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Glycemic Index

Overview

 

If you have diabetes or prediabetes, you likely know all too well the importance of watching your blood sugar levels and being intentional about what you eat. That’s where the glycemic index can come in handy, as it assigns foods a number between 0 and 100, indicating its potential effect on blood sugar levels.

However, while helpful, the glycemic index provides a limited look at just one factor affecting blood sugar.

Learn more about the glycemic index below, which foods tend to cause a spike in blood sugar (or not) and the limitations of this measurement.

What Is the Glycemic Index?

 

The glycemic index measures how quickly foods that contain carbohydrates can increase your blood sugar. The scale is 0 to 100.

Foods can fall into one of three categories:

  • Low: 55 and below
  • Moderate: 56 to 75
  • High: 76 and above

Foods with a low GI typically release sugar slowly when consumed, causing a slower increase in blood sugar. Foods with a high GI release glucose more rapidly and cause a quick increase in blood sugar levels.

A slow and steady increase in blood sugar, compared to rapid increases and drops, also reduces sugar cravings, supports hormonal balance and helps prevent conditions like cardiovascular disease and type 2 diabetes.

Essentially, the glycemic index shows that not everything that contains the exact same amount of grams of carbs will behave the same way in your body. You can measure how your body responds to a cup of orange juice versus how it reacts to other food items: a banana, 25 grams of candy or 25 grams of whole-grain bread.

The reason for these differences comes from how carbs react in your body. Simple carbohydrates — say, the sugars found in soda and sweet desserts — are broken down faster than the more complex carbohydrates found in some vegetables and whole-grain foods. As a result, your blood sugar spikes and then falls rapidly. Over time, doctors believe these constant surges and retreats play a part in people becoming insulin resistant.

 

Glycemic Index vs. Glycemic Load

 

To counteract some of the issues with glycemic index, researchers developed the glycemic load (GL) measurement. Unlike GI, GL accounts for the quantity of the food being eaten.5 The main difference between GI and GL is:

  • Glycemic index is based on eating 50 grams of a specific food
  • Glycemic load is based on eating a standard serving size of a specific food

Glycemic load is calculated by multiplying the GI value by the number of carbohydrates (in grams) per serving, then dividing that number by 100.

 

What is Glycemic Load?

 

The glycemic load (GL) is a more accurate tool for assessing the impact of eating carbohydrates. It gives a more complete picture than does glycemic index alone, because it accounts for the amount of carbohydrate in a serving. A GI value indicates only how rapidly a particular carbohydrate turns into sugar, whereas GL accounts for how much of that carbohydrate a person would typically eat. The carbohydrate in watermelon, for example, has a high GI. However, there is not a lot of sugar in a serving of watermelon, since most of it is fiber and water. Thus watermelon’s glycemic load is relatively low.

Foods that have a low GL almost always have a low GI. In contrast, foods with an intermediate or high GL can have a GI that ranges from very low to very high.

Glycemic Load Range
Low 0 - 10
Medium 11 - 19
High 20 & over

 

Glycemic Load Chart for Common Foods

The following charts highlight low, medium, and high GL foods based on data from the Linus Pauling Institute at Oregon State University.

 

Low-GL Foods (10 or less)
Foods GL
Apple  6
Carrots, boiled  1
Cashews  2
Kidney beans  8
Lentils, dried and boiled  7
Orange  5
Peanuts  1
Pear  4
Skim milk  4
Watermelon  8
White bread (wheat) 10

 

Medium-GL Foods (11 to 19)
Foods GL
Banana 13
Pearled barley, boiled 11
Puffed rice cake 17
Spaghetti, whole wheat 14

 

High-GL Foods (20 or more)
Foods GL
Brown rice   20
Cornflakes 20
Dates 25
Potato, boiled 25
Spaghetti  20
White Rice 35

 

Why Are These Numbers Important?

 

A low glycemic index diet has been associated with improvements in:

Conversely, diets with high glycemic index or glycemic load are strongly associated with type 2 diabetes incidence. Dietary glycemic index is also positively associated with the prevalence of metabolic syndrome, though according to one review, a significant association between dietary glycemic load and metabolic syndrome has not yet been found.

