The glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels.
The GI has been promoted as a method to construct a healthy diet, and has been touted to diabetics as a way to control their blood glucose levels. The definite implication is that low GI equals healthy.
The only problem is that the concept is a grotesque oversimplification that has no applicability to the real world. My latest HND article discusses the GI and its limitations.
To calculate the GI, testing of an individual food item is performed on ten healthy subjects, who consume a measured amount of the food. Their blood glucose levels are monitored at frequent intervals over a two hour period. The data is then averaged and the GI for this food is established. However, GI data for a particular food can vary widely from lab to lab.
Those familiar with blood glucose levels will tell you that they can be affected by a host of things, including stress, and any inflammatory processes going on in the body. It is remarkable that even the most basic physiological controls are not done on the subjects, to eliminate confounding factors. Besides, foods, being biologic, are not identical from sample to sample.
The random errors alone could be substantial, and let's not even bother with the systematic errors inherent in the blood glucose measurement itself.
Moreover, even if consistent data on the pure food could be obtained, there are few real life instances whereby a single food item is actually consumed. White bread could have a particular GI, which would be drastically lowered if butter were applied. Depending on the vinegar content and amount of time it has been refrigerated, the GI for potato salad can be affected—and not by a small amount, either.
Finally, low GI does not equate with healthy. There are many decidedly unhealthy foods with a low GI.
It is appalling that so-called scientists are promoting this nonsense. It is long past time that someone exposed the GI for what it is: Just one more diet scam. Read the complete article.