Glycemic Index and Glycemic Load

What’s this thing called the glycemic index? Is it a meal-planning method? Does it work? The glycemic index is a hot topic these days, it seems. But it’s a controversial topic, too. This week, I thought I’d try and shed some light on the glycemic index and hopefully clear up any misconceptions you may have.


The glycemic index (GI) has actually been around for about 20 years. Researchers at the University of Toronto came up with this tool back in the 1980’s. GI is really a ranking system of carbohydrate foods based on how they affect blood glucose levels. Carbohydrate foods are assigned a number between 0 and 100 based on that effect. Foods that have a GI of more than 70 are considered to be “high,” foods with a GI between 55 and 70 are “moderate,” and foods with a GI below 55 are “low.”

Why do foods have different GIs? Much of the reason has to do with how quickly the food breaks down during digestion, and therefore, how quickly blood glucose levels go up after eating. Let’s take a look at some foods and see how they’re classified:

Low-GI Foods
Whole-wheat spaghetti
All Bran
M&Ms peanut candies

Moderate-GI Foods
White rice
Multi-Bran Chex
Life Savers

High-GI Foods
Instant mashed potatoes
Jelly beans

You may be surprised to see that M&Ms have a low GI, while watermelon has a high GI. Does this mean that you should be eating M&Ms and not watermelon? Of course not. This is one of the flaws of the GI. The point is not to completely avoid high-GI foods and only eat low GI foods. Not only is that not practical, but it would mean forgoing many healthy foods that contain important nutrients. Also, many factors can affect the GI of a food, including the following:

  • The variety, the ripeness, and the origin of the food. A boiled potato from India has a higher GI than a boiled potato from Australia!
  • How the food is cooked and for how long. Spaghetti cooked “al dente” has a lower GI than spaghetti cooked until it’s soft.
  • How processed the food is. Old-fashioned, steel-cut oatmeal has a lower GI than instant oatmeal
  • Whether a food is eaten alone or with other foods. A high-GI food eaten with a low-GI food turns the meal into a moderate-GI meal. In addition, adding an acid, such as lemon juice or vinegar, to a food tends to lower the GI of that food.

Other factors can influence how a particular food affects blood glucose levels, too, such as the amount fat and fiber in it (both fat and fiber tend to slow the rise in blood glucose levels after a meal).

One other “downside” of the GI is that fact that the ranking system doesn’t take into account the amount of food one eats. Here’s an example. People are often surprised to see that carrots, much like watermelon, have a high GI. The inclination is to stop eating carrots. But think back to your nutrition class in school—carrots are good for you! Besides being low in calories, high in fiber, and rich in beta-carotene, a half-cup of carrots has just 8 grams of carbohydrate. So why does it have a high GI?

The GI was originally developed by researchers for research purposes, and it was calculated from servings of food that contained 50 grams of carbohydrate. In the case of carrots, you’d have to eat about 1 1/2 pounds to get that much carbohydrate! Would you eat that many carrots at one time? Probably not. The GI doesn’t take into account realistic serving sizes. However, the glycemic load does.

Glycemic load (GL) is the amount of carbohydrate in a food multiplied by that food’s GI. The GL is also a ranking of how foods affect blood glucose levels, but unlike GI, the GL takes serving size into account. Like GI, the lower the GL, the lower the spike in blood glucose levels. Low-GL foods have a value of 10 or less; moderate-GL foods have a value of 11-19; and high-GL foods have a value of 20 or more.

Back to the carrots, then. Carrots have a GI of 71. If we multiply the 8 grams of carb in a half cup by .71, we get a GL value of roughly 6. Therefore, carrots are a low-GL food. This means that, unless you truly are going to eat a pound and a half at a time, carrots don’t have a big impact on blood glucose levels.

The concepts of glycemic index and glycemic load can be overwhelming for some people, and may not be practical for everyone. Keep in mind that these are adjunct, or supplemental, meal planning tools to use if you’re already carb counting or following another meal planning method. You need to master the basics, first!

Is there a way to easily integrate the GI/GL into your day-to-day meal planning? Yes. Here are some suggestions to get you started:

  • Choose fresh fruits and vegetables over canned versions or juices.
  • Eat more beans and peas, such as chickpeas, kidney beans, and lentils.
  • Limit refined grains, such as white bread, white rice, and processed, low fiber cereals.
  • Choose whole grain breads, cereals, pasta, and rice whenever possible.
  • Make your own salad dressings using vinegar or lemon juice.

For more information on glycemic index and glycemic load, check out the following Web sites:

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  • William Stockwell

    We have been looking for The Glycemic index for Raspberries,Blue Berries and Black Berries. Can you help us, or suggest a web site. Thank you, Bill Stockwell

  • ann

    I found blueberries to be 53.

  • denniskm

    I have noticed that when I eat the lower glycemic indexed foods I still have to take as much insulin as the higher ones. For instance whole wheat pasta compared to white pasta and whole wheat bread compared to white bread. Thanks

  • acampbell

    Thanks for the info, Ann. And to further answer your question, Bill – most berries have a GI of less than 50, so they’d be considered low glycemic index choices.

  • acampbell

    Hi Dennis,

    Most insulin users still need to take the same amount of insulin for a lower GI food. The carbohydrate amount usually isn’t much lower in a low GI food compared to a high GI food. What varies is the length of digestion – in other words, it takes longer for a lower GI food to be digested and absorbed, which means that it affects blood glucose levels more slowly. Some people need to delay their insulin injection when eating lower GI foods.