 

Low-Glycemic Index Foods Chart

 

While it’s unlikely you’ll remember the exact GI for every food, it helps to know whether common foods are low or high on the chart.

[Low-glycemic index foods] have a lower glycemic index because they have more fiber, protein and fat compared to carbohydrates.

Below are several foods that have a low average GI, per research published by the ADA’s Diabetes Care and the Journal of Ethnic Foods.

 

Food Average GI
Carrots
(and other non-starchy vegetables)		 39
Strawberry jam/jelly 49
Legumes and beans 16-32
Apples 44
Avocados 40
Bananas 51
Tomatoes 38

 

Other common low-GI foods include unrefined grains, peanuts, squash, cauliflower, nuts and seeds.

 

High-Glycemic Index Foods Chart

 

Common foods that have a high GI (about 76 and higher) are listed below, with their average GI per research in ADA’s Diabetes Care.

 

Food Average GI
White bread 75
Cornflakes
(and other common breakfast cereals)		 81
White rice 73
Potatoes 78
Rice crackers 87

 

Other common high-GI foods include cake, pastries, bagels, processed snacks and maple syrup.

 

How Is Glycemic Index Measured?

 

A food’s glycemic index number is determined through a series of clinical trials with a small number of human test subjects. In these tests, participants’ blood sugar levels are measured before and after eating a serving of food that equals 50 grams of carbohydrates. For example, if potatoes are being tested, each participant would eat however many potatoes are required to meet 50 grams of carbohydrates.

After consuming the food source, blood glucose levels are measured at intervals of usually 15, 30, 45, 60, 90 and 120 minutes.

These varying blood sugar levels are then graphed. At that point, the area under the blood glucose curve (AUC) is calculated, which represents the rise and fall of blood glucose over the two-hour period, The glycemic index is then determined by dividing the AUC of the food being tested by the AUC of the reference food source, then multiplying by 100.

 

Limitations of Glycemic Index

 

Although perhaps a helpful starting point for understanding how certain foods may affect glucose levels, the glycemic index should not be used alone; instead, it should be considered  alongside a food’s energy density and macronutrient profile, recommends the ADA.

The GI isn’t a perfect measurement and it faces a few limitations:

  • Fluctuating numbers. The GI of some foods, including porridge oats, has produced variable results, notes the ADA, suggesting this may be due to differences in cooking methods over the years.
  • Limited effect. Blood sugar is affected by not only a food’s carbohydrate content, but also by the type of carbohydrate (refined or unrefined) and other foods eaten at the same time.
  • Individual variability. GI measurement testing in a handful of individuals does not account for the variability across the population, as there are differences in gut microbiome, genetics, metabolic rate, daily activity, stress and medications, experts note.
  • Inconsistent portion size. A food’s GI is determined based on its serving size that equates to 50 grams of carbohydrates. In reality, most people are likely eating portion sizes that don’t equal the test size, meaning the GI won’t realistically depict the food’s glucose effect.
  • Preparation variability. Even the way a food is prepared alters its GI. For example, a boiled potato has an average GI of 78, instant mashed potato has a GI of 87 and French fries have a GI of 63, per the ADA’s measurements.

Although GI can be a good starting point, Rand and Jones recommend focusing more on eating well-balanced meals to keep your blood sugar in check. Starting a meal with a salad or vegetables or eating fibers, fats and proteins alongside sugars and starches helps slow down digestion and the absorption of carbs, they say.

Eating balanced meals not only helps regulate blood sugar levels, but can also lower your risk for type 2 diabetes or help manage it in the long term, according to Jones. That way, you can focus on enjoying a wide-ranging, healthy meal instead of committing GI numbers to memory.

For those with diabetes, more care and attention should be paid to total grams of carbohydrates at each meal and snacks, as well as regularity in their meal and snack timing, it is recommended to work with a registered dietitian who is a certified diabetes educator (CDE), who can help you create a plan for the timing and amounts of carbs that should be consumed.

 

Glycemic index chart

 

When it comes to how to calculate glycemic index numbers, doctors have measured only certain foods or classes of foods (foods like meats, fats and oil don’t contain carbs).

