Glycemic load
The glycemic load (GL) is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) and the portion size. Glycemic load or GL combines both the quality and quantity of carbohydrate in one ‘number’. It’s the best way to predict blood glucose values of different types and amounts of food. The formula is: GL = (GI x the amount of available carbohydrate) divided by 100. [1]
The usefulness of glycemic load is based on the idea that a high glycemic index food consumed in small quantities would give the same effect as larger quantities of a low glycemic index food on blood sugar. Glycemic Load is the product of the Glycemic Index and the grams of available carbohydrate (GL = GI × available Carb grams). For example, white rice has a somewhat high GI, so eating 50g of white rice at one sitting would give a particular glucose curve in the blood, while 25g would give the same curve but half the height. Since the peak height is probably the most important parameter for diabetes control, multiplying the amount of carbohydrates in a food serving by the glycemic index gives an idea of how much effect an actual portion of food has on blood sugar level.
One recent study has questioned the value of using glycemic load as a basis for weight loss programmes.[2]
Glycemic load appears to be beneficial in dietary programmes targeting metabolic syndrome, insulin resistance, and weight loss; Studies have shown that sustained spikes in blood sugar and insulin levels may lead to increased diabetes risk.[3] The Shanghai Women's Health Study concluded that women whose diets had the highest glycemic index were 21 percent more likely to develop type 2 diabetes than women whose diets had the lowest glycemic index.[4] Similar findings were reported in the Black Women's Health Study.[5] A diet programme that manages the glycemic load aims to avoid sustained blood sugar spikes, and can help avoid onset of type 2 diabetes.[6] For diabetics, glycemic load is a highly recommended tool for managing blood sugar.
Glycemic load for a single serving of a food can be calculated as the quantity (in grams) of its carbohydrate content, multiplied by its GI, and divided by 100. For example, a 100g slice serving of watermelon with a GI of 72 and a carbohydrate content of 5g (it contains a lot of water) makes the calculation 5·72/100=3.6, so the GL is 3.6. A food with a GI of 100 and a carbohydrate content of 10g has a GL of 10 (10·100/100=10), while a food with 100g carbohydrate and a GI of just 10 also has a GL of 10 (100·10/100=10).
Data on GI and GL comes from the University of Sydney (Human Nutrition Unit) GI database at [6] through [7].
The GI was invented in 1981 by Dr Thomas Wolever and Dr David Jenkins at the University of Toronto and is a measure of how quickly a food containing 25 or 50 grams of carbohydrate raises blood glucose levels. Because some foods typically have a low carbohydrate content, Harvard researchers created the GL, that takes into account the amount of carbohydrates in a given serving of a food, and so provides a more useful measure. Glycemic Load also has a scale. Low is 10 or less, Medium is 11-19 and 20 or greater is considered High.
List of foods and their glycemic load, per 100g serving
All numeric values provided in the table are approximate.
| Food | Glycemic index | Carbohydrate content (by weight) |
Glycemic Load | Insulin index[7][8][9] |
|---|---|---|---|---|
| Baguette, white, plain (France) | 95 | 50% | 48.0 | — |
| Banana, Mean of 10 studies | 52 | 20% | 10.0 | 81 |
| Carrots, Mean of 4 studies | 47 | 7.5% | 3.5 | — |
| Corn tortilla (Mexican) | 52 | 48% | 25.0 | — |
| Potato, Mean of 5 studies | 50 | 19% | 9.3 | 121 |
| Rice, boiled white, mean of 12 studies | 64 | 24% | 15.4 | 79 |
| Watermelon | 72 | 5% | 3.6 | — |
See also
External links
- Glycemic index website and official GI database - University of Sydney
- "International table of glycemic index and glycemic load values: 2002", American Journal of Clinical Nutrition
- Tree/freetext search-style database of Glycemic Index and Glycemic Load (same number of food items but also calculates totals according to FAO/WHO specifications).
- Low glycemic index recipes, cooking tips, and food lists Glycemic Gourmet
References
- ^ The Glycemic Index FAQs: What is the difference between glycemic index (GI) and glycemic load (GL)?[1]
- ^ Das et al. conducted a study on 36 healthy, overweight adults, using a randomised test to measure the efficacy of two diets, one with a high glycemic load and one with a low GL. The study concluded that there is no statistically significant difference between the outcome of the two diets. However, this might simply be due to the small sample size (n=36). In the study, the low GL diet did provide the most weight loss on average, but not enough to clear the bar of "statistical significance". See Das et al. (2007). "Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial" American Journal of Clinical Nutrition, Vol. 85, No. 4, 1023-1030[2]
- ^ Ludwig DS. The glycemic index: physiological mechanisms relating to obesity, diabetes, and cardiovascular disease. JAMA[3]. 2002; 287:2414-23
- ^ Villegas R, Liu S, Gao Y-T, et al. Prospective Study of Dietary Carbohydrates, Glycemic Index, Glycemic Load, and Incidence of Type 2 Diabetes Mellitus in Middle-aged Chinese Women. Arch Intern Med[4]. 2007; 167:2310-2316.
- ^ Krishnan S, Rosenberg L, Singer M, et al. Glycemic Index, Glycemic Load, and Cereal Fiber Intake and Risk of Type 2 Diabetes in US Black Women. Arch Intern Med. 2007; 167:2304-2309.
- ^ Harvard School of Public Health: The Nutrition Source: Simple Steps to Preventing Diabetes [5]
- ^ ""Insulin Index" By David Mendosa".
- ^ ""Natural Eating Newsletter"".
- ^ ""Rice: a high or low glycemic index food" by Janette Brand Miller, Edna Pang, and Lindsay Brainall" (PDF).