Dear Dietitian: Glycemin Index


Dear Dietitian,

I have had diabetes for fifteen years and have kept it under control. But recently, my blood sugars have been higher, around 200 during the day. My daughter thinks I should try the glycemic index diet. What do you think?


Dear Terry,

The glycemic index diet was introduced by Jenkins et al. in the early 1980s as a ranking system for carbohydrates based on their immediate impact on blood glucose levels (1). It was developed as a meal-planning guide for people with diabetes, with emphasis on low glycemic index foods. The premise is to choose low GI foods to help control blood sugar levels and avoid spikes. The GI concept has since expanded to include weight loss and disease prevention, although its benefits in these areas have not been backed by science.

The GI system ranks foods from 0 to 100; the smaller the number, the less impact it has on your blood sugar. Glucose is given the value of 100; all other foods are ranked comparatively to glucose. The GI values are classified as low, medium, and high. Below are examples of foods in each category (2):

Low GI (0-55) — old-fashioned oats, apples, peanuts

Medium GI (56-69)— orange juice, instant oatmeal, whole wheat bread

High GI: (70 and higher)— watermelon, baked potato, corn chips

Critics of the GI classification say it is not a measure of good nutrition. For example, the GI of ice cream, a food high in calories and fat, is low; whereas, the GI of watermelon is high even though it is low in calories and a good source of vitamin A.

The Glycemic index only tells part of the story. The glycemic load (GL) concept gives us a more real-life predictor of carbohydrate consumption. The GL considers the glycemic index of a particular food and the amount of glucose a portion will deliver (3). As a frame of reference, a GL higher than 20 is considered high, between 11 and 19 is medium, and ten or less is considered low (4). It is recommended to consume a total GL of 100 or less each day.

Studies on GI and its impact on health-related outcomes have mixed results. The American Diabetes Association states that the overall amount of carbohydrates consumed is more important than GI (5). The glycemic index diet is still debated among dietitians, with this RDN not recommending it. It’s a complex system when carb counting is much easier and effective.

Perhaps a more straightforward way of keeping track of foods that drastically raise your blood sugar is to keep a log. Then you can avoid these foods or modify them. For instance, some people complain that white rice spikes their blood sugar levels. In this case, you have three choices: avoid it, eat a smaller portion, or switch to brown rice.

The bottom line is do what works for you. Maintaining healthy glucose levels and a healthy weight are of utmost importance in diabetes management. Talk to your doctor or dietitian if your blood sugar levels remain high.

Until next time, be healthy!

Dear Dietitian

Leanne McCrate, RDN, LD, CNSC, is an award-winning dietitian based in Missouri. Her mission is to educate consumers on sound, scientifically-based nutrition. Do you have a nutrition question? Email her today at Dear Dietitian does not endorse any products, health programs, or diet plans. References • Venn, B., Green, T. Glycemic index and glycemic load: measurement issues and their effect on diet–disease relationships. Eur J Clin Nutr 61, S122–S131 (2007). • 2,4 Glycemic index and glycemic load (n.d.) Retrieved from • The lowdown on glycemic index and glycemic load (n.d.) • Glycemic index and diabetes (n.d.) diabetes