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Effect of 6-week Strawberry Supplementation on Insulin Action (STR2)

This study is ongoing, but not recruiting participants.
California Strawberry Commission
Information provided by (Responsible Party):
Institute for Food Safety and Health, United States Identifier:
First received: October 19, 2011
Last updated: February 6, 2017
Last verified: February 2017
The primary study objective is to investigate the potential chronic beneficial effect of polyphenolics derived from strawberry on impaired insulin signaling in insulin resistant individuals through their ability to modulate oxidative- and inflammatory-markers that lead to devastating disease, including, but not limited to, diabetes and cardiovascular disease.

Condition Intervention
Insulin Resistance
Nutritional Disease
Metabolic Disease
Dietary Supplement: Strawberry
Dietary Supplement: Placebo1
Dietary Supplement: Placebo2

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Participant
Primary Purpose: Treatment
Official Title: Effect of 6 Weeks Strawberry Supplementation on Insulin Action and Associated Risk Factors in Insulin Resistant (IR) Subjects (STR2)

Resource links provided by NLM:

Further study details as provided by Institute for Food Safety and Health, United States:

Primary Outcome Measures:
  • The chronic beneficial effect of polyphenolics from strawberry on impaired insulin signaling in insulin-resistant men and women [ Time Frame: 10 weeks ]
    Subjects will be randomized to receive either one of beverages, Pbo1, Pbo2 or Str Beverage and consume randomly assigned beverage twice per day with their breakfast and dinner meals for 6 weeks. On visits at Wk0, Wk6, and Wk10, blood will be collected at 0h, and 1h, 2h, 3h and 4h time points following the 75 g glucose load (oral glucose tolerance test) and Flow Mediated Dilation (FMD) procedure will be performed as well.

Secondary Outcome Measures:
  • The chronic beneficial effect of polyphenolics from strawberry on oxidative- and inflammatory-markers in insulin-resistant men and women [ Time Frame: 10 Weeks ]
    Samples of venous blood will be collected for measurement of oxidative and inflammatory markers (hs-CRP levels, LDL oxidation, Interleukin (IL)-6 and other inflammatory molecules, Total antioxidant levels of the blood)

Enrollment: 45
Study Start Date: October 2011
Estimated Study Completion Date: December 2018
Estimated Primary Completion Date: December 2018 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Placebo Comparator: Placebo1
Placebo Beverage 1 without fiber
Dietary Supplement: Placebo1
Placebo Beverage 1 without fiber
Active Comparator: Strawberry
Strawberry Beverage 20g/BID
Dietary Supplement: Strawberry
20g twice per day (BID) in beverage
Placebo Comparator: Placebo2
Placebo Beverage 2 with Fiber
Dietary Supplement: Placebo2
Placebo Beverage 2 with Fiber

Detailed Description:

This study is a single-center, randomized and single blinded, placebo-controlled, 6-week, parallel design study with follow-up to evaluate strawberry-associated chronic improvements in insulin action resulting in reduced whole body insulin resistance and improved glucose tolerance. This study will take approximately 11~12 weeks.

Subjects will follow an extremely limited polyphenolic diet throughout the duration of their participation in the study.

The limited diet will begin 7 days before the first study visit and end before the last study visit. Following the polyphenol-free 7-day run in period, at Week 0, subjects will be scheduled to return to the Center for sequence randomization, an Oral Glucose Tolerance Test (OGTT) as well as a Flow Mediated Dilation (FMD) procedure to measure endothelial function. Subjects will incorporate either one of tow Placebo Beverages (PBO1, n=15; PBO2, n=15) or Strawberry Beverage (STR, n=15, an optimal strawberry test dose of 40 g/d) into their diet daily for a period of 6 weeks. Subjects will consume randomly assigned beverage twice per day with their breakfast and dinner meals.

All subjects will be asked to come to the Center once a week where they will receive a week's supply of beverages. Additionally, fasting clinical and laboratory variables, anthropometrics, and vital sign measurements will be assessed at each bi-weekly visit at Week 3 and Week 5.

Participants will undergo the same procedures at the end of Week 6: fasting blood sample collection for analysis of insulin, glucose, oxidative and inflammatory markers, an OGTT to assess glucose handling, as well as a FMD procedure to assess endothelial function in response to 6 weeks of either the Placebo or Strawberry treatment.

Subjects will be required to visit the Center 4 weeks after the end of their intervention period (Week 10), at which time they will undergo their last anthropometrics and vital sign measurements, a 4 hour OGTT, and the FMD procedure.


Ages Eligible for Study:   18 Years to 65 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Must meet ONE or MORE of the criteria (1)-(5) associated with insulin resistance along with all other criteria listed (6)-(9):

    1. Blood glucose concentration between140-199 mg/dL at 2hr from OGTT.
    2. Elevated fasting glucose (110 mg/dL≤ Fasting blood glucose <126 mg/dL)
    3. Elevated fasting insulin (>75th percentile cutoff of 13.13 μU/mL)
    4. Insulin resistance defined by the homeostasis model assessment method of insulin resistance (HOMA-IR) (glucose [in millimoles per liter] × insulin [in microunits per milliliter]/22.5) values of at least 2.5.
    5. Waist circumference ≥ 110 cm because many epidemiology studies have been shown that waist circumferences may be related to insulin resistance.
    6. Nonsmokers
    7. Not taking any medications that would interfere with outcomes of the study, i.e. lipid lowering medications, anti-inflammatory drugs, or dietary supplements
    8. 18 years of age and older
    9. No clinical evidence of cardiovascular, metabolic, respiratory, renal, gastrointestinal or hepatic disease

Exclusion Criteria:

  • Pregnant and/or lactating.

    • Allergy or intolerance to strawberries and dairy products.
    • Current regular consumption of strawberries is > 2 servings per day.
    • Fasting blood glucose ≥ 126 mg/dL. Subjects identified with elevated fasting blood glucose levels will be advised to contact their primary care physician for appropriate follow-up care.
    • Taking over the counter antioxidant supplements or other supplements that may interfere with the study procedures or endpoints.
    • Subjects with unusual dietary habits (e.g. pica).
    • Actively losing weight or trying to lose weight (unstable body weight fluctuations of > 5 kg in a 60 day period).
    • Excessive exercisers or trained athletes.
    • Subjects with documented atherosclerotic disease, inflammatory disease, diabetes mellitus, or other systemic diseases.
    • Addicted to drugs and/or alcohol.
    • Medically documented psychiatric or neurological disturbances.
    • Smoker (past smoker may be allowed if cessation is > 2 years).
  Contacts and Locations
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Please refer to this study by its identifier: NCT01457612

United States, Illinois
Clinical Nutrition Research Center
Chicago, Illinois, United States, 60616
Sponsors and Collaborators
Institute for Food Safety and Health, United States
California Strawberry Commission
Principal Investigator: Indika Edirisinghe, Ph.D Institute for Food Safety and Health
Principal Investigator: Britt Burton-Freeman, Ph.D Institute for Food Safety and Health
  More Information

Responsible Party: Institute for Food Safety and Health, United States Identifier: NCT01457612     History of Changes
Other Study ID Numbers: STR2 2011-076
Study First Received: October 19, 2011
Last Updated: February 6, 2017

Keywords provided by Institute for Food Safety and Health, United States:
Insulin Resistant
Dietary Supplements

Additional relevant MeSH terms:
Insulin Resistance
Metabolic Diseases
Nutrition Disorders
Glucose Metabolism Disorders
Insulin, Globin Zinc
Hypoglycemic Agents
Physiological Effects of Drugs processed this record on May 22, 2017