Many dieticians and health/diet-conscious Americans alike use a food’s Glycemic Index (GI) score as a reference point for ensuring their diabetes or cardiovascular disease risk is under control through their food choices. Previous versions of the International Tables of Glycemic Index were published in 1995, 2002, and 2008, but between 2008 and 2021 there has been no update.
However as Fiona Atkinson et al. detail in a recently-published paper at the American Journal of Clinical Nutrition, the number of studies conducted between that period containing the terms “Glycemic Index,” or “Glycemic Load” in the title, index, or abstract, has tripled from 2,500 to 7,500.
With so much new information, Atkinson’s team wanted to take the opportunity to update the index on their own, introducing new concepts to answer old questions which the GI struggles with.
“Are there new GI values for foods or varieties?” the authors write. “Are there additional measurements of foods that have been tested previously and, if so, are there any time-related changes in regard to staples such as bread or rice, which have been repeatedly measured over the years? Finally, are there any national/regional differences within certain food groups, such as bread, rice, or potatoes?”
In addition to all the new information, the International Standards Organization (ISO) updated the measuring of foods to more accurately detail a food’s GI score, while an interlaboratory study assessed six different foods across three different labs in three different countries and found no difference in reported GI scores.
The most significant advancement in terms of accessible knowledge must be the range of preparations included in the new GI. The authors took into account studies (sometimes many) which looked at how traditional cultures’ preparation of a food item may change its GI score, for example the white rice in sushi has a different GI score than white rice prepared by other means, by the addition of vinegar, sugar, and refrigeration.
The Glycemic Index 2021
In the new index, available for download from the study paper, the researchers included close to double the number of food items compared to the 2008 one, as well as significantly more preparation methods and food varieties.
Supplemental Table 1 includes only the entries researched according to the ISO standard, and the glycemic load (GL) was measured after being consumed by more than 10 separate adults with totally normal glucose tolerances.
The level of detail is exquisite, and can help even the most curious of meal planners plug in exactly what they’re looking for, as not only are cooking methods, geographical varieties, and packaging taken into account, but name brands as well.
There are 24 entries for white rice, which like many of the entries, varies wildly within categories for GL score. Potatoes for example spanned 84 (out of 100) for instant mashed potatoes to 49 for cooked potatoes that were refrigerated overnight.
Most foods such as fruit, dairy, nuts, vegetables, legumes, and pasta tended to be remarkably similar around the globe. Breads, cereals, potatoes, and other carb-heavy stables tended to go in the opposite direction and had strong variation.
“One of the most important differences between the 2008 and 2021 editions of the tables is the use of a standardized carbohydrate portion to calculate GL values in the current edition,” write the authors. “This approach was chosen because typical serving sizes (necessary to calculate the GL) vary widely from product to product, as well as country to country”.