What is glycemic index?
- Alexa Nikolai
- 10 hours ago
- 4 min read
Overview
There are a lot of factors to consider when trying to maintain a healthy diet. While your primary focus should be on eating enough to fuel your body and ensuring you get all the vitamins and minerals you need, you can also begin to consider some of the more nuanced aspects of food. For example, understanding the glycemic index of the carbohydrates you’re eating can help you better maintain balanced blood sugar and keep up your energy all day long.
How does your body use carbohydrates?
Carbohydrates are a type of nutrient that come in three categories: sugars, starches, and fiber. After you consume carbohydrates, your body breaks down sugars and starches into glucose, the simple form of sugar that your body uses for energy. Fiber is beneficial for healthy digestion but is not broken down by the body. The new glucose then passes into your blood stream and is used as the main energy source for your cells. Therefore, you expect to see your blood sugar rise after eating carbohydrates. How quickly it rises depends on the food itself.
Also worth noting, there are two main hormones responsible for keeping your blood sugar in balance over time. Insulin is responsible for moving glucose from the blood into cells and so becomes active when blood sugar levels are high. Glucagon, on the other hand, releases excess glucose stored in the liver into the blood stream when blood sugar levels are low.
What is glycemic index?
As mentioned, not all carbohydrates affect your blood sugar levels in exactly the same way. For this reason, we use the glycemic index (GI) to describe how quickly a certain food can make your blood sugar rise, as compared to pure glucose. Only foods that contain carbohydrates have a GI. The GI scale ranges from 0 to 100, with glucose having a value of 100. Two other common sugars, fructose and sucrose, have GI values of 25 and 65, respectively. Foods that have a low GI value increase your blood sugar slowly, while foods that have a high GI value increase your blood sugar quickly.
What is glycemic load?
Glycemic load (GL) is a measure related to GI that helps to better assess the impact of eating certain carbs. GI values assume you are eating equal amounts of every type of carbohydrate, however, that is often not the case. For this reason, GL accounts for the amount of carbohydrates in a serving. For example, melons such as watermelon and cantaloupe have high GI values, because the carbohydrate in these fruits is easily converted to glucose. However, most of the volume of a melon is water and fiber, so in a single serving, you don’t consume that many carbohydrates. Thus, the GL values of melons are relatively low.
You can calculate the GL of a food by dividing the GI by 100 and multiplying by the grams of carbohydrates in a serving. A GL of 1-10 is considered low, 11-19 is considered medium, and 20 or more is considered high.
What are examples of food with high and low glycemic indices?
Generally, foods are considered to have a low GI if their GI value is 0-55. Foods in this category include pasta, quinoa, bran cereal, oatmeal, carrots, apples, nuts, milk, and yogurt. Foods that have a medium GI of 55-69 include brown rice, honey, and pineapple. High GI foods typically have a GI of 70-100. Examples include white bread, bagels, processed cereals, many snack foods, potatoes, and watermelon.
Sometimes factors other than the food itself can affect the GI value. Typically, processing a food tends to increase its GI value. For example whole fruits have lower GI values than fruit juice, because the processing removes much of the fiber, making the juice easier to digest and convert to glucose. Cooking a food can also affect its GI value; al dente pasta has a lower GI than fully cooked pasta.
Why does glycemic index matter?
For some people, such as people with diabetes, it may be important to pay close attention to the GI of the food you’re eating, since high-GI foods make it more difficult to control blood sugar.
For others, you may not need to know the exact GI values of your food, but having a general sense may allow you to better manage your energy levels throughout the day. High-GI foods make sugar readily available to your cells, creating an initial sugar rush, but once that sugar is gone, you may find your energy levels flagging. Low-GI foods, on the other hand, provide a more steady source of energy that lasts longer.
Furthermore, there is some evidence that diets high in low-GI foods can contribute to weight loss, lower blood pressure, lower cholesterol levels, and lower risk of diabetes. In contrast, diets high in high-GI foods can lead to inflammation, hormonal imbalance, insulin resistance, and pre-diabetes. As always, it is also important to consider other nutritional aspects of the food you’re eating, because GI is just one aspect of a food’s profile. For example, some high-GI foods may provide essential nutrients. Moderation is key.
For women in particular, there may be certain times, such as premenstrually or during perimenopause, when hormonal fluctuations lead to cravings for high-GI foods. Especially after midlife, when your body becomes less efficient at tolerating carbohydrates, managing these cravings can help maintain steady blood sugar levels and prevent dramatic hormonal fluctuations.
Summary
Do you ever feel energized after a snack and then want a nap a short time later? Take a closer look at what you’re snacking on or eating for breakfast and consider switching to an alternative with a lower GI. Low GI foods offer a steadier source of fuel to your body and can help keep you energized all day long.
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