The glycemic index and glycemic load are concepts that were developed to help you better understand the quality of the carbohydrates in the food you eat. Fats are categorized according to their degree of saturation and classified as being trans, saturated or unsaturated. Proteins can be evaluated depending on the number of amino acids they provide, making them complete or incomplete proteins. Carbohydrates used to be referred to as simple or complex carbohydrates, but this concept has been replaced with the glycemic index, or GI, and glycemic load, or GL, which depict more accurately how they influence your health.
Carbohydrates
Carbohydrates are present in an abundance of foods and constitute the main source of calories, about 45 to 65 percent , consumed in the standard American diet, according to the 2010 Dietary Guidelines for Americans. Carbs include sugar, starches and fiber and have the role of providing your body with the energy it requires. This nutrient is found in grains, whether refined or whole, legumes, fruits, starchy vegetables, milk, yogurt, sweetened beverages, sweets and desserts.
Glycemic Index
Because not all carbs are the same and classifying them as simple or complex according to the length of their molecules is not adequate, the glycemic index was created in the early 1980s. The objective was to rank carbohydrate-containing foods according to how quickly they contribute to elevating your blood sugar levels after eating. It is measured with a serving of food providing the equivalent of 50 g of carbohydrates. A GI below 55 is low, between 56 and 59 is medium and above 70 is high. Low GI foods have a smoother effect on your blood sugar levels, while high GI foods cause a sharp rise in your blood sugar levels, which can lead to a blood sugar crash within a few hours, according to GlycemicIndex.com.
Glycemic Load
The glycemic load is an extension of the glycemic index concept, but in addition to taking into account the quality of the carbohydrate, it also considers the amount of carbohydrates per serving of food. The GL is the product of the GI of a food and its carbohydrate content per serving. A GL below 10 is low, between 11 and 19 is medium and above 20 is high. The glycemic load is therefore a good tool to evaluate how your blood sugar levels will be influenced by a food. A low GL will help you keep your blood sugar levels more stable, while a high GL will bring your blood sugar levels on a roller coaster of highs and lows, according to the "American Journal of Clinical Nutrition."
Importance for Health
The GI and GL can help you choose healthier carbohydrate-containing foods. Healthier carbs are those with a low glycemic index and load and they help you keep your blood sugar levels more stable over time after eating. A diet rich in low GI foods is associated with a healthier body weight, better blood cholesterol levels and improved blood sugar control for diabetes. A low dietary GL can also benefit your health by preventing or delaying the development of type 2 diabetes, cardiovascular diseases and certain cancers.
Whole vs. Processed Foods
While the GI and GL of a food can help you assess how healthy a carbohydrate-rich food is, you can have a good idea without having to look up the GI and GL values of a food. Generally, less processed foods have a lower GI and GL, whether it is whole grains, legumes, fruits and nonstarchy vegetables. Processed foods, such as breakfast cereals, granola bars, muffins, white bread, white bagels, soft drinks and desserts, tend to have higher GI and GL values. Although the GI and GL are useful and important concepts, your common sense can also be your guide toward the healthiest carbs.
References
- Harvard School of Public Health: Carbohydrates: Good Carbs Guide the Way
- Mendosa: Glycemic Index and Glycemic Load
- University of Sydney: The Glycemic Index
- "American Journal of Clinical Nutrition"; International Table of Glycemic Index and Glycemic Load Values; Kaye Foster-Powell, et al.; 2002
- U.S. Department of Agriculture and U.S. Department of Health and Human Services: 2010 Dietary Guidelines for Americans
