What is the glycemic index?
The glycemic index (GI) is a scale used to quantify the glycemic responses of different carbohydrate-containing foods. The GI can be used to support individuals in making informed food choices, especially individuals with diabetes.
The GI lists foods according to how rapidly it increases blood glucose 2 hours after consuming a portion of that food which contains 25-50 grams of carbohydrates compared to a standard portion of white bread or glucose. Different carbohydrate-containing foods have different effects on blood glucose levels and the GI is a helpful tool when trying to stabilize blood glucose.1
How are GI values determined?
Blood samples of subjects are taken fasting (i.e. without having consumed any food) and at 30-minute intervals for 2-3 hours after the ingestion of a particular food.1
What factors affect the body’s glycemic responses to food?
- The presence of viscous fibres
- The presence of fat and protein
- The ratio of amylose to amylopectin in food
- Cooking and processing
- Food particle size
- Ripeness and food storage
The ripeness of a food can have a large impact on the body’s glycemic response. For example, green, unripe bananas have a low GI value, whereas brown or spotty bananas have a high GI value.2
How is the GI interpreted?
When reading the GI, foods ranked lower on the GI results in lower postprandial (post-meal) glucose levels and a lower insulin response compared to high GI foods.1
What are examples of low GI foods?
Low GI foods have a GI value of 55 or less and are recommended by Diabetes Canada as foods you should choose the most often.
- Heavy mixed grain breads
- Whole grain tortillas
- Sourdough bread
- Steel cut oats
- Pasta – cooked al dente or firm
- Sweet potato
- Unsweetened almond milk
- Cow’s milk
- Greek yogurt
- Regular yogurt
- Kidney beans
- Split peas2
What are examples of medium GI foods?
Medium GI foods are foods with a GI value of 56 – 69 and are recommended by Diabetes Canada as foods to choose less often.
- Pita bread
- Rye bread
- Whole grain wheat bread
- Instant, large flake, or quick oats
- Basmati, brown, short or long grain white rice
- Rice noodles
- Cooled white or red potatoes
What are examples of high GI foods?
High GI foods are foods with a GI value of 70 or more and are recommended by Diabetes Canada as foods to choose the least often.
- White or whole wheat bread
- White or whole wheat naan
- Corn flakes cereal
- Rice Krispies cereal
- Special K cereal
- Jasmine, sticky, and instant white rice
- Hot white or red potatoes
- Rice cakes
- Unsweetened rice milk2
*these are not exhaustive lists of foods on the GI
Can eating a low GI diet help in weight loss?
The consumption of foods with a higher GI results in a greater increase in blood glucose and therefore insulin levels. Insulin promotes fat synthesis, therefore eating a lower GI diet could assist with weight loss because it lowers insulin levels.
- Diabetes – Glycemic Index Background. (2013 July 11). Retrieved from https://www-pennutrition-com.subzero.lib.uoguelph.ca/KnowledgePathway.aspx?kpid=3876&trid=19848&trcatid=38
- Diabetes Canada. (2013). Glycemic Index Food Guide. Retrieved from https://www.diabetes.ca/DiabetesCanadaWebsite/media/Managing-My-Diabetes/Tools%20and%20Resources/glycemic-index-food-guide.pdf
- O’Brien, Laura. (n.d.) Weight/Obesity – Dietary Approaches. Retrieved from https://www-pennutrition-com.subzero.lib.uoguelph.ca/KnowledgePathway.aspx?kpid=15329&pqcatid=146&pqid=23354