Metabolic Benefits of Drinking Blueberry Tea in Type 2 Diabetes

Plant derived compounds, e.g. flavonoids from dark chocolate, green tea, or blueberries, show great potential as nutraceuticals for the treatment of various diseases such as type 2 diabetes (T2D). Flavonoids have been suggested to improve glucose metabolism, reduce blood lipids, reduce oxidative stress and improve vascular function. For these reasons we recently investigated the effects of daily consumption of locally produced blueberry tea and demonstrated that this could partially restore insulin sensitivity in an animal model. We propose to translate these findings to assess the efficacy of this nutraceutical as a new treatment for improving glucose tolerance in people with T2D.

Study Overview

• Status: Recruiting
• Conditions: Type 2 Diabetes
• Intervention / Treatment: Other: Blueberry Tea

Detailed Description

Current treatments for T2D are limited, have unwanted side effects, and lose effectiveness over time. There is a growing public interest in the use of complementary and alternative approaches for treating insulin resistance and T2D. Blueberries, blueberry leaves and cinnamon have each been reported to improve insulin sensitivity or insulin action. Blueberry Boost™ is a locally produced Blueberry Tea and is a proprietary blend of dried blueberries (37% wt/wt), blueberry leaves, raspberry leaves, spearmint leaves and cinnamon.

It is well established that improving glycemic control is important for managing insulin resistance and T2D and the associated vascular pathologies that directly contribute to end-organ damage (microvascular disease), hypertension and cardiovascular disease (stroke, heart attack and heart failure). We have recently demonstrated that a unique blueberry tea blend fully restores the vascular insulin sensitivity in muscle of the high-fat fed insulin-resistant rat model and is associated with substantial improvements in muscle glucose uptake and whole body insulin sensitivity. We propose to translate these findings to assess the efficacy of this nutraceutical as a new treatment for improving glucose tolerance in people with T2D.

Aim: Determine whether chronic consumption (4 weeks) of blueberry tea can improve metabolic and vascular health in people with and without T2D.

• Study Type: Interventional
• Enrollment (Anticipated): 36
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Michelle A Keske, PhD; Phone Number: +61 3 6226 2669; Email: Michelle.Keske@deakin.edu.au

Study Locations

• Australia
  • Tasmania
    • Hobart, Tasmania, Australia, 7000
      • Recruiting
      • Menzies Institute for Medical Research
      • Contact: Michelle A Keske, PhD; Phone Number: +61 3 6226 2669; Email: Michelle.Keske@deakin.edu.au
      • Contact: Keske

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 75 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Aged 18-75 years.
• Normal to overweight (BMI 19-35 kg/m2).
• On lifestyle or metformin only diabetes treatment.
• Normotensive (seated brachial blood pressure <160/100 mmHg).
• No history of T2D (e.g. fasting plasma glucose <7.0mM); or with clinically diagnosed T2D on metformin or lifestyle intervention only (e.g. fasting plasma glucose ≥7.0mM, HbA1c).
• Willing to drink blueberry tea for 4 weeks (3 times per day with meals).

Exclusion Criteria:

• Age <18 yrs or >76 yrs
• Morbidly obese with a BMI ≥36 kg/m2
• Not on lifestyle and/or metformin only treatment for diabetes (e.g. insulin injections, sulphonylureas).
• History of myocardial infarction or stroke
• History of malignancy within past 5 years (except for non-melanoma skin cancers)
• Current smoker
• History of severe liver disease
• History of drug or alcohol abuse
• Elective major surgery during the course of the study
• Pregnancy/lactation
• Currently consuming (or have regularly consumed in the past 2 months) blueberry tea, or supplements containing blueberries, blueberry leaves, raspberry leaves, spearmint or cinnamon.
• Participation or intention to participate in another clinical research study during the study period.
• Not willing to consume blueberry tea for 4 weeks.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Blueberry Tea; 3 cups of blueberry tea per day x 4 weeks	Other: Blueberry Tea; Blueberry Tea
No Intervention: No Treatment

