If you have diabetes, you probably know that the amount of carbohydrates you eat affects your blood glucose. But did you know that the type of carbohydrate is also important? This is because foods that contain the same amount of carbs can have different effects on your glucose. The glycemic index (GI) is a way of measuring the effects of a food on glucose levels. The GI looks at how high glucose levels rise and for how long after eating. Foods are ranked on a scale of 1-100. Foods that have a high GI (>70) are more quickly digested and absorbed and increase glucose more than foods with a lower GI (<55). The GI can be a helpful tool, but it’s important for people with diabetes to understand a little more about the GI.
- The GI is not a stand-alone diet. There are other important things to consider besides the GI of a food. Just because a food has a low GI doesn’t mean it’s a healthy nutrient-rich food choice. GI is only a measure of carb-containing foods. If a food doesn’t have carbs, it doesn’t have a GI. You still need a healthy meal plan that includes protein and fat to help manage diabetes. The GI of a food is affected by many factors including processing, cooking, origin of the food, variety of the food, and ripeness. This means that even the same foods could be different in their GI.
- The GI only measures the response of that food when eaten alone. The GI is tested only on single foods. When we eat, we usually eat more than one food at a time. In addition to eating carbs, we often eat protein and or fat. For example, if you ate plain bread your glucose after eating isn’t the same as if you ate bread with peanut butter.
- It’s not just the GI of the food, it’s the amount of the food you eat. If you eat more or less carbs, your glycemic response will change. The GI doesn’t take into account the portion of food usually consumed. So enter glycemic load (GL). The GL of a food is amount of carbohydrate multiplied by the GI divided by 100. Many fruits and vegetables that have a high GI actually have a low GL when considering usual portions.
- Studies have shown that a diet that includes more low vs. high GI and GL foods may help improve glycemic control. The American Diabetes Association does recommend eating lower GL foods. Studies show mixed results, but some studies show a reduction in A1C up to -0.5% by choosing lower GL carbs.
So what do you do now? If you are ready to make some changes to your diet, consider including more low GL foods. In general low GL foods include high-fiber fruits and vegetables, beans, lentils, whole grains, and milk. High GL choices are sweetened beverages, white rice, white bread, and other processed carbs. Remember that protein and healthy fats don’t contain carbs so they help to stabilize glucose. If you eat a food with a higher GI or GL pair with it some protein or healthy fats. Don’t think of this as another list of food rules for people with diabetes. The GI and GL are tools that can be used in combination with healthy meal planning for glycemic control. Enjoy what you eat and eat a variety of foods for a healthy diet.
by Christine McKinney, RD LDN CDE
