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2006/12/15, 12:03 PM
I am no fan of GI/GL....it is so hit and miss, and unless you are diabetic, and even if you are, has little to no effect on your body composition. Recent evidence suggests so. It is difficult putting it mildly to figure what you are asking, another knock against the whole GI issue....
This is a paper written by Alan Aargon, pretty smart guy...
AFFECTING FACTORS
The interplay of many variables can either raise or lower GI, and are often difficult to control. Increased acidity, the presence of fiber, fat, and certain protein foods can lower glycemic response. Reduced particle size, greater ripeness, and heat in cooking can raise glycemic response.
GI do not necessarily help in predicting insulin response. Unfortunately for GI-conscious people, insulin is usually what they are trying to control. Despite having a very low GI of 15-36, milk and yogurt have a high insulin index equivalent to that of the high-GI white bread . Baked beans, another low-GI food, have a very high insulin index of 120. Cheese, beef, and fish have II's that are comparable to many carbohydrate foods.
Coingestion of fat with carbohydrate slows gastric emptying and thus the release of glucose into the blood, ultimately lowering GI. While this is usually true for GI, the degree of insulin response evoked by this combination is determined by the degree of the fat's saturation. For example, Collier & others observed that butter coingested with potato not only fails to lower postprandial insulinemia, it actually causes a synergistically heightened insulin response, even in healthy subjects .
Foods that should have a low GI due to their high fat content do not always have a low GI. Examples are fries, cookies, croissants, and doughnuts. Incidentally, these foods also have a high insulin index, presumably because their fat is mostly saturated. As of this writing, full-fat ice cream (low GI of appx 37) has not been tested for II, but it's safe to assume that it probably has disparate GI & II values.
Rasmussen & colleagues observed no increased insulin response with the addition of 40g or 80g olive oil, but saw a significant increase with 50g & 100g butter . Joannic's team observed a coingestion of carbohydrate with fats of increasing degree of unsaturation having a corresponding decrease in insulin response . A more recent study by Robertson & colleagues compared the effect of MUFA, PUFA, & SFA coingestion with carbohydrate and observed SFA's superior ability to raise postprandial insulin levels .
Coingestion of protein with carbohydrate is often recommended to lower GI. However, this doesn't necessarily lower insulin response. Carbs combined with protein in solution can pretty reliably raise insulin response synergistically. Gannon & Nutall's research on type-2 diabetics showed that coingested cottage cheese & glucose raised insulin levels beyond either food separately, indicating a synergistic effect . Van Loon & colleagues saw a similar phenomenon when comparing the insulin effect of various carb-protein/amino acid and carb-only solutions in normal subjects . Those containing free leucine, phenylalanine, & arginine, and the drinks with free leucine, phenylalanine, & wheat protein hydrolysate were followed by the largest insulin response (101% and 103% greater, respectively, than with the carb-only solution). These are only a few examples of many.
GI & OBESITY - SLIM CHANCE FOR CORRELATION
A systematic review of human intervention studies comparing the effects of high and low-GI foods or diets arrived at the following results :
---- In a total of 31 short-term studies, low-GI foods were associated with greater satiety or reduced hunger in 15 studies, whereas reduced satiety or no differences were seen in 16 other studies.
---- Low-GI foods reduced ad libitum food intake in 7 studies, but not in 8 other studies. In 20 longer-term studies (<6 months), weight loss on a low-GI diet was seen in 4 and on a high-GI diet in 2, with no difference recorded in 14 studies.
---- An exhaustive assessment of these human intervention trials found no significant difference in the average weight loss between low & high GI diets. in conclusion, the current body of research evidence does not indicate that low-GI foods are superior to high-GI foods in regard to treating obesity.
CONCLUSIONS (For Now)
GI is a useful tool that gives us clues to the behavior of certain foods, but that's exactly the main point of this article. Clues; mere hints are all we get from our current knowledge of GI. Successful application of GI is most consistent when we use higher GI sources to enhance the speed of postworkout glycogenesis, and that's about it. Carb foods are better judged on the basis of degree processing, refinement, or alteration/removal of micronutrition -- NOT on the basis of GI, or even GL. This is as good a time as any to crush the folly of what I call "food discrimination". A prime example of this is cutting out potatoes on the basis of GI. This happens all the time, & the dieter takes pride in thinking he/she is being prudent. Well, the critical thing to realize here is that all food species in nature have unique nutrient profiles. Therefore, unique nutritional benefit can be derived from each species. The natural matrix of plant &/or animal tissue cannot be duplicated in the lab, & hence there are many unidentified beneficial agents in, say, the humble potato. As a matter of trivia, it surpasses bananas in potassium & vitamin C concentration. Not to mention, it provides default hydration, and of course is a great whole-food source of starch. The list goes on & on.
Satiety, micronutrient density, insulin response, & surrounding factors altering glucose kinetics are all much like a roll of the dice in terms of bottom-line certainty & reliability of GI. Like all things in science - especially the deep bubbly cauldron that is applied nutritional science - it ain't all that simple. All avenues in this area are winding & complex.
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Maximus from Gladiator....Strength and Honor!
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