To determine glycemic index numbers, doctors observe how healthy people’s blood sugar levels change after ingesting carb-containing foods. By measuring subsequent blood sugar levels — and comparing it to a baseline — they can determine where a food falls on a scale of zero to 100, where 100 represents pure glucose and zero is a food with no sugar at all.

Use this glycemic index food chart as a starting point.

Low-glycemic index foods

GI of 55 or less include:

 Medium-glycemic index foods

GI of  56-69 include:

 High-glycemic index foods

GI of  70 or more include:
  • Apple
  • Banana
  • Barley
  • Broccoli
  • Carrots
  • Cashews
  • Chickpeas
  • Dark chocolate
  • Eggplant
  • Lemons
  • Lettuce
  • Limes
  • Mango
  • Oranges
  • Peanuts
  • Pears
  • Peppers
  • Corn Tortilla
  • Pasta
  • Soy Milk
  • Grapes
  • Corn
  • Peas
  • Most Vegetables
  • Kidney Beans
  • Black Beans
  • Plain yogurt
  • Skim milk
  • Strawberries
  • Tomatoes
  • Whole milk
  • Brown rice
  • Couscous
  • Pineapple
  • Popcorn
  • Potato chips
  • Soda
  • Sweet potato
  • Oatmeal
  • Raisins
  • Peach
  • Sucrose
  • Short Bread
  • Pita Bread
  • Wholemeal bread

 
  • Cereal
  • Cheeseburger
  • Corn chips
  • Doughnuts
  • French fries
  • Fried chicken
  • Mashed potatoes
  • Pizza
  • Pretzels
  • Sports drink
  • White bread
  • Bagel
  • Baked Potato
  • Wheat Bread
  • White Rice
  • Rice Milk
  • Watermelon

 

The University of Sydney has a useful Glycemic Index Database you can search.

Another useful FoodStruct Glycemic Index Chart you can search

 

Why calculating the index isn’t exact

 

Determining the glycemic index ratings for individual foods is an imperfect science. Factors like how food is processed or prepared plays a role.

For example, one study of instant oatmeal shows that it had a glycemic index of 79, which is the high range. Yet steel-cut rolled oats have a glycemic index of 55, which puts it in a low glycemic index.

Different versions of the same food will also vary due to ingredients. For example, yogurt that’s marketed for kids is going to taste delicious because it has a lot of sugar or artificial sweeteners, like high fructose corn syrup — versus plain Greek, regular fat yogurt.

They might have very similar amounts of carbs, but the glycemic index is very different because of the number of proteins and fats and the quality and quantity of the sugar that’s in there.

How much you eat of a certain carb-heavy food can also have an effect. For example, a small sip or two of soda won’t have as big an impact on your body as a large portion of whole-grain rice — even though the latter is generally perceived as healthier.

As with many diets moderation is key, as is striking a balance between eating low and high glycemic index foods.

 

 

