Effect of 6-week Strawberry Supplementation on Insulin Action (STR2)
Condition: Insulin Resistance; Nutritional Disease; Metabolic Disease
MeSH terms: Insulin Resistance; Metabolic Diseases; Nutrition Disorders
Study type: Interventional

Summary: 
      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.
    

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.
    

Intervention name(s): Strawberry; Placebo1; Placebo2
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): 20g twice per day (BID) in beverage; Placebo Beverage 1 without fiber; Placebo Beverage 2 with Fiber
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: Insulin Resistant; Dietary Supplements; Nutrition; Antioxidant; Inflammation