Episode 8 – starch digestibility and limitations of the glycemic response

In episode 8 of the Break Nutrition show we discuss 2 papers which explore the glycemic, insulin and incretin responses and how the digestibility of starch as well as the apportioning of endogenous vs exogenous glucose comes into play.

The paper from 2012 is “Slowly and rapidly digestible starchy foods can elicit a similar glycemic response because of differential tissue glucose uptake in healthy men” http://www.ncbi.nlm.nih.gov/pubmed/22990033.

The paper from 2015 is “Plasma glucose kinetics and response of insulin and GIP following a cereal breakfast in female subjects: effect of starch digestibility” http://www.ncbi.nlm.nih.gov/pubmed/25852025.

  • 2 foods with identical glycemic responses can stimulate GIP and insulin to significantly different degrees
  • 2 foods with identical glycemic responses can derive different proportions of glucose from endogenous production vs exogenous absorption
  • The apportioning of endogenous vs exogenous glucose depends in large part on the rate of starch digestion and rate at which glucose is cleared (the latter is significantly dependent on tissue glucose uptake)
  • measuring blood glucose (your glycemic response) after consuming a food or meal is marginally useful and has significant limitations:
  • if your blood glucose is excessively high and/or unstable, this confirms your inability to handle the food appropriately
  • if your blood glucose remains relatively low and stable, this does not confirm your ability to handle the food appropriately because the physiological ‘cost’ in terms of insulin, GIP and other responses are not factored in
  • Fiber, again, does not seem to be a considerable factor affecting these metabolic responses
  • The speed at which starch is digested is largely dependent on the degree and type of processing incurred by the macromolecular starch network

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