Background

The glycemic index (GI) is a numerical index that ranks carbohydrates based on their rate of glycemic response (i.e. their conversion to glucose within the human body). Glycemic index uses a scale of 0 to 100, with higher values given to foods that cause the most rapid rise in blood sugar. Pure glucose serves as a reference point and is given a GI of 100.

GI values are determined experimentally by feeding human test subjects a fixed portion of the food (after an overnight fast) and subsequently extracting and measuring samples of their blood at specific intervals of time.

The low glycemic index diet involves consumption of foods with low GI. There are several limitations of this diet. There is a scarcity of GI data, with only five percent of the foods having GI values. There is a wide variation in GI measurements. For example, baked Russet potatoes have been tested with a GI as low as 56 and as high as 111. GI values can be affected by preparation method and by combination with other foods. Also, variation may occur due to individual differences in glycemic response.

Another limitation of the GI diet is that the reference food used to determine the glycemic index, white bread, is popular only within a particular culture. The GI diet may not be applicable to different cultures and to people who eat at least 50 grams of carbohydrates per day.

Finally, information about the GI diet available on the internet may be promoting a product. Consumers should critically evaluate the bias of information about the GI diet readily available on the internet and note that the GI diet is not approved by the U.S. Department of Agriculture (USDA).

People use this for...

Safety Safety definitions

Pregnancy And Lactation: There is insufficient reliable evidence about the safety of the low glycemic index diet in pregnancy and lactation. There is no reason to expect safety issues.

Effectiveness Effectiveness definitions

INSUFFICIENT RELIABLE EVIDENCE TO RATE

Diabetes. Preliminary research suggests that low GI diets may reduce glucose levels, insulin levels, and insulin resistance in people with type 1 and type 2 diabetes.

More evidence is needed to rate the low glycemic index diet for this use.

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

Dosing & administration

Adverse effects

Interactions with pharmaceuticals

None known.

Interactions with herbs & supplements

None known.

Interactions with foods

None known.

Interactions with lab tests

Interactions with diseases

Mechanism of action

Foods with a high GI are those that are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels.

Foods that cause a large and rapid glycemic response or that have a high glycemic index will elevate energy and mood initially, but will also release an excess amount of insulin which will sharply reduce blood sugar. Therefore, theoretically, these foods may lead to a cycle of increased fat storage, lethargy, and hunger. Consuming low glycemic index foods theoretically will minimize insulin-related problems by identifying and avoiding foods that have the greatest effect on blood sugar.