The Glycemic Index: What Is It?
Good carbs, bad carbs, here is everything that you need to know about the glycemic index.
The glycemic index is a tool that is commonly used by health professionals and individuals to promote better health, blood sugar management and weight loss. But, exactly what is the glycemic index? And does the glycemic index work? Here is a closer looks at the glycemic index, what it is, how it works, how it can impact your health, and how to use it.
What Is The Glycemic Index?
The glycemic index is a scale that ranks carbohydrate-containing foods and drinks based on how quickly they elevate blood sugar once consumed. Values are associated with foods and beverages, also known as GI values, and are ranked on a scale of 0 to 100, with pure glucose (sugar) given a value of 100. The lower a food is on the GI scale, the less likely it is to affect your blood sugar, while foods with high GI rankings are likely to have a more rapid and impactful effect on blood sugar.
Glycemic Index Rankings
Glycemic index rankings are given to carbohydrate-based foods depending on how quickly or slowly they increase blood sugar levels once consumed. There are three primary categories of GI rankings:
- Low: 55 or less
- Medium: 56 to 69
- High: 70 or more
It is suggested that foods with a low ranking should be chosen most often, foods with a medium ranking should be chosen less often, and foods with a high ranking should be chosen least often.
Although foods, typically, have one GI rating, the actual glycemic index of a food can vary based on ripeness, preparation and storage. For instance, the GI of an under-ripe banana is 30, while the GI of a ripe banana is 51, and the GI of a boiled sweet potato is 46, while the GI of a baked sweet potato is 94.
Glycemic Index of Foods
GI rankings are assigned to foods which contain carbohydrates; fruits, vegetables, grains, beans, lentils, dairy and products made out of them. Therefore, foods that do not contain carbohydrates, such as meat, seafood, poultry, herbs and spices, are not assigned a ranking on the glycemic index list.
Low Glycemic Foods
Foods with a low GI ranking are typically whole foods that are unrefined and include most fruits and vegetables, beans, whole grains, sourdough, sprouted grain bread, pasta and dairy products.
Medium Glycemic Foods
Foods with a medium GI ranking include higher sugar and starch-containing whole foods, such as pineapple and dried fruit, and lightly refined foods such as corn chips, high-fibre cereals, pita bread, couscous, some noodles and crackers.
High Glycemic Foods
Foods with a high GI ranking are typically highly processed and highly refined forms of carbohydrates. These include sugary cereals, baked goods, granola bars, crackers, chips, pretzels, soda and sugar.
Glycemic Index Chart
|LOW GI (55 or LESS)||MEDIUM GI (56-70)||HIGH GI (70 or MORE)|
|sweet potatoes||baby potatoes||baked potatoes, French fries|
|rice||brown rice, basmati rice||instant rice|
|stone-ground flours and products made from them||rye bread, whole wheat bread, pita bread||refined flours and products made from them|
|steel-cut oats||quick oats||instant oats|
|milk, yogurt||ice cream||N/A|
|chickpeas, beans, lentils||bean soups, lentil soups||N/A|
|apples||cantaloupe, dried fruits||juices, sodas|
Glycemic Index List
- Cherries: 22
- Plums: 24
- Grapefruit: 25
- Peach: 28
- Pear: 33
- Apple: 36
- Strawberry: 40
- Raspberry: 41
- Dates: 42
- Orange: 43
- Banana: 51
- Butternut Squash: 51
- Mango: 51
- Blueberries: 53
- Raisins: 54
- Grapes: 56
- Pineapple: 59
- Beets: 64
- Cantaloupe: 65
- Watermelon: 76
- Broccoli: 10
- Cauliflower: 10
- Asparagus: 15
- Cucumber: 15
- Tomato: 15
- Zucchini: 15
- Carrots (boiled): 39
- Butternut Squash (boiled): 51
- Sweet Potato (boiled): 63
- Potato (boiled): 78
- Barley: 28
- Farro: 40
- Buckwheat: 51
- Steel-Cut Oats: 52
- Corn: 52
- Quinoa: 53
- Millet: 54
- Rolled Oats: 55
- Couscous: 65
- Brown Rice: 68
- White Rice: 73
- Pasta: 29
- Wheat Tortilla: 30
- Corn Tortilla: 42
- Sprouted Grain Bread: 53
- Sourdough: 53
- Popcorn: 65
- Crackers (soda): 74
- Whole Wheat Bread: 74
- White Wheat Bread: 75
- Rice Cakes: 82
- Beans: 24
- Chickpeas: 28
- Lentils: 32
Dairy Products & Alternatives:
- Almond Milk: 25
- Coconut Milk: 31
- Soy Milk: 34
- Milk (skim): 37
- Milk (whole): 39
- Yogurt: 41
- Ice Cream: 51
- Oat Milk: 69
- Rice Milk: 86
- Maple Syrup: 54
- Coconut Sugar: 54
- Molasses: 55
- Honey: 61
- Sugar: 65
In general, the more processed a food is, the higher its GI ranking, and the more fiber, protein and fat in a food, the lower its GI ranking. In order to determine the glycemic index of a specific food, you can use a glycemic index calculator like this online database.
Factors that Affect Glycemic Index
Although all carbohydrate-based foods are given a glycemic index ranking, there are a number of factors that can impact the glycemic ranking of foods, such as:
- The Type of Sugar it Contains: Different sugars have different GI rankings and different foods contain different types of sugar. For instance, fructose has a GI of 19, while sucrose has a GI of 65, and maltose has a GI of 105. Therefore, the glycemic index of any given foods depends on the type and amount of sugar it contains.
