Study Overview This research study, conducted by the Texas Christian University (TCU) Department of Nutritional Sciences and Kinesiology, aims to investigate the effects of carbonated prebiotic beverages (Olipop and Poppi) compared to caloric (Coca-Cola Original) and non-caloric (Diet Coke) beverages on satiety, blood glucose, insulin, and glucagon-like peptide-1 (GLP-1) responses in healthy male participants aged 18-40. The study is a single-blind, randomized crossover trial designed to explore how these beverages influence metabolic and appetite-related outcomes, addressing gaps in understanding the physiological impacts of functional beverages containing prebiotics versus widely consumed caloric and non-caloric alternatives.
Objectives and Hypotheses The primary objective is to evaluate the acute effects of four beverages-Olipop, Poppi, Diet Coke, and Coca-Cola Classic-on satiety, plasma glucose, insulin, and GLP-1 levels. Secondary objectives include assessing body composition and beverage palatability and gastrointestinal (GI) symptoms. The hypothesis is that prebiotic beverages will enhance satiety and GLP-1 secretion due to fiber content, potentially via gut microbiota fermentation, without significantly increasing glucose or insulin levels compared to Coca-Cola. Diet Coke may elicit a modest GLP-1 and satiety response due to artificial sweeteners, but minimal glucose/insulin changes. Coca-Cola is expected to cause significant glucose and insulin spikes due to its high sugar content. Additionally, hunger is expected to be reduced across all conditions, with prebiotic beverages potentially showing superior satiety effects.
Study Design
* Type: Prospective, interventional, single-blind, randomized crossover trial.
* Participants: 10 healthy males aged 18-40, accounting for a 30% attrition rate.
* Duration: Four visits, each 2-2.5 hours, separated by a one-week washout period (total \~10.5 hours).
* Randomization and Blinding: Each participant consumes all four beverages in random order, served in unlabeled black containers to minimize bias.
* Data Collection: Anthropometric measurements, body composition (DEXA scan), biochemical markers (glucose, insulin, GLP-1), and survey data (satiety, GI symptoms, beverage preference) are collected.
Study Procedures
1. Screening and Visit 1:
* Informed consent is obtained, followed by measurement of height, weight, and blood pressure.
* A finger-stick test assesses fasting blood glucose and HbA1c.
* Participants complete demographic, health, beverage preference, and 3-day food log questionnaires.
2. Visits 2-4:
* A DEXA scan measures body composition (visit 2 only).
* Participants fast for 8-12 hours before each visit.
* Blood pressure is measured, and fasting status is confirmed via finger-stick.
* An intravenous catheter is inserted for blood sampling at 0, 15, 30, 60, 90, and 120 minutes post-beverage consumption to measure glucose, insulin, and GLP-1.
* Participants consume one beverage (355 mL) within 5 minutes.
* Satiety Questionnaires are completed at baseline and specific intervals.
* GI Symptomps Questionnaire are filled out 24h after each visit.
* Beverage Rating QUesitonnaire will be applied at the end of each visit.
* Total blood volume per visit is approximately 30 mL.
Beverages Tested
* Olipop and Poppi: Prebiotic sodas containing inulin and other fibers, low calories (\~20-35 kcal).
* Diet Coke: Non-caloric, sweetened with aspartame (46 mg).
* Coca-Cola Original: Caloric (140 kcal, 39 g of sugar).
Recruitment and Screening
* Methods: Flyers, emails, social media, and in-person recruitment in TCU classes.
* Process: Potential participants complete an online screening form by following the QR code from the flyers and emails. Eligible candidates undergo phone screening to confirm inclusion/exclusion criteria and receive a study overview.
Data Collection and Analysis
\- Anthropometric, body composition, biochemical, and survey data will be collected as indicated in Outcome Measures.
Risks and Mitigation
1. Blood Draw/IV Catheter: Low risk of discomfort, bruising, or infection; mitigated by trained personnel and sterile techniques.
2. DEXA Scan: Minimal radiation exposure (\~0.1 mSv, equivalent to background radiation); limited to one scan.
3. Data Breach: Risk minimized by deidentification, secure storage, and restricted access to IRB-approved personnel.
4. GI Discomfort: Possible with prebiotic beverages; monitored via GI Symptoms Questionnaire.
Benefits
* Direct: Participants receive a $150 gift card, DEXA scan results, baseline glucose, and HbA1c levels (finger sticks)
* Indirect: No direct benefits, but results may inform evidence-based recommendations for beverage consumption.
Results Sharing
* Baseline finger-stick results (glucose, HbA1c, lipids) are shared at testing.
* Lab-measured glucose and insulin levels, analyzed in batches after all participants complete the study, will not be shared, as delayed analysis limits immediate clinical utility.
