The glycemic index (GI) reveals how a food affects your blood sugar.
When you consume carbohydrates, the body converts them into glucose (sugar.) The pancreas releases insulin in order to move the sugar from the bloodstream into the cells where it can be used for energy.
If there is not a sufficient amount of insulin available, or if the body’s cells are resistant to insulin, the excess sugar remains in the bloodstream resulting in high blood sugar.
A food’s Glycemic Index is determined by referencing the carbohydrates in each food against glucose (sugar.) Glucose has a Glycemic Index of 100.
If the food item affects blood sugar less than the glucose does, it is given a lower GI. A food can be classified as either low, medium, or high on the Glycemic Index. Higher GI foods raise blood sugar more than foods with a low or medium GI.
Low GI Foods (Glycemic Index of 55 or less)
- Oatmeal (rolled or steel-cut), muesli, oat bran
- Brown rice, quinoa, barley, bulgur wheat
- Dried beans, legumes, lentils
- Starchy vegetables like sweet potato, yams, carrots
- Non-starchy vegetables and most fruits
- Most dairy (milk, cheese, yogurt)
(Meats, seafood, and fats like butter and oil are not included in the GI because they do not contain carbohydrates.)
Medium GI (Glycemic Index of 56-69)
- Whole wheat bread
- Potato chips
- Microwave popcorn
- Grapes and raisins
High GI (Glycemic Index of 70 or higher)
- White bread, bagel, pizza crust
- Short-grain white rice
- Russet potato
- Pretzels, rice cakes, saltine crackers
- Pineapple and melon
Research has shown that both the amount and the type of carbohydrates in a food determine its effect on blood sugar.
When the body consumes a simple carbohydrate, it responds the same way as if it had consumed sugar. There is no additional nutrition available to slow the absorption of the resulting sugars into the bloodstream and therefore, blood sugar rises.
Complex carbohydrates, however, are converted into sugar more slowly, giving the body a better chance to regulate the amount of sugar in the blood.
The GI of a food can be lowered when eaten in combination with other foods. When eating a high GI food, you can combine it with low GI foods for balance. The best way to enjoy carbs is in combination with foods that will help to slow their absorption even more.
If the complex carbohydrate is paired with fiber, protein, or fat, it is absorbed even more slowly and blood sugar will remain more stable. For example, instead of a plain piece of toast for breakfast, try a slice of toasted whole wheat bread topped with a slice of gruyere cheese, an egg and a few slices of avocado.
Consider the form of the food and how it has been processed. Generally speaking, the more cooked or processed something is, the higher it’s GI will be. For example, fruit juice has a higher GI than whole fruit, mashed potatoes have a higher GI than a whole baked potato, and packaged instant oatmeal has a higher GI than steel-cut oats.
Do not forget to take nutritional value into account along with GI. Many nutritious foods will have a GI higher than foods with no nutritional value whatsoever. For example, parsnips have a higher GI than a peanut and chocolate candy bar. Even though the vegetable’s GI is higher, it is still the more healthful choice overall.
In turn, just because a food is low glycemic doesn’t mean you can eat as much of it as you like. The GI represents the effect of the carbohydrate itself, and does not take into account that portion in which it is consumed. For example, even though whole wheat bread is a better choice than white bread from a GI standpoint, if you eat four sandwiches, your blood sugar will spike (and you’ll likely be sick!)
While only a piece of the puzzle in managing diabetes, the Glycemic Index may prove helpful for individuals who want to put some extra effort and thought into how their food choices can affect their blood sugars.