Glycemic index (GI) is a ranking of carbohydrate containing foods based on their immediate effect on blood glucose (blood sugar) levels. Carbohydrates which break down quickly during digestion have the highest glycemic indexes. The blood glucose response to these carbohydrates is fast and high. Carbohydrates which break down slowly, releasing glucose gradually into the blood stream, have low glycemic indexes. The GI of glucose is 100 and everything else is compared to this. Although each food is given just one number its GI can actually vary depending on variety, ripeness, cooking method and length of storage.
While each food has a GI ranking, glycemic load (GL) takes into account the quantity that is eaten by factoring in the amount of carbohydrate in a typical serving. For example, watermelon has a high GI, but an average serving does not contain much carbohydrate (it is mostly water) so it has a low glycemic load. For a serving of food, a GL greater than 20 is considered to be high, 11 to 19 is medium and 10 and below is low. GL is defined as the grams of available carbohydrate in the food x the food’s GI/100.
The Diet/Insulin Connection
Insulin is a hormone that responds directly to what you eat. Among its many roles in the body, insulin regulates fat metabolism and controls blood sugar levels. In an optimal state, the body maintains the blood sugar level in a fairly narrow range: not too low (hypoglycemia) and not too high (hyperglycemia).
Choosing low GI and GL foods means a smaller rise in blood glucose after meals. These foods can keep you feeling fuller longer and can improve the body’s sensitivity to insulin. They can also help people lose weight.
Eating a low GI or low GL diet has been found to be beneficial not only for diabetes and weight loss but also metabolic syndrome, insulin resistance, heart disease and cholesterol. Eating high GI foods has been linked to obesity.
As a general rule, if you eat a varied diet trying to stick mostly with low to medium GL foods you will have the best results.
If you have questions about GI or GL, contact your local naturopathic doctor.