- The Amount of Starch it Contains: Starch is a form of carbohydrate made up of amylose and amylopectin, and different foods will contain different ratios of these two forms of starch. Food with a higher amount of amylose has been shown to slow the glycemic response of the food. (4)
- The Amount of Fibre it Contains: There are two types of fibre found in food: soluble fibre and insoluble fibre. Insoluble fibre is found mostly in grain products, while soluble fibre is found mostly in fruits, vegetables and legumes, and both types of fibre can help to reduce the glycemic response of a food since fibre helps to slow the digestion and absorption of sugar to the bloodstream.
- How Refined It Is: Processing foods, specifically carbohydrates, can increase the glycemic index of the food or the food they are made from. For instance, steel-cuts oats have a lower GI ranking than instant oats (a more refined version of steel-cut oats).
- Nutrient Composition: The amount of protein and fat found in a food will also impact its glycemic response. A food or meal with a higher ratio of protein and fat will help to reduce the glycemic response to a meal.
- Cooking Method: Generally speaking, the longer / more a food is cooked the higher its GI ranking, as its sugars are broken down and will, therefore, reach the bloodstream faster.
- Ripeness: Similar to the cooking method, the riper a food is (specifically fruits and vegetables) the higher its sugar content. Unripe fruits have a higher starch and lower sugar content, while ripe or over-ripe fruit typically have a lower starch and higher sugar content.
Glycemic Index vs Load
It is also important to note that the glycemic index is different than the glycemic load of food. The glycemic index is a measure of the rate at which a food raises blood sugar once consumed, however, that only tells part of the story. To understand a food’s complete effect on blood sugar, you need to know how quickly it makes sugar (glucose) enter the bloodstream and how much glucose per serving it can deliver. Unfortunately, the glycemic index does not take into account the amount of food that is consumed. Fortunately, the glycemic load of a food does both; it accounts for how much carbohydrate is in the food and how much each gram of carbohydrate in the food raises blood sugar levels.
For example, watermelon has a high glycemic index (80), while an actual serving of watermelon has so little carbohydrate that the glycemic load is only 5. However, if multiple servings of watermelon were consumed at one time, the glycemic load would increase and, therefore, it may have a greater overall impact on blood sugar. It is for this reason, it is important to consider both the glycemic index and glycemic load of food if you are looking to use this tool for health purposes.
Benefits of the Glycemic Index
Individuals looking to improve their diet or those who are at risk from diabetes may find the glycemic index very helpful. In fact, there are many benefits of using the glycemic index as a health tool. (3) A low GI diet has been shown to help:
- Decrease the risk of type 2 diabetes and its complications,
- Decrease the risk of heart disease and stroke,
- Increase satiety or feel full longer,
- Maintain weight or lose weight.
Problems with the Glycemic Index
Although the glycemic index does have some benefits, as a single tool, it also has many drawbacks.
- It does not account for the varying amounts of carbohydrate in different foods.
- It only measures one food at a time. (It does not account for what other foods you are eating.)
- It does not account for the cooking method of foods.
- It does not account for the ripeness of foods.
- It does not account for glycemic load. (It does not account for the serving sizes you actually eat.)
Tips for Following a Low Glycemic Diet
One of the simplest ways to create a low-glycemic meal is to create a well-balanced meal that contains protein, fat and fibre. Not only does this help to ensure that you are opting for low GI foods (that contain fibre), but it helps to ensure that you are building a meal with protein and fat, which have been shown to reduce and mitigate the negative glycemic effect on blood sugar.
In addition to creating well-balanced meals, you can also create meals that contain little if any carbohydrates at all. These foods include:
Here are some sample well-balanced meal ideas that contain low-glycemic carbohydrates, fibre, protein and fat.
- Rolled Oats + Whole Milk + Blueberries + Pumpkin Seeds
- Sprouted Grain Toast + Butter + Eggs
- Omelette (Eggs + Spinach + Tomatoes + Goat Cheese) + Potatoes
- Salad (Mixed Greens + Tomatoes + Cucumber) + Quinoa + Tuna + Avocado + Olive Oil
- Minestrone Soup (Beans + Vegetables) + Sourdough + Butter
- Sprouted Grain Bread + Turkey + Cheese + Lettuce + Tomato
- Shrimp Stir-Fry (Rice + Broccoli + Peppers + Carrots + Shrimp)
- Chicken Thighs + Sweet Potatoes + Asparagus
- Pasta + Tomato Sauce + Ground Beef + Parmesan
The Bottom Line
The glycemic index is a tool that you can use to help make healthier carbohydrate choices, however, it is not the only tool or the best tool. There as several factors that can influence the glycemic rating of food, including ripeness, cooking method, nutrient composition and food combinations. Following the principles of low-glycemic eating and choosing foods that rank low on the glycemic index scale is likely beneficial for some people, specifically individuals with diabetes, however, it is best used in conjunction with other health tools; opting for whole foods, creating balanced meals, and regular activity. When it comes to eating well, everything is about context, volume and frequency. Both low and high glycemic foods can be consumed in a healthy diet when high glycemic foods are consumed in moderation in conjunction with a diet rich in whole foods, fibre, protein and healthy fats.