker phenotype, with the sweetness liker test.	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.
Excretion of NNS in urine	Excretion of NNS in urine	Baseline, week 2 and week 8 in intervention period 1, and every two weeks in intervention period 2 (7 times in total).
Excretion of NNS in saliva	Excretion of NNS in saliva	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.
Sweetness preference & liking	Sweetness preference & liking measured on a rank-rating scale. Preference will be determined using the categorical values from the rank-rating scale (1-5), and liking will be determined using the continuous values from the rank-rating scale (0-100).	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.
Sweet taste sensitivity	Sweet taste sensitivity measured on a 100mm Visual Analogue Scale. A higher score for all solutions indicates a higher sweet taste sensitivity.	Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Body composition	Body composition as measured by DEXA (Dual Energy X-ray Absorptiometry).	Baseline & week 8 of both intervention periods (3 times in total).
Habitual food intake	Habitual dietary intake assessment with a food frequency questionnaire (FFQ).	Baseline
Physical activity level	Physical activity level by the Short Questionnaire to Assess Health-enhancing physical activity (SQUASH).	Baseline.
Habitual NNS consumption	Habitual NNS consumption by questionnaire	Baseline
Genetic variation	Single Nucleotide Polymorphisms (SNPs) in genes relevant collected using buffycoat.	Baseline
Anthropometrics	Measured as weight (kg), height (m), waist circumference (cm), and hip circumference (cm). Weight and height will be combined to report BMI in kg/m^2.	Baseline
Gastro-intestinal symptoms	Gastro-intestinal symptoms by GSRS questionnaire.	Once during the characterisation period (1 week), and every week during the first intervention period (8 weeks) and every week during the second intervention period (8 weeks). In total up to 17 weeks.
Satiety	Satiety questionnaire, adapted from the Control of Eating Questionnaire.	Once during the characterisation period (1 week), and every week during the first intervention period (8 weeks) and every week during the second intervention period (8 weeks). In total up to 17 weeks.
Taste function	Measure the ability to recognize the basic tastes in different concentrations, assessed with validated Taste Strips.	Baseline

Collaborators and Investigators

• Sponsor: Wageningen University
• Collaborators: Symrise AG; Tate & Lyle; TKI Agri & Food; American Beverage Association; Food & Biobased Research - Wageningen UR; The Magnum Ice Cream Company; Yildiz Holding

Study record dates

Study Major Dates

• Study Start (Actual): February 23, 2026
• Primary Completion (Estimated): November 26, 2026
• Study Completion (Estimated): November 26, 2026

Study Registration Dates

• First Submitted: January 13, 2026
• First Submitted That Met QC Criteria: January 13, 2026
• First Posted (Actual): January 23, 2026

Study Record Updates

• Last Update Posted (Actual): February 27, 2026
• Last Update Submitted That Met QC Criteria: February 24, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: gut microbiome; glucose metabolism; gut hormones; non-nutritive sweeteners
• Additional Relevant MeSH Terms: Chemical Actions and Uses; Food; Diet, Food, and Nutrition; Physiological Phenomena; Food and Beverages; Nutritional Physiological Phenomena; Specialty Uses of Chemicals; Food Additives; Food Ingredients; Flavoring Agents; Sweetening Agents; Diet; Non-Nutritive Sweeteners
• Other Study ID Numbers: NL010297

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No