Why do some foods raise your blood sugar more than others? The glycemic index may help you unravel this mystery, while mindful eating provides you with the necessary perspective to use this information in a helpful rather than restrictive way.
What is the Glycemic Index?
As you probably know, focusing on the amount of carbohydrates in a meal is still the most powerful step toward understanding how foods affect your blood sugar levels (see Eat What You Love, Love What You Eat with Diabetes chapter 11, Clearing Carb Confusion). However, when you live with diabetes for a while, you quickly realize that not all carbohydrates affect your blood sugar the same way.
To understand what is happening to your blood sugar after you eat, it’s helpful to understand a concept called the Glycemic Index (or GI). The Glycemic Index is a ranking of carbohydrate-containing foods in terms of how much they raise your blood glucose. Individual foods are ranked from 0-100; glucose, the reference food, is 100. (Meats and fats are not included because they don’t contain carbohydrates.)
A food with a high glycemic index raises blood glucose higher than a food with a low glycemic index:
- 70 and up = High Glycemic Index (GI)
- 55-69 = Medium Glycemic Index (GI)
- 55 or lower = Low Glycemic Index (GI)
What affects a food’s glycemic index?
Unprocessed foods such as fresh produce and whole grains usually have a low to medium GI. Processed foods that have had their fiber removed or sugar added will typically have a higher GI. For example, in this list of the GI of 100 common foods, 100% whole grain bread has a GI of 51 whereas white bread has a GI of 75.
The glycemic index can provide you with information about the effect of one food relative to another, but there are a number of limitations to the GI. For one, not all foods are labeled or indexed. Further, the glycemic index is based on 100 grams of a particular food – which doesn’t reflect the serving size actually eaten. Another important limitation is that the GI index refers to a single item but the other foods you eat in a snack or a meal will affect the glycemic index. To complicate things further, the more ripe a fruit or vegetable is, the higher its GI is likely to be. GI is also affected by the cooking method and the cooking time.
What is glycemic load?
The glycemic load (or GL) gives a more accurate picture of a food’s impact on blood sugar. The glycemic load is calculated by multiplying the grams of a carbohydrate in a serving by the glycemic index, then dividing by 100.
- 20 or higher = High Glycemic Load (GL)
- 11-19 = Medium Glycemic Load (GL)
- 10 or lower = Low Glycemic Load (GL)
For example, using this list of the GI and GL of 100 common foods, watermelon has a glycemic index of 74 which would be considered high. However, since a serving of watermelon is relatively low in carbohydrate, its glycemic load is only 4 which is considered low!
How do you use the Glycemic Index with Mindful Eating?
While all this arithmetic is wonderfully interesting for scientist and nutrition professionals, it can really drain the enjoyment from a meal by making eating into a math test. Mindful eating provides the perspective needed to make this kind of nutrition information helpful but not restrictive, punitive, or distracting.
Here are just a few examples of how you can apply the Mindful Eating Cycle concepts and techniques that we described in Eat What You Love, Love What You Eat with Diabetes to use the glycemic index to help you manage your diabetes.
- When Do I Eat? As you remember from chapter 5, When do I Want to Eat?, hunger is caused by a falling blood sugar level. If you have developed a habit of choosing “quick” energy foods, you may experience a rapid rise and then fall of your blood sugar, creating a vicious cycle of hunger. Your awareness of this cycle might lead you to experiment with lower GI or GL foods and foods that lead to more lasting satiety such as protein.
- What Do I Eat? We strongly believe in an “all-foods-fit” approach to nutrition! In the Eat What You Love, Love What You Eat Diabetes Plate, the upper right hand corner indicates foods that contain carbohydrates including grains, starchy vegetables, fruit, fruit juice, milk, yogurt, sweets, and desserts (see chapter 7 for a complete explanation). While the total amount of carbohydrate you eat at a snack or meal is the most important (and relatively simplest) information for helping you decide what to eat, the GI and GL can help you experiment with different types of carbohydrates to measure their effect on your blood sugar. For example, if you are really in the mood for dessert, you might balance it with carbohydrate-containing foods with a lower GI.
- How Do I Eat? Eating with the intention of satisfying hunger, enjoying your food, and/or managing your diabetes will help you decide what is most important for you to pay attention to at any particular meal.
- How Much Do I Eat? Again, the GI of a food is based on a reference amount of that food, not on how much you eat of that food. Paying attention to satiety and testing your blood sugar two hours after the first bite of a meal will help you learn more about how your body processed that food.
In short, while glycemic index and glycemic load provide potentially useful information, the priority is making decisions based on what works for you.