The Glycemic Index: What It Is and How to Use It
You probably know someone on a no- or low-carbohydrate diet. Everyone seems to be a little obsessed with carbs these days, and there’s a good reason: the paradigm that we need to eat lots of them to stay energized throughout the day (think of the old food pyramid with grains and starches at the bottom) is shifting toward a more balanced view, and most nutrition scientists now accept that the war on fat was misguided and led Americans to eat more carbs and sugar than ever — leading to higher rates of diabetes and heart disease.
Most of us will continue to eat carbs in some form, however, so it’s important to know how to do that with our body’s best interests in mind. The glycemic index helps us figure out how different foods affect our bodies, specifically blood sugar, so that we can moderate our intake of the carbs that put us in the greatest danger of developing chronic health conditions.
What Is the Glycemic Index?
The glycemic index looks at each carbohydrate’s effect on your body’s blood sugar levels. The higher a food’s score on the glycemic index, the higher and more rapidly it will raise your blood sugar. Foods that have a low to medium glycemic index raise sugar levels more slowly, allowing your body to regulate them and keep them in balance. The three levels of the glycemic index are 1–55, considered low; 56–69, medium; and 70–100, which is high.
Avoiding foods with a high glycemic index helps prevent insulin resistance, which is the first step toward diabetes. Using the glycemic index to guide your dietary choices is especially recommended if you have a history of diabetes in your family.
How Does a High Glycemic Index Food Affect Your Body?
Generally speaking, the higher a food ranks on the glycemic index, the simpler its carbohydrate’s chemical structure. A simpler structure — one or two sugars linked together rather than a more complex chemical group — allows your body to break them down and convert them to sugar more easily, which causes a faster spike in blood sugar levels. Not only that, these simpler carbohydrates usually don’t fill you up as well as more complex ones, leading you to feel hungry again sooner and consume more calories than you actually need.
Insulin, the hormone released by the pancreas to regulate the flow and supply of blood sugar throughout the body, will become ineffective if there are repetitive sugar spikes or a constant higher than normal blood sugar level. A diet that continuously subjects the body to this vicious cycle will put an individual at a higher risk of developing type 2 diabetes, cardiovascular diseases, and certain types of cancer.
How Can a Food’s Glycemic Index Be Affected?
Several factors influence a food’s score on the glycemic index, but basically, the more “broken down” the food is, the higher the glycemic index. Riper fruit will have a higher glycemic index than less ripe fruit, because more of the sugars have been broken down into simpler ones. White bread has a higher glycemic index than whole wheat bread, and whole wheat bread is higher than granola or oatmeal. Juice is higher than a smoothie, which is higher than whole fruits and vegetables. The more processed a food is, the higher its glycemic index.
Benefits of Fiber to a Food’s Glycemic Index
Foods that are high in fiber, the healthier of the three kinds of carbohydrates (the other two are sugar and starch), slow the body’s process of breaking down sugar, which helps to regulate blood sugar levels. So not only does dietary fiber help keep you “regular,” as they say, but it can also help prevent diabetes and other diseases related to high blood sugar.
The Glycemic Index Doesn’t Tell the Whole Story
The glycemic index is just one measure of a food’s overall nutritional value, and it shouldn’t be the end of the conversation about a healthy diet. Bananas have a GI of 62, which is medium ranging to high, but they also contain a lot of fiber and potassium. Watermelon has a GI of 80, which is high, but it contains relatively few carbohydrates at all — so you’d have to eat a ton of it to actually make your blood sugar spike, and watermelon is a great source of other essential vitamins and minerals.
The glycemic index is helpful in certain situations, especially for people at risk of developing type 2 diabetes. Following its guidelines can certainly make for a healthier diet with fewer “bad” carbs in the mix. At the end of the day, though, a healthy diet basically comes down to avoiding processed foods and sugar and eating lots of fruits and vegetables — the “glycemic index diet” is mostly just common sense eating.
