If you are a diabetic or a dieter that follows a low carbohydrate diet to manage your weight, you may be familiar with the glycemic index. The glycemic index is a the scale that is used to determine what is a "good" carbohydrate and what is a "bad" carbohydrate. Understanding what the glycemic index is and what the rankings mean may help you better achieve your health and fitness goals.
Glycemic Index
The Joslin Diabetes Center and Harvard Medical School explains that the glycemic index is a numerical ranking system indicating the after-meal response your body will have to a specific food or beverage compared to a standard amount of glucose. In more simple terms, the glycemic index is a chart that predicts how much a certain food or drink will raise your blood sugar levels. The higher the number, especially foods that rank 70 and above, the more significantly and rapidly a food elevates your blood sugar. The lower the number, foods that score 55 and below, the less a food effects your blood sugar. Foods that rank between 56 and 69 are thought to have a moderate effect on your blood sugar levels.
What Determines the Glycemic Index?
Sandra Woodruff, Registered and Licensed Dietitian at Florida State University and the Joslin Diabetes Center, explain that several factors determine a food's glycemic index ranking. First, the degree to which the food is processed or refined influences its glycemic index score. Foods that have undergone extensive processing tend to have higher glycemic index rankings. Next, how much dietary fiber a food has is considered in the glycemic index ranking. The more fiber a food has, the lower the glycemic index ranking. Additionally, the type of carbohydrates a food contains is also significant. The more simple sugars a food has, the higher the glycemic index is likely to be. Other factors include, how the food is prepared and how long or if the food is cooked.
High Glycemic vs. Low Glycemic Foods
Foods that score high on the glycemic index include foods made from finely ground flours such as white bread, baked goods, popular commercial breakfast cereals, starchy white potatoes and white rice. Additionally, high-sugar snacking foods such as potato chips, candy and pretzels receive high glycemic scores. Foods that rank below 55 as low glycemic foods include foods made from minimally processed whole grains such as steel cut oats, old-fashioned oatmeal, long-grain brown rice and barley. Moreover, other low glycemic foods include beans, legumes and vegetables, with the exception of potatoes. Fruit although it has sugar is also has a low glycemic food. The sugar in fruit is naturally occurring and not added processed or refined sugar such as in candy bars.
Expert Insight and Considerations
Dr. Jonny Bowden, Ph.D and clinical nutrition specialist, explains that the glycemic index is a useful tool but the ranking system can be deceptive. You may get the impression that a certain food will raise your blood sugar levels when it actually will have no significant effect. This is because the glycemic index does not account for how many carbohydrate a food has per serving. For example, watermelon is considered a high-moderate glycemic food with a ranking of 72, plus or minus 13. Dr. Bowden reports that watermelon is mostly water and will not increase your blood glucose level because it has very few carbohydrates. Dr. Bowden argues that the "glycemic load" is a far better tool for predicting glycemic response because it accounts for the glycemic index and also the quantity of carbohydrates in a food.
References
- "The 150 Healthiest Foods on Earth"; Dr. Jonny Bowden; 2007
- Joslin Diabetes Center: The Glycemic Index and Diabetes
- Florida State University: Glycemic Index; Sandra Woodruff RD, LD. LN.
- Harvard Medical School: Glycemic index and glycemic load for 100+ foods
- Southbeach Diet Plan: Glycemic Index Food Chart
