Postprandial Glycemic Response to Polyphenol-fortified Snack Bars
Condition: Blood Sugar Response
Study type: Interventional

Summary: 
      Consuming plant chemicals (e.g., polyphenols) may have beneficial effects on human health
      that, if confirmed, may warrant inclusion in combat rations. Ration developers would like to
      determine whether the fortification of a high sugar food item with a polyphenol-rich
      freeze-dried fruit and/or a fruit extract improves blood sugar response and promotes other
      positive physiological changes (e.g., satiety) in a dose-response manner. This study will
      test four different types of snack bar with various polyphenol doses, and compare blood
      response to a snack bar without polyphenols.
    

Detailed description: 
      High glycemic index (GI) foods generally contain simple sugars and/or highly processed and
      refined carbohydrates (e.g., instant oatmeal and white bread). These foods are rapidly
      digested, which raises blood glucose and insulin to higher concentrations and more rapidly
      compared to low GI food items. In some situations, it is advantageous to consume high
      glycemic response food items to promote recovery from intense exercise/work. However, there
      is some suggestion that low/moderate-GI foods may better maintain glucose levels and enhance
      performance if consumed before and during prolonged exercise. Further, impaired blood glucose
      regulation (e.g., that can occur with chronic intake of high GI foods) may stimulate the
      development of oxidative stress, inflammation, dyslipidemia, insulin resistance, and
      diabetes; and, it is associated with changes in body weight due to stimulating hunger and
      excessive food intake. These negative consequences are concerning, given the prevalence of
      overweight/obesity and comorbidities (including metabolic syndrome) within the Department of
      Defense (DoD). Polyphenols are a heterogeneous group of phytochemicals that are found in
      plant-based foods; and they have antioxidant and anti-inflammatory properties that may
      ultimately help protect against chronic diseases, such as cancer and cardiometabolic disease.
      Berry polyphenols are predominantly comprised of proanthocyanidins and/or ellagitannins
      (collectively referred to as "tannins"); and, berries have been shown to promote glycemic
      control when consumed with a high-carbohydrate containing food item. These beneficial health
      effects may warrant polyphenol fortification of combat rations and Garrison food items. For
      example, Natick Soldier Research, Development and Engineering Center's (NSRDEC) Combat
      Feeding Directorate demonstrated that tannins extracted from berries effectively inhibits the
      activity of enzymes that metabolize starch in vitro, an underlying mechanism for slowing
      starch digestion in vivo. However, whether consumption of a high GI food item containing
      polyphenol-rich freeze-dried fruit and/or fruit extracts improves glucose control, reduces
      oxidative stress, and promotes satiety in human volunteers is unknown. In this randomized,
      cross-over, placebo-controlled, dose-response trial, at least 20 civilian and/or military
      personnel will be asked to consume one of five food items during separate trials: 1) a high
      glycemic snack bar (control) without any fruit ingredients; 2) a high glycemic snack bar with
      cranberry extract (0.5% total weight); 3) a high glycemic snack bar with cranberry extract
      (1% total weight); 4) a high glycemic bar with freeze-dried black raspberries (10% total
      weight); and, 5) a high glycemic snack bar with freeze-dried black raspberries (20% total
      weight). Serial blood sampling to measure acute changes in circulating glucose, insulin,
      gastrointestinal hormones and biomarkers of oxidative stress and satiety will occur at
      baseline and for three hours after consumption of each food. Appetite will also be assessed
      at an ad libitum meal after the three hour period. The only known risks, which this study
      presents to participants, are those associated with venous catheter placement. The fruit
      concentrates for the present study are either commercially available (black raspberry
      powders) or used as an ingredient to boost the phenolic content of commercial items
      (cranberry extract). The results will help determine whether fortifying high glycemic food
      items with polyphenols may benefit the Warfighter in the ration- or Garrison-feeding
      environment.
    

Intervention name(s): Fruit extracts high in polyphenols; placebo
Intervention type(s): Other; Other
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: high glycemic index, polyphenols, blood glucose, satiety