This pilot study is being conducted to evaluate whether consumption of diet soda sweetened with sucralose and acesulfame-potassium leads to changes in the gut microbiota. Following a one week run-in period, healthy, young adults are randomized to consume either diet soda or carbonated water (control) three times per day for one week. Stool and urine samples are collected at baseline, following the run-in, and after the one-week intervention.

Inclusion Criteria:

• Healthy adults aged 18-35 years
• Consume less than 1 food/beverage with non-nutritive sweeteners per month
• Able and willing to consume diet soda three times daily for 1 week

Exclusion Criteria:

• Recent diet or significant weight change
• Antibiotic use in the past 3 months
• Diarrhea in the past two weeks
• Use of medications known to affect metabolism or weight
• Weight < 50 kg (110 lbs.)
• History of metabolic complications including high blood sugar, elevated cholesterol, or liver disease