SweetSpot - The Effect of Non-nutritive Sweeteners on Health

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.

• Matsuda index [Time frame: Week 2 and week 8 in both intervention periods (4 times in total)]
• Fasting blood glucose [Time frame: Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.]
• Fasting blood insulin [Time frame: Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.]
• Postprandial insulin response [Time frame: Week 2 and 8 in both intervention periods (4 times in total).]
• Postprandial glucose response after a breakfast [Time frame: Week 7 in both study periods (2 times in total)]
• Blood lipid profile [Time frame: Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.]
• Gut microbiota composition [Time frame: 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 [Time frame: 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 [Time frame: 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 [Time frame: Week 7 of both intervention periods (2 times in total).]
• Gastro-intestinal transit time [Time frame: Baseline & week 7 of both intervention periods (3 times in total).]
• Oral microbiome composition & function [Time frame: Baseline & 2 times per intervention period (week 2 and week 8). 5 times in total.]