The glycemic load, or GL, is a tool scientists and dieters use to decipher the impact of foods on blood sugar. The GL ranks the effect of carbohydrates on blood sugar while taking carbohydrate type, such as fiber, into account. According to Harvard School of Public Medicine, foods with a low or medium GL are healthier and less apt to cause diabetes and heart disease later in life.
How It Works
Understanding GL starts with a review of its predecessor, the glycemic index. Glycemic index is a measurement of the carbohydrates impact on blood sugar versus plain sugar, or glucose. High glycemic index numbers mean rapid fluctuations and impact on blood sugar, which can lead to chronic disease when consumed regularly. Conversely, low index foods ranking lower than 55 minimally impact the blood sugar levels and are better digested by the body. GL takes the glycemic index and carbohydrate type -- sugar, fiber, or starch -- into account and applies an associated index rating or number to each carbohydrate type.
Impact
Similar to the glycemic index, the GL index ranges from low to high by categorizing foods physiological impact. The Harvard School of Public Medicine classifies carbohydrate impact according to three levels of low, medium and high. Low GL foods measure less than 10 on the index, medium are from 11 to 19, and high foods rank more than 20, according to the Harvard School of Public Medicine. These numbers, although a good general guide, should not be taken at full face value. The serving sizes on most GL tables are not standard serving sizes, warns the "American Journal of Clinical Nutrition."
High Fiber
Foods high in fiber content, such as vegetables, fruits and legumes, have a low glycemic load. These are the carbohydrates that minimally impact blood sugar, meaning less fluctuation of highs and lows that can lead to decrease satiety, munching needlessly and fatigue. All vegetables are low GL foods with one exception: white potatoes. White potatoes in any form are starchy foods -- basically simple sugars easily digested and thrown into the bloodstream.
Whole Grain
Foods ranking from 11 to 19 are medium GL foods, such as grains and whole grain pastas. These foods will impact the blood sugar level, causing it to rise, but not rapidly. A medium impact GL food can become a high-impact one if serving sizes are ignored or the food is highly processed. For instance, one serving of brown rice is a medium impact food, whereas the refined white rice enters the high impact category.
Starch and Sugar
Starches, sugars and refined wheat products all rank as high GL foods. These products are quickly digested by the body and turned into nothing more than raw sugar. Although a source of instant energy, raw sugar is stored as fat if the intake outweighs the energy expenditure level. White potato products, colas and sugary juices, candy bars and foods from refined flour will have the highest impact on blood, rapidly raising the blood sugar. Sustained elevations in blood sugar can lead to diabetes according to the Harvard School of Public Health.
