Use glycemic index to help control blood sugar


Former Executive Editor, Harvard Health

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Picture an old-fashioned roller coaster with plenty of ups and downs. That’s what your blood sugar and insulin levels look like over the course of a day. The highs that follow meals and snacks drop to lows later on. Learning to eat in a way that makes your blood sugar levels look more like a kiddie coaster with gentle ups and downs than a strap-’em-in, hang-on-tight ride with steep climbs and breathtaking drops can make a difference to your health.

How can you do this? A tool called the glycemic index (GI) can help. It rates carbohydrate-containing foods by how much they boost blood sugar (blood glucose). As someone with diabetes, I use the glycemic index as one strategy to keep my blood sugar under control. And there may be other benefits—low glycemic index diets have been linked to reduced risks for cancer, heart disease, and other conditions.

Comparing carbs

Carbohydrates are the main nutrient in bread, pasta, cereals, beans, vegetables, and dairy foods. All carbs are made up of sugar molecules. Some carbs, like sucrose (table sugar), are just a pair of linked sugar molecules, glucose and fructose. Other carbs, like the starches in potatoes, corn, and wheat, are a tangle of glucose molecules strung together in long chains.

How a carbohydrate-containing food affects blood sugar depends on how quickly the digestive system can break apart the food into its component sugar molecules. It also depends on the sugar molecules present.

The glycemic index measures how much a food boosts blood sugar compared to pure glucose. A food with a glycemic index of 28 boosts blood sugar only 28% as much as pure glucose; one with a glycemic index of 100 acts just like pure glucose. Over the past three decades, researchers have measured the glycemic index of several thousand foods. Click here to see the glycemic index of 100 foods. You can also look up glycemic index values from the University of Sydney’s GI website.

Glycemic index and health

New studies on how the glycemic index of a diet affects health are published almost every week. Some of the latest include:

Using the glycemic index

Using the glycemic index to choose a healthier diet is easier than you might think. “It’s actually quite simple,” says Dr. Jennie Brand-Miller, a professor of human nutrition at the University of Sydney and an advocate of the glycemic index. “Swap high glycemic index foods for low ones.” See the table below for examples of these swaps.

Brand-Miller and others suggest three categories of carbohydrate-containing foods:

Low glycemic index (GI of 55 or less): Most fruits and vegetables, beans (Brand-Miller calls beans “star performers”), minimally processed grains, pasta, low-fat dairy foods, and nuts.

Moderate glycemic index (GI 56 to 69): White and sweet potatoes, corn, white rice, couscous, breakfast cereals such as Cream of Wheat and Mini Wheats.

High glycemic index (GI of 70 or higher): White bread, rice cakes, most crackers, bagels, cakes, doughnuts, croissants, waffles, most packaged breakfast cereals.

Choosing healthy, low-GI foods is easier in Australia, where hundreds of foods carry the GI label.

A few caveats

You can’t rely on the glycemic index alone for choosing a healthy diet. Some foods, like carrot and watermelon, have a high glycemic index, but a serving contains so little carbohydrate that the effect on blood sugar is small. Others, like sugary soda, have a moderate glycemic index because they contain a fair amount of fructose, which has relatively little effect on blood sugar. But they also pack plenty of glucose, which does boost blood sugar, cautions Dr. Frank Hu, professor of nutrition and epidemiology at Harvard School of Public Health.

The glycemic index of a particular food can also be influenced by what it is eaten with. Olive oil or something acidic, like vinegar or lemon juice, can slow the conversion of starch to sugar, and so lower the glycemic index.

The glycemic index isn’t a perfect guide for choosing a healthy diet. But it offers useful information that can help you choose foods that have kinder, gentler effects on blood sugar.

 Swaps for lowering glycemic index

Instead of this high glycemic index food Eat this lower glycemic index food
White rice Brown rice or converted rice
Instant oatmeal Steel-cut oats
Cornflakes Bran flakes
Baked potato Pasta
White bread Whole-grain bread
Corn Peas or leafy greens
Fruit roll-up Whole fruit

Related Information: Eat, Drink, and Be Healthy


  1. concerts

    I’m not sure where you are getting your info, but great topic. I needs to spend some time learning much more or understanding more. Thanks for wonderful info I was looking for this information for my mission.

  2. Manik Dattagupta

    Good research and genuine facts presented with stunning simplicity .

  3. Chicago Family Law

    Definitely great advice to cut back on the carbs, as those are a hidden source of blood sugar spikes. interesting info to keep in mind.

  4. carpet cleaning tampa

    Eating to much sugar for me always makes me crash later on.

  5. Jen McDonough

    Thank you for posting this insightful blog. This will give people information on what food/s to avoid especially those who have diabetes.
    Jen McDonough

  6. Carpet Cleaner Clarence

    The biggest change i ever made was removing sugary drinks from my daily routine. Now its water or 0 sugar flavored water

  7. Nina Reed

    One error. The article says: “Swap low glycemic index foods for high ones.” It should read exactly the opposite – i.e. eat MORE low GI foods, stop eating high GI foods.

    Two tips that work great for me: [1] broad beans – cook with rosemary, after draining add olive oil and parsley. [2] oat biscuits – available in any UK grocery store.

    I used to feel hungry all day long, eating lots of bread [GI index c. 70, even wholemeal], always voraciously hungry. The above two keep me going for a long time, I don’t even THINK of eating! And if I eat them regularly and watch what else I eat, I lose weight. Without a hungry moment.

  8. Frank

    I have read that cinnamon with water and/or food can help reduce blood sugar levels. If so, how often should it be used ?

  9. winifred

    keep d gd work u are doin, by enlightin people on their health.

  10. S.Alhussaini

    Use glycemic index to help control blood sugar

  11. peter franklin robinson

    Sir/Madam, White Long Grain and Basmati Rice G.I.(50-58)are lower than Medium grain white and brown Rice; G.I.(83-87). Ref:New Zealand Healthy Food,July 2005:68-69.

  12. Marg | Spa

    Very easy to follow reading. Kind of makes me feel bad About how I’ve been haphazardly between-eating my body. Will Have The Necessary Adjustment to make for a more healthy food choices.

  13. Bizworldusa

    This information is very useful. So, people should have awareness on this to overcome from blood Sugar. Carbohydrates are main nutrient in bread, pasta, cereals, beans and vegetables. So buy them and eat. It is good diet and controls the problems.

  14. Mark

    Very easy to follow reading. Kind of makes me feel bad about how haphazardly I’ve been tre–eating my body. Will have to make the necessary adjustment for a more healthy food choices.

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