Q:  My doctor told me to avoid foods with a high glycemic index to help my issues with metabolic syndrome.  What is the glycemic index?

A:  The havoc that rapidly rising blood sugar levels can have on both our health and weight is well-documented. Researchers have long known the importance of controlling blood sugar levels in those with diabetes, but it turns out that blood sugar levels are critically important for everyone including those with metabolic syndrome. Rapid blood sugar spikes lead to increased insulin levels, inflammation in the body, and decreased energy levels when the blood sugar levels later begin to dip. Further, these problems can in turn lead to more problems, such as chronic disease (i.e. metabolic syndrome) and weight gain.

Since controlling blood sugar levels is so vital for all people, the question then becomes what is the optimal way to maintain healthy, stable blood sugar levels. Two ways of looking at the effects certain foods have on our insulin spikes and thus overall health is to look at glycemic index and glycemic load.

Glycemic Index (GI). The Glycemic Index is a measure of how quickly blood sugar levels rise after eating any particular food in comparison to how quickly blood sugar levels rise after eating pure sugar (glucose). The GI of pure sugar is 100. Foods with a GI score of less than 55 are considered to be low GI foods, foods with a GI of 56-69 are medium GI foods, and foods with a GI of 70 or higher are considered to be high GI foods. Selecting low GI foods like whole grains is encouraged and avoiding high GI foods like white bread is discouraged. Other than the GI number of a food, no emphasis is made on the quality of foods consumed or on any other aspects of what the food may do to our bodies.

Glycemic Load (GL). The Glycemic Load formula picks up where the Glycemic Index leaves off. The GL takes into account not only how quickly a food causes blood sugar levels to rise, but also takes into account portion size and carbohydrate density. The GL takes how many carbohydrates a food item has, multiples that by its GI value and then divides that total by 100. A food with a GL of 20 or above is high; 11 to 19 is moderate; 10 or below is low. Using these guidelines people can make more informed decisions about the impact consuming a food will have on them, but again the impact on blood sugar is the only selection criteria as to whether or not a food is beneficial to eat.         

Some examples of the GI and GL of various foods are listed below:

Food Serving Size Glycemic Index Glycemic Load
White Wheat Flour Bread 30 grams 71 10
Apple Juice 250 mL 44 30
White Rice 150 grams 89 43
Ice Cream 50 grams 57 6
Banana 120 grams 62 16
Watermelon 120 grams 72` 4
Black Beans 150 grams 30 7


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