Clyde, A key point which I think might be glossed over in your guide (Endurance Nutrition Book) is the rate of digestion (I suppose this is glycemic index?). If I eat a piece of fruit with X grams of carbs vs malto with X grams of carbs isn't the onset and peak of blood sugar quite different? Does the liver have to process fructose into glucose before insulin response? What if I don't chew it much, or chew it a lot? I though it would be interesting to take blood sugar readings after eating 5, 10, 20, 40 cherries (or something), to see what actually happens in a real body, as opposed to assumed response. Lloyd
ANSWER: Yes to all points. Only glucose generates a rapid insulin response (the pancreas releases insulin primarily in reponse to glucose, amino acids and potassium) because other sugars have to be converted into glucose by the liver first. Fruit sugar is sucrose, which is half glucose and half fructose. If you don't chew your food much it takes longer for the stomach to break the larger pieces of food down to sub-millimeter size and therefor it takes longer before the stomach empties the food into the small intestine, which reduces the rate at which the calories are digested and enter the bloodstream. A very interesting application of this idea is in finely versus coarsely ground whole grains. Studies show that digestion and the rise in blood sugar are faster when consuming whole grains that are finely ground (such as many whole grain breads on the market that feel as soft as white bread) as opposed to coursely (stone ground) breads, which often also contain chunks of seeds and nuts making them even coarser than the stone ground grains would by themselves. In other words, even if the sugar type is identical (in this case glucose from whole grains) and the total amount of fiber is identical (whether you finely or coarsely grind grains into flous does not change the amount of fiber, since cellulose fiber is a molecule and molecules are not chemically broken down by macroscopic processes), even how finely the food is ground down before the product is made contributes to digestion rate and therefore its effectiveness for muscle fueling. Slower digestion is better. but before and during intensive training high fiber foods that are coarsely ground are much more likely to cause stomach upset, so those are times when you would want to switch the coarsely ground foods or even any foods containing fiber with maltodextrin or other refined (low- or no-fiber) sugars. To compensate for the crazy-fast digestion of such carbohydrates you consume them piecemeal over time as you consume fluids. Pacing your intake of them compensates for the fact that once they enter the stomach they are almost immediately emptied into the intestine and then into the bloodstream. In terms of regular food, digestion rate decays exponentially after it peaks soon after eating. The more food in the stomach and intestine, the faster digestion occurs in an absolute sense (more food equals more digestion) but not in a relative sense (very large amounts of food equals more digestion but transport into the bloodstream can become saturated so that some of the food can't be absorbed and has to wait). So as you eat more cherries (in your proposed experiment) your absorption rate into your bloodstream would increase but eventually plateau as you eat more and more and more. There is an upper limit to the rate. But that would be a lot of cherries.
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