Is the glycemic index the new key to healthy eating?
This is the main problem with the Glycemic Index. There’s no standard way of calculating it. If I give you a food item, you can use science to tell me the number of calories, the amount of protein, carbohydrates, fat, nutrients, etc. Any decent lab could do this and come up with the same numbers.
The Glycemic Index depends upon the digestive systems of the volunteers (normally college kids), the way the food is prepared, and how it is consumed. Two labs can do the glycemic index of the same product and come up with wildly different numbers. Even worse, it’s really expensive to do. Most of the Glycemic Index calculations are the results of a single lab with maybe no more than a 1/2 dozen or so volunteers.
Another issue is the sheer amount of food stuff that may have to be consumed. The Glycemic index depends upon someone digesting a fixed amount of carbohydrates and seeing how it affects the blood glucose of the volunteer after certain periods of time. The volunteer is given say 50 grams of pure glucose, then tested an hour, two hours, and three hours after finishing the glucose. Then, the volunteer is given 50 grams of carbohydrates in the form of the food being tested, and again the blood glucose is tested again at the same periods of time. The Glycemic Index is the ratio of that food compared to the glucose based upon 100.
For example, to get 50 grams of carbohydrates in carrots, you have to eat about 4 1/2 cups of carrots.
The Glycemic Load was developed because the Glycemic Index seemed to create discrepancies. Carrots are a good thing to eat and don’t affect blood glucose, but they have a high GI. So, the Glycemic Load takes the Glycemic index and divides it by the number of carbohydrates found in the typical serving size (one ounce? Four ounces?). Anyway, this saves carrots by giving them a low, low, Glycemic Load.
Of course, there’s a possibility that carrots’ Glycemic Index was miscalculated to begin with. Later tests on carrots have changed the Glycemic Index from 71 (fairly high) to 47. (low).
The Glycemic Index is an interesting concept, but due to variations in measurements, just cannot be scientifically validated.