Food
Group		 Food GI Serving Size GL
(Per Serving)
Vegetables Spinach 0 30g (1 cup) 0.0
Mushrooms 0 70g (1 cup) 0.0
Green Beans 0 135g (1 cup) 0.0
Cauliflower 0 100g (1 cup) 0.0
Celery, raw 0 62g (1 stalk) 0.0
Cabbage, cooked 0 75g (1/2 cup) 0.0
Broccoli, cooked 0 78g (1/2 cup) 0.0
Tomato 38 123g (medium) 1.5
Frozen Peas 48 72g (1/2 cup) 3.4
Yams 51 136g (1 cup) 16.8
Sweet Potatoes 54 133g (1 cup) 12.4
Yellow Corn 55 166g (1 cup) 61.5
Potato 104 213g (medium) 36.4
Potato, baked 111 150g 33.0
Potato, boiled 82 150g 21.0
Parsnips 97 78g (1/2 cup) 11.6
Beets, canned 64 246g (1/2 cup) 9.6
Fruits Sweet Cherries, raw 22 117g (1 cup) 3.7
Plum 24 66g (1 fruit) 1.7
Grapefruit 25 123g (1/2 fruit) 2.8
Peach 28 98g (medium) 2.2
Prunes 29 132g (1 cup) 34.2
Dried Apricots 32 130g (1 cup) 23.0
Pear 33 166g (medium) 6.9
Apple, with skin 39 138g (medium) 6.2
Strawberries 40 152g (1 cup) 3.6
Grapes 43 92g (1 cup) 6.5
Pears, canned 44 248g (1 cup) 12.3
Orange 48 140g (1 fruit) 7.2
Banana 51 118g (medium) 12.2
Mangos 51 165g (1 cup) 12.8
Peaches, canned 52 251g (1 cup) 17.7
Fruit Cocktail 55 214g (1 cup) 19.8
Kiwi, with skin 58 76g (1 fruit) 5.2
Papayas 60 140g (1 cup) 6.6
Raisins 64 43g (small box) 20.5
Apricots, canned 64 253g (1 cup) 24.3
Cantaloupe 65 177g (1 cup) 7.8
Pineapple 66 155g (1 cup) 11.9
Watermelon 72 152g (1 cup) 7.2
Legumes Peanuts 13 146g (1 cup) 1.6
Soy Beans 20 172 (1 cup) 1.4
Kidney Beans 27 256g (1 cup) 7.0
Lentils 29 198g (1 cup) 7.0
Chickpeas, boiled 31 240g (1 cup) 11.3
Pinto Beans 39 171g (1 cup) 11.7
Lima Beans 31 241g (1 cup) 7.4
Baked Beans 48 254g (1 cup) 18.2
Nuts Cashews 22 N/A N/A
Hazelnuts 0 N/A N/A
Almonds 0 N/A N/A
Macadamia Nuts 0 N/A N/A
Pecans 0 N/A N/A
Walnuts 0 N/A N/A
Dairy Ice Cream 38 72g (1/2 cup) 6.0
Low-Fat Ice Cream 47 76g (1/2 cup) 9.4
Whole Milk 40 244g (1 cup) 4.4
Plain Yogurt 36 245g (1 cup) 6.1
Beverages Tomato Juice 38 243g (1 cup) 3.4
Apple Juice 41 248g (1 cup) 11.9
Soy Milk 44 245g (1 cup) 4.0
Grapefruit Juice 48 250g (1 cup) 13.4
Orange Juice 57 249g (1 cup) 14.25
Cola 63 370g (12 oz.) 25.2
Hot Chocolate 51 28g (1 packet) 11.7
Cranberry Juice 68 253g (1 cup) 24.5
Gatorade 78 16g (3/4 scoop) 11.7
Candy/Sweets Peanut M&Ms 33 30g (1 ounce) 5.6
Strawberry Jam 51 2 tablespoons 10.1
Jelly Beans 78 1 ounce 22
Honey 87 2 tablespoons 17.9
Snickers Bar 68 60g (1/2 bar) 23.0
Table Sugar 68 2 tablespoons 7.0
Grains Quinoa 53 150g (1 cup) 13.0
White Rice 89 150g (1 cup) 43.0
Brown Rice 50 150g (1 cup) 16.0
Bulgur 48 150g (1 cup) 12.0
Couscous 65 150g (1 cup) 9.0
Pearled Barley 28 150g (1 cup) 12.0
Cereals Oatmeal 55 250g (1 cup) 13.0
Muesli 66 30g (1 cup) 16.0
Bran Cereal 55 30g (1 cup) 12.0
Puffed Wheat 80 30g (1 cup) 17.0
Cheerios 74 30g (1 cup) 13.3
Rice Krispies 82 33g (1.25 cup) 23.0
Baked Goods Graham Cracker 74 14g (1 squares) 8.1
Kaiser Roll 73 57g (1 roll) 21.2
Bagel 72 89g (1/4 in.) 33.0
Glazed donut 76 75g (large) 24.3
White Bread 70 25g (1 slice) 8.4
Wheat Bread 70 28g (1 slice) 7.7
Banana cake w/sugar 47 60g 14
Banana cake w/o sugar) 55 60g 12
Sponge cake (plain) 46 63g 17
Pita bread, white 68 30g 10
Corn tortilla 52 50g 12
Wheat tortilla 30 50g 8
Hamburger bun 61 30g 9
Miscellaneous Hummus 6 30g 0.0
Popcorn 55 8g (1 cup) 2.8
Cheese Pizza 80 100g 22.0

 

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Most recent revision May 31, 2025 08:32:46 PM