Effect of an Arabinogalactan Product
Condition: Postprandial Blood Glucose
Study type: Interventional

Summary: 
      Dietary fiber is an important nutrient that supports gastrointestinal function as well as
      blood glucose and cholesterol maintenance. The National Academy of Sciences Institute of
      Medicine (IOM) established an adequate intake for fiber as 14 g/kcal, or 38 g and 25 g for
      men and women, respectively. Currently, however, the majority of the U.S. population falls
      substantially below this level, with mean intakes of 18.9 g/day and 15.7 g/day in men and
      women age 20 and older, respectively. Fiber is a complex category that contains a number of
      different polysaccharides and oligosaccharides that are not digested in the upper
      gastrointestinal tract. In its final rule updating the Nutrition and Supplement Facts label
      regulations, which was published in May 2016, the U.S. FDA revised the definition of dietary
      fiber for food labeling and included two categories: (1) the intrinsic and intact
      non-digestible carbohydrate (NDC) and lignin, and (2) the isolated or synthesized NDC. In
      this re-definition, those NDCs that are isolated from plant and other food sources will now
      require clinical data indicating that the ingredient provides a physiological effect that is
      beneficial to human health.

      This study is designed to test the effect of an isolated NDC, arabinogalactan, on attenuation
      of blood glucose and/or insulin. Attenuation of blood glucose and/or insulin is one of the
      outcomes identified by the U.S. FDA as a physiological effect that is beneficial to human
      health, and as such, can be used to support that an isolated NDC is acting as a fiber (FDA
      2018). Arabinogalactans are hemicelluloses that are abundant in plants. Arabinogalactans are
      found in seeds, leaves, roots, and fruit of higher plants, such as cereals, beans, leeks,
      pear, corn, and wheat (Saeed 2011; Dion 2016). The arabinogalactan ingredient used in the
      study is isolated from larch (Larix laricina) using a patented water-based extraction
      process. Larch arabinogalactan has been designated as Generally Recognized as Safe (GRAS) by
      the U.S. FDA (2000) for multiple uses and has been used in numerous previous clinical studies
      in humans, with no significant safety issues observed at intakes of up to 30 g daily for up
      to 6 weeks. The present study was designed with the goal to assess the effect of acute
      consumption of arabinogalactan on blood glucose and insulin responses.
    

Detailed description: 
      The study is an acute, single-center, randomized, controlled, crossover trial with one
      screening visit (Visit 1; Day -7) and 3 test visits (Visits 2, 3, and 4; Days 0, 7, and 14).
      The three test visits are each separated by a 7-day washout period.

      At Visit 1 (Day -7), subjects will provide informed consent and a fasting capillary blood
      glucose will be assessed for eligibility purposes (fasting blood glucose must be ≥70 mg/dL
      and ≤125 mg/dL). At Visit 1, the following will also be conducted: medical history and prior
      and current medication/supplement use, inclusion and exclusion criteria, and vein access
      (using the Vein Access Scale; Appendix 2) will be assessed; and height, body weight, and
      vital signs will be measured; and BMI will be calculated. Fasting (12 ± 2 h) blood samples
      will be collected for chemistry and hematology, and female subjects <60 years old will
      undergo an in-clinic urine pregnancy test. Prior to release from the clinic, all subjects
      will be provided study instructions to follow before the next visit, which include:
      maintenance of adequate hydration and habitual diet/physical activity (throughout the study);
      fasting (12 ± 2 h, water only, prior to test visits); consumption of a diet that incorporates
      at least 150 g of total carbohydrate, refraining from vigorous physical activity (i.e.,
      sweat-inducing exercise), and alcohol consumption (24 h prior to test visits); and refraining
      from tobacco (1 h before and during test visits). Subjects will then be dispensed a 24-h Diet
      Record with instructions to record all food and beverage intake the day prior to the first
      test visit (Visit 2, Day 0) and released from the clinic.

      At Visit 2 (Day 0), subjects will arrive at the clinic fasted (12 ± 2 h, water only) to
      undergo clinic visit procedures (assessment for concomitant medication/supplement use, body
      weight, and vital signs). Eligible subjects will then be formally entered into the testing
      phase of the trial and assigned to a random test sequence. Adverse events (AE) will be
      assessed and subjects will be queried about compliance with study and test day instructions.
      Additionally, the 24-h Diet Record will be collected and reviewed. Subjects will undergo the
      glycemic/insulinemic response test with blood glucose concentrations obtained via capillary
      measurement and insulin concentrations assessed via venous measurement. An intravenous
      catheter will be inserted at least 10 min prior to the first blood sampling time. In order to
      maintain patency of the intravenous catheter, the catheter will be flushed with normal saline
      solution at least hourly. Blood samples will be drawn by venipuncture if the catheter fails.

      Baseline capillary and venous blood samples will be collected at t= -15 and -5 min prior to
      beginning the meal consumption. Subjects will be instructed to begin consumption of the
      breakfast meal at t = 0 min and required to consume the meal in its entirety within 10 min.
      Capillary and venous blood samples will then be obtained at t = 15, 30, 45, 60, 75, 90, and
      120 ± 5 min, where t=0 is the start of breakfast meal consumption. Additional venous blood
      samples will be collected as back-ups at all time points. Following the last blood draw, AEs
      will be assessed and subjects will begin their 7-day washout. Subjects will be dispensed a
      blank 24-h Diet Record with instructions to record intake the day prior to each test visit
      (i.e., Visits 3 and 4 (Days 7 and 14) and a copy of their first 24-h Diet Record with
      instructions to replicate their diet to the best of their abilities the day prior to each
      test visit (i.e., Visits 3 and 4 (Days 7 and 14). Subjects will also be reminded of the study
      instructions as per Visit 1, Day -7 (see above).

      At Visits 3 and 4 (Day 7 and 14), subjects will return to the clinic, crossover to the next
      study breakfast meal in their respective test sequence, and repeat the procedures from Visit
      2 (Day 0).
    

Intervention name(s): arabinogalactan
Intervention type(s): Other
Intervention description(s): Arabinogalactan will be mixed into sugar-free blackberry jam and consumed with the provided bread.
Other intervention name(s): control breakfast; bread plus jam
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: blood glucose; blood insulin; postprandial; fiber