Overview
The glycemic index categorizes foods according to their effect on blood glucose levels within 2 hours of consumption. Foods with a high glycemic index contain carbohydrates that break down quickly and tend to raise glucose levels higher and faster than low glycemic index foods. Dietitians typically refer to low glycemic foods as “best” choices.
Benefits
A desirable low glycemic response consists of a slow rate of absorption followed by a modest rise in blood glucose that smoothly returns to normal. In contrast, an undesirable high glycemic response involves fast absorption that surges blood glucose, causing an overreaction by the body that suddenly plunges glucose below normal. According to the Mayo Clinic, knowing the glycemic index of foods could potentially help regulate blood sugar at a lower level and possibly even reduce diabetes medications.
Problems
The Mayo Clinic cautions that the glycemic index refers to single food items, but people eat foods in combinations that affect blood sugar differently. The glycemic index does not take food preparation methods or quantities into account and only includes foods that contain carbohydrate. The glycemic index does not consider nutrient content so a food with a low glycemic index may be high in calories, sugar or fat.
Representative Foods
Typical high glycemic index foods include white bread, short-grain rice, potatoes, carrots, watermelon, jelly beans, soft drinks and honey. Moderate glycemic index foods include rye bead, banana, pineapple, orange juice and ice cream. Low glycemic index foods include pumpernickel bread, pasta, soy, lentils, beans, peaches, apples, oranges, milk, yogurt and chocolate.
Affect on Diabetes
The American Diabetes Association reports that the stronger predictor of blood glucose is total carbohydrate in food rather than glycemic index. Most people with diabetes do best with carbohydrate counting and still need to balance carbohydrate intake with physical activity and prescribed insulin. If willing to expend additional effort, though, people with diabetes may fine-tune their blood glucose management by also considering the glycemic index of foods.
Considerations
Controversy surrounds the practical application of the glycemic index. Those in favor point out that a low glycemic diet may help prevent obesity, heart disease and diabetes. Those opposed argue that the concept is complicated and sometimes counterintuitive. For instance, ice cream has a lower glycemic index than watermelon, but watermelon contains less carbohydrate per serving. Some candy bars have a low glycemic index but definitely do not qualify as health food.
Because of apparent contradictions, an incomplete list of indexed foods and food labels that do not include the index, glycemic index does not provide a straightforward and easy-to-use tool. So scientists introduced the idea of glycemic load to account for both quality and quantity of carbohydrate in food. In the July 2002 issue of the “American Journal of Clinical Nutrition,” Kaye Foster-Powell, Susanna Holt and Janette Brand-Miller published an International Table of Glycemic Index and Glycemic Load.
About this Author
Norma DeVault, a registered dietitian, has been writing health-related articles since 2006. Her articles have appeared in the “Journal of the American Dietetic Association.” She holds a Doctor of Philosophy in human environmental sciences from Oklahoma State University and a Master of Business Administration from the University of Tulsa.
