Understanding Food Labels and the Glycemic Index

It does not matter whether you have diabetes or not, it is always important to read and understand food labels if you want to know the real contents of the food you are eating and not just what the front of the label says. If you do have diabetes, it is also essential that you learn about and understand the glycemic index (GI). Understanding food content and the glycemic index is one of the most important steps you can to take in the control of blood sugar levels.

What is Food Labeling?

Food labeling is a standardized practice in which the food product manufacturer is required to list specific information on explicit nutrients and nutritional content.[1]

One of the outcomes of rationing during World War II was food labels. The circumstances of war forced a re-evaluation of the food system. For the first time in history it was required that the contents of boxes and cans be labeled. Originally, this was done in a manner that primarily reflected the actual food content. This became transmuted into food value over time like the listing of daily required amounts of particular vitamins satisfied by consuming a serving of the food. During the development of the process, a new system of reporting on food content was devised. It was accompanied, of course, by specific terminology currently applied by nutritionists and other individual specialists in the field. Common terms include the following:

  • Reference Daily Intake or Recommended Daily Intake (RDI) – This is translated as the amount considered sufficient for the requirements of 98% of all people included in the United States demographics
  • Daily Value (DV) – derived from the RDI and printed on all American and Canadian labels
  • Recommended Dietary Allowance (RDA) – This is an older term on which the RDI was based

The Nutrition Facts Label

When you look at the food label you can see it is separated into specific parts.[2] These sections usually include the following:[3]

  • Serving size – This is a measurement deliberately standardized to domestic measures. It is thus described as a cup or a piece, but it can also be given in weight. The serving size is usually given in American measuring units as well as the metric equivalent.
  • Calories per serving The label provides you with the total amount of calories per serving. It also separately provides the proportion of calories derived from fat. The package label usually stresses that the quantity of calories given is not the content of the entire package but only that of each serving.
  • Nutrient information: This aspect of the label includes the total amount for each of several ingredients. These generally include fat, protein, cholesterol, total carbohydrates (simple and complex), sodium and certain vitamins/minerals e.g. vitamin C

It is required that a label on food packaging must provide you with this specific information. Also reported for each nutritional element is the percentage of daily value (PDV) of per serving.

PDV is located in a footnote to the label. It explains that the amount of two thousand (2,000) calories per day acts as the guideline. The PDV of the nutrients is then subdivided into two specific groups: one that is limited and one that is described as “should get enough.” These consist of vitamins and micronutrients. Prominent among the limited PDVs are the following:

  • Total fat
  • Saturated fat
  • Trans-fat
  • Cholesterol
  •  Sodium

The actual weight, as well as PDV, is listed for both categories.

Where the actual label fails is in its lack of addressing different aspects of life requirements. The measurements are generalized to accommodate as many people as possible. Therefore, they do not consider the changing requirements needed to accommodate age, underlying health and specific stage of life or medical conditions.

What is the Glycemic Index?

A rapid rise in glucose may not be desirable because it stimulates insulin formation and its prolonged release with the resulting effect of lowering the blood sugar, even below the desirable level, resulting in hypoglycemia. In order to have some idea of when eating certain foods will cause this action, researchers and nutritionists came up with the GI. Its intent is to provide guidelines to users on how quickly food is absorbed.

The GI is the measure of the effect of consuming any particular food on the level of glucose in the bloodstream. It is based on a pure glucose rate of 100. All other substances are rated in comparison to the rating of glucose. As a result, you have food that is high, low or somewhere in between.

If the food rates a GI of 70, it is generally considered high. Food that is the most desirable food for a diabetic will register a modest GI found somewhere in the range of 50 to 60. Understanding this system and what food falls into what category is of importance for diabetics. It can assist them in control of their blood glucose levels.[4]

Yet, you may be surprised by the GI of some foods. While foods high in fiber are generally found to have a low GI, it can be very disconcerting to discover that the GI of some chocolate bars is actually lower than that of a bowl of some cereals. Helping to address this situation is the concept of the glycemic load.

What is the Glycemic Load?

The glycemic load takes the glycemic index and carbohydrate content in a pre-determined serving size or quantity of a food item into consideration.[5] For example, consider a watermelon or a cantaloupe. Both register high on the GI. However, eating these foods does not have much effect on the blood glucose level because they are low carbohydrate foods. As a result, you need to look at the glycemic load in addition to the GI. This measurement of carbohydrate consumption can be summarized accordingly:

  • 10 is a low glycemic load
  • 11 to 19 is a medium glycemic load
  • 20 and more is a high glycemic load


Eating healthy should be the goal of every individual, but for diabetics that means eating foods that don’t raise blood sugar levels too high. If you are diabetic, you need to ensure you are eating properly by paying closer attention to the food labels, and the glycemic index and glycemic load of foods for guidance. These are tools that can help you effectively manage your blood sugar levels.


[1] Neporent, L. and Schlosberg, S. (2005). The Fat-Free Truth. Boston: Houghton Mifflin Company.

[2] FDA (2011). “How to Understand and Use the Nutrition’s Fact Label.” Retrieved from http://www.fda.gov/food/labelingnutrition/consumerinformation/ucm078889.htm.

[3] Masharani, U (2008). Diabetes DeMYSTiFieD. New York: McGraw Hill.

[4] Meltzer, SJ; and Belton, AB (2009). Diabetes in Adults. Toronto: Key Porter Books

[5] Stanley, K (2009). 50 Things You Need To Know About Diabetes. Alexandria, VA: ADA.

This article was originally published July 12, 2012 and last revision and update of it was 9/10/2015.