The Glycemic Index – why you should take it with a grain of salt

In recent years, the glycemic index has received a lot of attention from various media and health agencies, with many proclaiming it as the be-all-end-all measurement in nutrition.  What exactly is it?  The glycemic index (G.I., for short) is a scale that gives a measure of how rapidly blood sugar levels are raised after ingesting a given type of food.  This scale estimates how much each gram of available carbohydrate (which is the number of carbohydrates minus the carbohydrates that come from fiber) in a particular food elevates an individual’s blood glucose levels upon consuming the food, relative to if the individual had consumed pure glucose.  Because glucose is used as the metric for comparison, it is given a value of 100 on the glycemic index.  Despite being touted by lots of people as an important measurement, the G.I. has a number of flaws, and the G.I. values of foods should be scrutinized and taken with a grain of salt.

The main problem with the G.I. occurs with the methods of figuring out the values for certain foods.  All G.I. studies are conducted on individuals who have fasted overnight, with these individuals consuming the foods in question in an isolated manner.  While this may give an accurate measurement of how strongly a particular food could raise an individual’s blood sugar, it simply isn’t practical.  For one, most individuals eat foods in a non-fasted state, with the substrate of their previous meals undergoing digestion as the most recent meal is being eaten.  Additionally, even when individuals do consume foods in a fasted manner (such as at breakfast), they are probably consuming a variety of foods that collectively make up their breakfast.  When this happens, the G.I. value of the food in question becomes irrelevant because the true G.I. value of the meal becomes a combination of all of the foods being ingested.  Coingesting protein and fat with carbohydrates can greatly slow the gastric emptying of the food, which also ends up slowing down the release of glucose into the bloodstream.

One additional problem that the G.I. creates is that it causes many people to view certain foods as “taboo” items, with these individuals fearing that consumption of these foods will be the bane of their existence, giving them a destiny of developing diabetes.  The fact is that each food species on earth has a unique nutritional profile, providing a unique nutritional benefit to those who choose to eat it.  What’s more, there remains a great deal to be studied regarding the compositions of various food species, so it’s safe to assume that there are numerous unidentified benefits to consuming certain foods that we haven’t even discovered yet!  Don’t let the G.I. fool you – a well-rounded diet containing foods from all food groups with lots of diversity is easily the best type of diet that you can have.  Also, if there are high G.I. foods that you like, don’t worry too much about consuming them – just make sure that you have them as part of a well-balanced meal with protein and fat included and also consume the food in question in moderation.

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