Assessment of Glycemic Index for Dried Saskatoon Berries and Powder in Healthy Subjects

The glycemic index (GI) ranks carbohydrate-containing foods based on their effect on postprandial blood glucose levels. Foods or food products with lower GI values (55 or less) are absorbed more slowly, gradually increasing blood glucose and insulin levels. Fruits are believed to have a lower GI, making them potentially beneficial for individuals seeking to manage blood sugar levels. Previous studies from our and other groups suggest that Saskatoon berry (SB) is a potential functional food for glucose management. The glycemic index (GI) of dried SB powder and whole fruit remains undetermined, limiting our ability to make precise dietary recommendations. This study aims to evaluate the GI in both whole fruit and powder forms of SB. The determination of GI on SB products allows us to provide evidence-based guidance for healthcare providers when recommending SB as a functional food for glucose control.

Study Overview

• Status: Completed
• Conditions: Healthy Volunteers (HV)
• Intervention / Treatment: Dietary supplement: Saskatoon berry powder

Detailed Description

I. Research Objective: This study aims to evaluate the GI of Saskatoon berry powder and whole fruit in healthy individuals.

II. Methodology:

Study Design

• Type: Randomized, open-label study.
• Duration: Approximately 4 weeks for each participant.
• Setting: Clinical nutrition laboratory.

Participant Recruitment:

Following approval from the University of Manitoba Research Ethics Board, we will distribute recruitment materials across the university campus. Interested individuals may contact the research coordinator to express interest in participation.

Target enrollment: 10-20 participants

Eligibility Requirements:

• Individuals in good health (males and females)
• Between 18 and 74 years of age
• Body Mass Index (BMI) within the range of 18.5-29.9 kg/m²
• Free from diabetes, hyperlipidemia, and hypertension
• Must not be taking medications for diabetes, cholesterol, or blood pressure management.

Required Resources

• Saskatoon berry powder (Prairie Berry Inc.)
• Whole Saskatoon berries (Prairie Berry Inc.)
• Control substance: 25g glucose drink
• Glucose monitoring instruments
• Water (250ml) for powder administration Protocol Overview Visit #1: Initial Session: Research consent The research coordinator will conduct informed consent procedures at an agreed-upon location.

• Initial Assessment:

  • Blood pressure measurement
  • Heart rate monitoring
  • Anthropometric measurements Visit #2: Primary Testing Session

• Preparation Guidelines:

  • Fasting period: 10-14 hours overnight
  • Session start: 9:00 AM
• Testing Protocol:

The participant will receive either Saskatoon berry powder (25g carbohydrate equivalent) with 250ml of water (consumption within 10 minutes), or whole Saskatoon berries (25g carbohydrate equivalent, consumption within 20 minutes) or glucose drink (25 g carbohydrate, consumption with in 10 min).

Blood glucose monitoring schedule:

Initial reading (0 min) 15 minutes post-consumption 30 minutes post-consumption 45 minutes post-consumption 60 minutes post-consumption 90 minutes post-consumption 120 minutes post-consumption Visit #3: Reference Food Assessment Participants will undergo an identical protocol with oral glucose drink (25g carbohydrate equivalent) 2-7 days following the initial assessment.

Important: A minimum 48-hour washout period is required between each test (control or berry preparation).

Analytical Methods The glycemic index will be determined through analysis of blood glucose area under curve (AUC), following established protocols (Brouns et al., 2005).

• GI will be calculated as the ratio of the incremental AUC (iAUC) for SB to the iAUC for glucose drink, multiplied by 100.
• Data will be presented as mean ± standard deviation.
• Paired t-tests or equivalent non-parametric tests will be used to compare iAUC between SB and glucose drink.
• A p-value < 0.05 will be considered statistically significant.

• Study Type: Interventional
• Enrollment (Actual): 10
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Manitoba
    • Winnipeg, Manitoba, Canada, R3E 3P4
      • University of Manitoba

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Individuals in good health (males and females)
• Between 18 and 74 years of age
• Signed informed consent

Exclusion Criteria:

• Body Mass Index (BMI) >= 30 kg/m²
• Diabetes, hyperlipidemia, and hypertension
• Taking medications for diabetes, cholesterol, or blood pressure

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: SB powder; Volunteers drink 25 g of SB powder (25g carbohydrate equivalent) with 250ml water (consumption within 10 minutes)	Dietary supplement: Saskatoon berry powder; After oral intake of SB powder, dried whole SB fruit or glucose drink, finger tip blood glucose will be measured 15, 30, 45, 60, 90 and 120 minutes after the consumption.; Other Names: Dried whole Saskatoon berry; Glucose drink as control
Experimental: Dried whole SB fruit; Volunteers intake Dried whole SB fruit (25g carbohydrate equivalent) within 20 minutes. Participants have option to choose intake one or both SB products. One week interval is required between the interventions.	Dietary supplement: Saskatoon berry powder; After oral intake of SB powder, dried whole SB fruit or glucose drink, finger tip blood glucose will be measured 15, 30, 45, 60, 90 and 120 minutes after the consumption.; Other Names: Dried whole Saskatoon berry; Glucose drink as control

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Glycemic index	Glyemic index after the consumption of SB powder or dried whole SB compared to glucose drink	15-120 minutes after consumption dietary supplement

Collaborators and Investigators

• Sponsor: University of Manitoba

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.
• Zhao R, Khafipour E, Sepehri S, Huang F, Beta T, Shen GX. Impact of Saskatoon berry powder on insulin resistance and relationship with intestinal microbiota in high fat-high sucrose diet-induced obese mice. J Nutr Biochem. 2019 Jul;69:130-138. doi: 10.1016/j.jnutbio.2019.03.023. Epub 2019 Apr 9.

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2025
• Primary Completion (Actual): November 20, 2025
• Study Completion (Actual): November 20, 2025

Study Registration Dates

• First Submitted: March 31, 2025
• First Submitted That Met QC Criteria: April 7, 2025
• First Posted (Actual): April 15, 2025

Study Record Updates

• Last Update Posted (Actual): January 8, 2026
• Last Update Submitted That Met QC Criteria: January 6, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: blood glucose; Glycemic index; Postprandial glucose
• Other Study ID Numbers: HS26810 (B2025:012)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No