Carbohydrates constitute a big part of the American diet. According to the 2010 Dietary Guidelines for Americans, 45 to 65 percent of your daily calorie intake should come from carbohydrates. Since carbohydrates provide approximately half of your daily calories, it is important to select the best types of carbohydrates to provide your body with the nutrients it needs. The glycemic index, or GI, as well as the glycemic load, or GL, are good tools to determine whether the carbohydrates you choose are good choices for your health.
Glycemic Index Overview
The GI was created in the 1980s at the University of Toronto to help people with diabetes better estimate how carbohydrate-containing foods affect blood sugar levels. The GI ranks carbohydrates on a scale of 0 to 100. Values below 55 are low, between 56 and 69 are medium, and above 70 are high. Low GI foods result in a smaller increase in your blood sugar levels, while high GI foods quickly result in a sharp rise in your blood sugar concentrations.
Glycemic Index Recommendations
Lowering your dietary GI is associated with a healthier body weight, more stable blood sugar levels and improved blood cholesterol levels. Make most of your carbohydrate foods low GI choices and replace high GI carbohydrates with lower GI alternatives. For example, avoid high GI potatoes, white rice, white bread, refined grains and baked goods, pretzels, rice cakes, candies and desserts. Instead, opt for low GI carbohydrates, such as sourdough bread, baked goods prepared with stone-ground whole grain flour, beans, lentils, whole grain pasta, Basmati rice, quinoa, old-fashioned oatmeal and fruits. Foods that are free or almost free of carbohydrates, such as some vegetables, meat, fish, poultry, cheese and eggs, do not have an assigned GI value but it can be estimated to be zero.
Glycemic Load Overview
The GL is based on the GI concept but also incorporates a quantitative notion. While the GI gives you an idea of the quality of a carbohydrate-containing food, the GL corresponds to both the amount and type of carbohydrate eaten. The GL was developed at Harvard University in the late 1990s as a more comprehensive way to assess the value of the carbohydrates you include in your diet. The GL of a food is calculated by multiplying its carbohydrate content per serving with its GI, divided by 100. GL values of 10 and below are considered low, between 11 and 19 are medium and above 20 are high.
Glycemic Load Recommendations
Because a high dietary GL is associated with an elevated risk of developing cardiovascular disease, type 2 diabetes and some types of cancers, it is preferable to keep your GL low. You can achieve a low GL by replacing high GI foods with either low GI alternatives or larger amounts of protein or healthy fat. For example, instead of high GI mashed potatoes at dinner, you can serve quinoa, which is a lower GI carbohydrate, or simply serve more generous amounts of protein from fish, poultry or meat, or add more fat from avocado, olive oil, nuts or seeds.
References
- 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
- Harvard School of Public Health: Carbohydrates: Good Carbs Guide the Way
- U.S. Department of Agriculture and U.S. Department of Health and Human Services: 2010 Dietary Guidelines for Americans
