by Glen Herbert
The glycemic index is a very complicated thing, actually, and you can spend a lot of time with the minutia. But there is a short form, one which describes in a useful way the very basics of the concepts that arise from an understanding of what the glycemic index is. And, this is what it is: It is a metric used to describe a food’s effect on a person’s blood glucose, or blood sugar. As a measure, it is objective. As an index, the result are numbers, each food rated in a way that can make it comparable, on this one point, with all others. Most foods have a GI between 50 and 100. The index is useful for understanding how your body breaks down carbohydrates, though it’s application can be complicated because there are lots of things that affect GI, such as ripeness, how a food has been cooked, the longer it has been cooked, how fresh it is vs. how long it has been stored.
But, again, the numbers and the minutia are really not as important as the concept: foods with a high glycemic index release glucose more quickly, which results in a spike in blood sugar. The bigger the spike, the bigger the rush of energy we will feel, and indeed the more energy we will have at our disposal. Athletes use the index as a means of ensuring that they have a great burst in energy at that moment that they need it in competition, such as distance runners binging on pasta the night before race.
But, what goes up must come down, and the drop in energy is in kind with the spike: If it was quick and high, then the drop in blood sugar that follows will be quick and low. It will act as a signal to your body that you need more fuel—food with a high GI—in order to counterbalance the drop in blood sugar, and you’ll feel hungry.
Big spikes, followed by big drops, is one of the reasons that we overeat.
Big spikes, followed by big drops, is one of the reasons that we overeat. Refined carbohydrates—white bread, pasta, breakfast cereal, refined sugar, and so on—have a high GI, which means they give us a fast, bit spike in energy. Then we have the corollary jones and head for the kitchen for the next dose of refined carbohydrate … and on and on, up and down with high highs and low lows. You overeat, you make poor choices, and pretty soon you need to buy bigger yoga pants.
For those of us who aren’t extreme athletes, a better idea is to shift our diets, generally, to foods with a lower GI, evening out the highs and lows. That way we won’t have those hunger spikes and will feel satisfied longer. The mechanism is (in a very small nutshell, but this will do for the time being) insulin. Insulin transports sugar (glucose) from the blood stream into the cells of the body, including, of course, muscle cells. In increases protein synthesis, i.e., building muscle. It also transports amino acids into muscle cells and reduce protein breakdown, i.e., keeping the muscle cells that we already have. Foods with a high GI spike insulin, and spike all the things that insulin does. But, if we aren’t using that energy, insulin then is part of the mechanism that converts it into stored energy for later: fat on the body.
The concept behind the GI is the basis for some of the fad diets that are circulating, such as low carb or wheat belly diets. Those diets appeal to people because they are binary—they suggest that only one operator, such as wheat, is the source of all our ills. Because they are based in a clumsy stab at evening out the glycemic index, they will have some affect, at least initially. People who cut their carbs drastically will feel less hungry and think, “hmm, this wheat belly thing really works.”
However, nutrition is more complicated than that. Carbs aren’t bad, but we can make better carb choices generally—some carbs are significantly better than others, and we need to get a handle on their representation in our diet. In North America, it’s hard to find a meal that isn’t loaded in fast carbs, and so we’re binging on them every meal of the day. It’s not always intuitive: Parsnip has a high GI, while beans have a low GI. Sweet fruits like peach and strawberries have a medium GI, while potato has a high GI. You need to know some of this, and to use that knowledge in order to make the right decisions, but even more important is getting a handle on the really fast carbs. They aren’t poison, but we generally eat a diet that is shifted significantly to the carb end of the food spectrum.
Broccoli, Cauliflower, Romaine lettuce, Cucumber, Mushrooms, Asparagus, Green beans, Zucchini; small seeds (sunflower, flax, pumpkin, poppy, sesame); most whole intact grains (durum/spelt/kamut wheat, millet, oat, rye, rice, barley); most vegetables, most sweet fruits (peaches, strawberries, mangos); tagatose; fructose
Oats , Sweet potato, Brown rice, Navy beans, not intact whole wheat or enriched wheat, pita bread, basmati rice, unpeeled boiled potato, grape juice, raisins, prunes, pumpernickel bread, cranberry juice, regular ice cream, sucrose, banana
Apple, Pear, Banana, Plum , Peach, Nectarine, Strawberries, Blue berries, Raspberries, Honey, Maple Syrup white bread (only wheat endosperm), most white rice (only rice endosperm), corn flakes, extruded breakfast cereals, glucose, maltose, maltodextrins, potato, pretzels, parsnip, bagels