What is the Glycemic Index?

Some of you may have heard the term “glycemic index” thrown around in the diabetes community and you have no clue what that means. That’s perfectly fine, here’s an entrance in to the topic of the glycemic index.

The glycemic index (GI) is a system that ranks foods on a scale from 0 to 100 based on their effect on blood sugar levels. The higher the number, the faster the food effects your blood sugar level. However, there is another term that goes hand in hand with glycemic index and that’s glycemic load (GL). The glycemic load is how much of that certain food will negatively or positively affect your blood sugar levels.

For example, watermelon is an 80 on the GI, but there is relatively low amounts of digestible carbohydrates in a typical serving of watermelon, usually 3/4 cup. The GL value of watermelon is then 5, meaning it’s high in sugar but if you control the portion size, it won’t affect your blood sugar too much. You’d have to eat a whole watermelon by yourself for you to experience a negative effect on your blood sugar levels.

The GI helps to categorize foods as either slower-acting good carbs or fast-acting bad carbs. This reflects on how fast your body converts carbs into glucose. The smaller the value, the less of an impact the food will have on your blood sugar levels.

Glycemic IndexGlycemic Load
55 or lower = Low/Good1-10 = Low
56-69 = Medium11-19 = Medium
70+ = High/Bad20+ = High

Food package labels might have the glycemic index for reference. If the labels don’t have anything, you can find a list of common foods online.

If you don’t find the food you’re looking for on the list the general rule of thumb is if the food is closer to its natural form it will have a lower value compared to a refined or processed food which would have a higher value.

There are other factors that can affect a foods GI value such as how it’s prepared, if the fruit is ripe, or what kinds of other foods you eat with it.

For example, carrots are fairly low in value. It’s best eaten steamed or raw. If you boil them, they lose some nutritional value and can break down in to glucose easier when digested than when raw making their GI value go up. If you eat raw carrots with ranch dressing, that increases the GI value. If you eat a whole bad of baby carrots, you can bet that’ll have an affect on your blood sugar.

Other factors that can affect GI is yourself personally. Your age, metabolism, and activity level all affect how your body reacts to carbs. So when looking at the Glycemic Index of a food, don’t take the number at face value just note that if it’s in the low category, then it’s good. If not, then be careful how much you eat.

Portion sizes really matter when it comes to Glycemic Index. Just because something is healthy, doesn’t mean you should eat a ton of it.

To recap, glycemic index and glycemic load should be taken with a grain of salt but do let it guide you to make the right dietary decisions in your life. Be aware of how the carbs in the food can affect your blood sugar level and don’t eat too much. Too much of a good thing can be a bad thing.


Mayo Clinic

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