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Improvement in Glucose Tolerance after 4 weeks of drinking blueberry tea.	Oral glucose tolerance test (75g glucose) measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design). Blood glucose and plasma insulin levels measured at 0, 15, 30, 60, 90 and 120 min following consumption of glucose load.	4 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Improvement in Hemoglobin A1c (HbA1c) levels after 4 weeks of drinking blueberry tea.	HbA1c levels measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks.
Improvement in fasting Serum Lipid (cholesterol, HDL, LDL,triglycerides) levels after 4 weeks of drinking blueberry tea.	Fasting serum lipids (cholesterol, HDL, LDL,triglycerides) measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks
Improvement in fasting serum pro-inflammatory cytokine (IL-6, IL-1b, CRP, TNFa) levels after 4 weeks of drinking blueberry tea.	Fasting serum pro-inflammatory cytokines (IL-6, IL-1b, CRP, TNFa) assessed by ELISA will be measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks
Improvement in fasting serum albumin levels after 4 weeks of drinking blueberry tea..	Fasting serum albumin levels measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks
Fasting serum electrolytes (Na, K, Cl, HCO3).	Fasting serum electrolytes (Na, K, Cl, HCO3) measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks
Improvement in Resting Blood Pressure (central and brachial blood pressure) after 4 weeks of drinking blueberry tea.	Blood Pressure (central and brachial blood pressure) will be measured by Mobil-O-Graph and assessed on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks
Improvement in resting Augmentation Index after 4 weeks of drinking blueberry tea.	Augmentation index will be measured by Mobil-O-Graph and assessed on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks
Improvement in large artery stiffness after 4 weeks of drinking blueberry tea.	Large artery stiffness will be measured by Mobil-O-Graph and assessed on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).	4 weeks

Collaborators and Investigators

• Sponsor: Menzies Institute for Medical Research
• Investigators: Principal Investigator: Michelle A Keske, PhD, Menzies Institute for Medical Research

Publications and helpful links

General Publications

• DeFuria J, Bennett G, Strissel KJ, Perfield JW 2nd, Milbury PE, Greenberg AS, Obin MS. Dietary blueberry attenuates whole-body insulin resistance in high fat-fed mice by reducing adipocyte death and its inflammatory sequelae. J Nutr. 2009 Aug;139(8):1510-6. doi: 10.3945/jn.109.105155. Epub 2009 Jun 10.
• Martineau LC, Couture A, Spoor D, Benhaddou-Andaloussi A, Harris C, Meddah B, Leduc C, Burt A, Vuong T, Mai Le P, Prentki M, Bennett SA, Arnason JT, Haddad PS. Anti-diabetic properties of the Canadian lowbush blueberry Vaccinium angustifolium Ait. Phytomedicine. 2006 Nov;13(9-10):612-23. doi: 10.1016/j.phymed.2006.08.005. Epub 2006 Sep 18.
• Stull AJ, Cash KC, Johnson WD, Champagne CM, Cefalu WT. Bioactives in blueberries improve insulin sensitivity in obese, insulin-resistant men and women. J Nutr. 2010 Oct;140(10):1764-8. doi: 10.3945/jn.110.125336. Epub 2010 Aug 19.
• Couturier K, Batandier C, Awada M, Hininger-Favier I, Canini F, Anderson RA, Leverve X, Roussel AM. Cinnamon improves insulin sensitivity and alters the body composition in an animal model of the metabolic syndrome. Arch Biochem Biophys. 2010 Sep 1;501(1):158-61. doi: 10.1016/j.abb.2010.05.032. Epub 2010 May 31.
• Qin B, Nagasaki M, Ren M, Bajotto G, Oshida Y, Sato Y. Cinnamon extract prevents the insulin resistance induced by a high-fructose diet. Horm Metab Res. 2004 Feb;36(2):119-25. doi: 10.1055/s-2004-814223.

Study record dates

Study Major Dates

• Study Start: November 1, 2015
• Primary Completion (Anticipated): December 1, 2021
• Study Completion (Anticipated): December 1, 2021

Study Registration Dates

• First Submitted: December 3, 2015
• First Submitted That Met QC Criteria: December 10, 2015
• First Posted (Estimate): December 15, 2015

Study Record Updates

• Last Update Posted (Actual): April 6, 2021
• Last Update Submitted That Met QC Criteria: April 4, 2021
• Last Verified: April 1, 2021

More Information

Terms related to this study

• Keywords: type 2 diabetes; glucose tolerance; blueberry tea
• Additional Relevant MeSH Terms: Glucose Metabolism Disorders; Metabolic Diseases; Endocrine System Diseases; Diabetes Mellitus; Diabetes Mellitus, Type 2
• Other Study ID Numbers: H0014873

Plan for Individual participant data (IPD)

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