  • Dan2

    All I want to know is: Is it bad that I’m eating one regular box of white noodles(spaghetti or angel hair) per day??? That’s what i’ve been doing.

  • acampbell

    Hi Dan2,
    That’s a little tricky to answer without knowing details. For example, how are your blood glucose and triglyceride levels doing? How is your weight? Are you eating the pasta all at one meal, or spacing it out? Are you getting an adequate amount of protein, fruits, vegetables and whole grains?

  • florence

    When I got up this morning, my blood sugar was 135. I had a sustutue egg with a slice of swiss cheese on 2 slices of wheat bread. Then I had a half cup of strawberries and grapes. A couple of hours later, my blood sugar was 165. What did I eat that I should not have, I thought that meal was good for me.

  • acampbell

    Hi Florence,
    It’s to be expected that your blood glucose will rise after eating a meal that contains carbohydrate (bread, strawberries, grapes). A blood glucose of 165 is not that high two hours after a meal. However, ideally, your glucose should be down around 90 to 130 before lunch. If it’s not, you may either need to reduce your carbohydrate intake slightly or, if you’re on medication, talk to your provider about increasing the dose. Don’t forget that doing some physical activity will help lower glucose levels, too.

  • dorcas gibbs

    I found the comments truly helpful. Some info I knew and some I didn’t. Very interesting and helpful. It is so hard to put the right combo food choices together and not get bored. We need to read all info we can get our hands on. Thanks to all who contributed.

  • Nathan

    Thank you for responding Amy! When I learned that the amount of carrots I was regularly had a GL of >23, I was a bit worried. But I feel better now. Carrots satisfy so many cravings: sweet and crunchy like cookies and they contain lots of water so I’d hate to give them up. I do exercise regularly as well – anywhere from 600-2k calories of cardiovascular at the gym (well if the numbers on the machines are to be believed and they’re at least useful as a relative measure of performance) plus a 40 minute round trip bicycle commute. Loaded with all that quick burning energy certainly makes me feel stronger during evening commute/workout.

  • Nathan

    That’s sort of scary. I eat a pound of carrots a day – I get one of those bags of peeled baby carrots and munch on them at work. 5 days a week. From the info above, a pound of carrots would have a GL of ~24, well into the high GL range, in addition to everything else I eat. Does eating that much set me up for Type II diabetes? I mean how ridiculous would that be – to acquire diabetes from over consumption of carrots!

  • acampbell

    Hi Nathan,
    Yes, it would seem ridiculous to get diabetes from eating too many carrots! But that’s probably unlikely to happen, especially since it sounds like you’re spreading out your carrot intake over the course of at least several hours, and not eating the whole pound at one sitting. And the other benefit to eating these carrots is that you’re filling up on something nutritious, rather than hitting the vending machine, for example. There are many factors that determine how and why someone gets type 2 diabetes, including the other types of food that you eat, your activity level, your weight, your family history and ethnicity. As the saying goes, everything in moderation. If your overall diet is on the healthy side, you’re fitting in activity most days of the week, and you’re at a healthy weight for you, it sounds like the carrots can continue to be part of your daily schedule.

  • Gage’s mom


  • acampbell

    Hi Gage’s mom,

    I haven’t come across too much on the Internet as far as meal planning and glycemic index. However, you might try two books: The New Glucose Revolution and The New Glucose Revolution Pocket Guide to Healthy Kids. These are part of a series of books by Jennie Brand Miller, a dietitian and researcher based in Australia, that address the glycemic index. Your local bookstore should carry them so look through them and see if they might be helpful to you.

  • Mary

    I’m looking for the lists DSM published a while back listing portion sizes of many foods and the caloric value. Could you please e-mail it to me or let me know where to find it? And how about a glycemic index to go with it? I have a senior diabetic client who insists she knows all there is to know about these subjects but her A1c was 9.4 when tested last month. She has been under stress (her husband passed away after a lengthy illness) but she eats lots of white bread, nuts, TV dinners and other stuff like ice cream and pies. I have been an insulin dependent diabetic for over 10 years with an A1c testing out at 6.4 last Dec.and just want to pass on some documented info on these subjects. I don’t want to preach to her or alienate her. Thanks, Mary

  • Darius
  • Renita

    I really enjoyed the article as it clearly answered my questions about GI/GL. My 45 year old son just had a heart attack and had recently been diagnosed with type II diabetes. He understands the obvious foods he needs to stay away from, but his work schedule prevents him from sitting down to a family meal in the evenings. He needs help with learning to eat the proper foods and how to combine them. Any cookbook suggestions that could help with snacks he can take to work at night. He is concerned about, heart healthy, diabetes healthy foods and counting carbs. He will have to do his own cooking, so this is a challenge, as he doesn’t know how to cook except for the occasional grilling.

  • acampbell

    Hi Renita,

    There are a lot of good cookbooks out there, and choosing a cookbook is often a matter of personal preference. That being said, I’d suggest you and he visit the American Diabetes Association’s Web site, as they have a number of cookbooks that might be appealing.

    Also, don’t forget to check out the cookbooks on this Web site.

  • brenda

    would someone give me the glycemic load not the glycemic index of 1/2 cup of blueberries?

  • acampbell

    Hi brenda,

    One half-cup of fresh blueberries has a glycemic load of approximately 3. Foods with a glycemic load of less than 10 are considered to have a “low” glycemic load.