The glycemic index is a ranking scale and system that can be useful if you need to keep your blood glucose levels stable. Diabetics and dieters who need to keep their blood sugar levels under control can particularly benefit from understanding what the glycemic index is and how to interpret the scale. Consult your doctor, especially if you are diabetic, before making significant changes to your diet or lifestyle.
General Information
If you have never seen a glycemic index chart, it may seem complicated. The glycemic index is merely a numerical ranking system that scores foods and drinks on how they will likely affect your blood sugar levels. Most glycemic index charts only list carbohydrate-based foods because carbohydrates have the greatest effect on your blood sugar levels. In general, foods that score between 0 and 55 are considered low glycemic foods that will not have a very significant effect on your blood glucose levels. Foods that score between 56 and 69 have a moderate effect on your blood sugar levels. Foods that score above 70 will have a significant effect on your blood sugar.
High Glycemic Foods
Sandra Woodruff, Registered Dietitian at Florida State University explains that it is not simply the amount of sugar or the amount of carbohydrates that a food contains that determines its glycemic ranking. It is also how the food is made and the type of sugars or carbohydrates it contains. High glycemic foods tend to undergo a lot of processing and refinement. Foods such as breads and baked goods made from finely ground flour and with added sugars, processed high-sugar breakfast cereals, starchy white potatoes and short-grain rice are high glycemic foods. White baguettes, corn flakes, commercially-made fruit snacks and pretzels all rank very high on the glycemic index.
Low Glycemic Foods
Foods that rank low on the glycemic index are carbohydrate sources that have the opposite characteristics of high glycemic foods. Low glycemic foods tend to be minimally processed and refined. Low glycemic foods also tend to have moderate or high amounts of dietary fiber that slows down how fast your body absorbs sugar. If these foods have sugar, the sugar is naturally occurring and not in the form of added sweeteners that can raise your blood sugar. A good example is fruit. Although fruit has sugar, it is generally a low glycemic food because it does not have added sugars. Most vegetables, fruits, legumes, skim milk and whole grain foods have low glycemic index rankings.
Expert Insight
Dr. Jonny Bowden, Ph.D and Clinical Nutrition Specialist, explains that the glycemic index is helpful but also has its limitations. Dr. Bowden reports that certain foods such as carrots and watermelon receive high glycemic scores but will not raise your blood sugar levels significantly if you eat them. This is because the glycemic index does not account for the amount of carbohydrates a food has per serving. Watermelon, despite a glycemic index score of 72 plus or minus 13, will not raise your blood sugar levels because it is mainly made of water, air and a moderate amount of fiber. Dr. Bowden states that the "glycemic load" is a far better predictor of after-meal glucose response because it accounts for the glycemic index and the number of carbohydrates a food has.
References
- "The 150 Healthiest Foods on Earth"; Dr. Jonny Bowden; 2007
- E-International Science Research Journal: A Study of Glycemic Index of Ten Fruits; Dr.M.Premanath, et. al
- Florida State University: Glycemic Index; Sandra Woodruff RD, LD. LN.
- Joslin Diabetes Center: Insulin Action
- Joslin Diabetes Center: The Glycemic Index and Diabetes
- Harvard Medical School: Glycemic index and glycemic load for 100+ foods
