Establishing the Glycaemic Index of Vegetable Smoothies (VEG-GI)

Study to Establish Glycaemic Response to the Ingestion of Vegetable Smoothies Expressed as Glycaemic Index Following Best Practice Guidelines

Glycaemic responses to carbohydrates ingested as fruit and vegetables may vary depending on factors inherent to the fruit or vegetable, and on the type of sugar. The aim of this project is to investigate the glycaemic responses to two new fruit and vegetable smoothies, and to establish the glycaemic index for each product relative to a glucose reference. Participants will undertake 4 postprandial tests with 2 different test drinks following best practice guidelines for glycaemic index testing. The test drinks (GREEN and RED) will be matched for carbohydrate to the glucose reference (CONTROL) which will be sampled two times. Fingerstick capillary blood sampling will measure glucose concentrations. These data will provide insight into how differing formulations can alter the glycaemic responses to fruit and vegetable drinks.

Study Overview

• Status: Completed
• Conditions: Glycaemic Index; Glycaemic Response; Glycaemic Response Measurements
• Intervention / Treatment: Other: Vegetable Smoothie

• Study Type: Interventional
• Enrollment (Actual): 16
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • Bath, United Kingdom, BA2 7AY
    • Department for Health, University of Bath

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Age: 18-65 years
• Body mass index 18-30 kg/m2

Exclusion Criteria:

• diagnosis of any form of diabetes
• intolerances or allergies to any of the study procedures (e.g. fructose/inulin intolerance)
• Fructose malabsorption
• Inborn errors of fructose metabolism (e.g. fructokinase deficiency, aldolase B deficiency, fructose-1,6-bisphosphatase deficiency)
• pregnant or lactating
• any condition that could introduce bias to the study (e.g. diagnoses of lipid disorders, including cardiovascular disease, or therapies that alter lipid or glucose metabolism, such as statins or niacin).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: CONTROL; 50 g glucose (55 g dextrose powder accounting for hydration) plus 519 mL water	Other: Vegetable Smoothie; Commercially available fruit and vegetable smoothie
Active Comparator: REPLICATE CONTROL; 50 g glucose (55 g dextrose powder accounting for hydration) plus 519 mL water	Other: Vegetable Smoothie; Commercially available fruit and vegetable smoothie
Experimental: RED; 500 mL of commercially available "Red Goodness" providing 50 g of carbohydrate [apple (47%), banana, chayote (8%), beetroot (7%), carrot (5%), cucumber (5%), cherry (3%), spinach (2%), mandarin, lemon, apple water, beetroot extract]. Plus 19 mL water to standardise volume	Other: Vegetable Smoothie; Commercially available fruit and vegetable smoothie
Experimental: GREEN; 519 mL of commercially available "Green Goodness" smoothie providing 50 g carbohydrate [apples (46%), banana, courgette (10%), chayote (8%), guava, cucumber (5%), lemon (3%), spinach (2%), mandarin, apple water spirulina extract, turmeric extract, mint extract].	Other: Vegetable Smoothie; Commercially available fruit and vegetable smoothie

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Glycaemic indices for 2 test drinks measured using capillary blood samples	Glycaemic indices [2-hour incremental area under the glucose curve (mmol/L-1x120 minutes) for each of the 2 test drinks relative to mean value of control conditions (CONTROL, REPLICATE CONTROL), expressed as a percentage] in capillary blood samples	120 minutes

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparisons between conditions in glucose concentration in capillary samples	Comparison of blood glucose concentration 2-hour incremental area under the curve (iAUC) min.mmol/L between test conditions	120 minutes
Comparisons between conditions in glucose concentration in capillary samples	Comparison of postprandial peak concentration mmol/L of blood glucose between test conditions (Cmax)	120 minutes
Comparisons between conditions in glucose concentration in capillary samples	Comparison of time to peak blood glucose concentration in minutes (Tmax) between test conditions	120 minutes
Comparisons between conditions in glucose concentration in capillary samples	Comparison of blood glucose concentration mmol/L at 2 hours between test conditions	120 minutes

Collaborators and Investigators

• Sponsor: University of Bath

Publications and helpful links

General Publications

• Brouns F, Bjorck I, Frayn KN, Gibbs AL, Lang V, Slama G, Wolever TM. Glycaemic index methodology. Nutr Res Rev. 2005 Jun;18(1):145-71. doi: 10.1079/NRR2005100.
• Gonzalez JT. Are all sugars equal? Role of the food source in physiological responses to sugars with an emphasis on fruit and fruit juice. Eur J Nutr. 2024 Aug;63(5):1435-1451. doi: 10.1007/s00394-024-03365-3. Epub 2024 Mar 16.

Study record dates

Study Major Dates

• Study Start (Actual): October 22, 2025
• Primary Completion (Actual): December 15, 2025
• Study Completion (Actual): December 15, 2025

Study Registration Dates

• First Submitted: July 22, 2026
• First Submitted That Met QC Criteria: July 22, 2026
• First Posted (Actual): July 27, 2026

Study Record Updates

• Last Update Posted (Actual): July 27, 2026
• Last Update Submitted That Met QC Criteria: July 22, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Glycaemic Index; Vegetable Smoothies
• Other Study ID Numbers: 10814-13276

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified data will be made available open access on the University of Bath Research Data Archive (RDA) at the point of publication in a peer-reviewed journal
• IPD Sharing Time Frame: These will become available at the point of publication permanently
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

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