The glycemic index (GI) essentially assigns values ​​to various foods with carbohydrates and rates them according to how great or how small the effects of these foods on your blood sugar level can be. This ranking system shows that not all carbs are created equal when it comes to your blood sugar – some have minimal impact while others can cause huge spikes that can lead to a roller coaster crash later in the day.

But while some experts swear by the glycemic index to help people watch their sugar intake, the ranking system is a little more nuanced than just determining which foods are “good” and which are “bad” for blood sugar. Here’s what you need to know about the buzzword diet.

How does the glycemic index work?

The glycemic index was originally developed for diabetics – both type 1 and type 2. “It created a numeric index or ranking of carbohydrates based on how they affect blood sugar levels when eaten without other foods,” says Robert Glatter, MD, assistant professor of emergency medicine at Northwell Health and attending emergency physician at Lenox Hill Hospital.

“The GI is a measure of how 50 grams of carbohydrates from a particular food affect blood sugar levels. With this measure, the amount of food consumed is the amount that provides 50 grams of carbohydrates, ”says Suzanne Dixon, MPH, RD, epidemiologist and nutritionist. The glucose reaction of a food in question is then compared with a “GI standard”, which is typically a glucose drink, table sugar or white bread, and then given a score. “For example, to determine the GI of carrots, you would have people consume the amount of carrots that 50 grams of carbohydrates provide and compare that to the 50 grams of carbohydrates for a GI standard (sugar or white bread),” she says.

What are some examples of the glycemic index in food?

In general, a food is considered a low GI when it reaches 55 or less. A medium GI food has a score of 56 to 69 and a high GI food has a score of 70 or more.

It can be easy to just assume that all foods with a low score are healthy and those with a high score are not. However, Dixon points out that some healthy carbohydrates might have a similar GI score to less healthy products. Here are some examples:

• White bread: 73
• Sucrose (white table sugar): 65
• Melon: 65
• Treasure: 61
• Sweet corn: 52
• Mango: 51
• Corn tortilla: 46
• Steel cut oatmeal: 42
• Apple juice: 41
• Rye bread: 41
• Chocolate: 40
• Cooked carrots: 39
• Chickpeas: 28
• Soybeans: 16
• Fructose: 15

Remember, melon, a fruit that will keep you hydrated and provide vitamins and fiber, has the same GI as white table sugar. And honey, which is usually billed as a healthier sweetener option than sugar, scores pretty similar in terms of its impact on your blood sugar levels.

How Accurate is the Glycemic Index?

Dixon says the glycemic index can be a helpful tool people should consider when making food choices – especially if they have type 1 diabetes or another condition that requires close monitoring of carbohydrate intake – but it is some caveats. “The GI can be misleading because it doesn’t take serving size into account,” she says. Remember, this is a food rating based on the amount that 50 grams of carbohydrates provide, not necessarily the amount people eat in a typical serving. For example, she says watermelon has a very high GI of 80. However, a two-cup serving size contains 23 grams of carbohydrates, so the 80 actually reflects what would happen to your blood sugar if you were to eat more than four and a half cups – which most people probably don’t.

There’s another measure of how a food can affect your blood sugar that takes serving size into account. “This is known as the glycemic load,” says Dixon. “It more closely reflects how these foods affect our blood sugar and insulin response when eaten in a typical way on a typical diet.” It essentially looks at both how quickly a food affects your blood sugar and how much glucose it actually adds to your bloodstream. Using the watermelon as an example, Dixon says that while the fruit has a high GI, it is also mostly water and doesn’t really contain many carbohydrates per serving. “Given that, the glycemic load is very low at 5,” says Dixon.

There is also strong evidence that not all foods affect humans in the same way, especially when it comes to the GI. A study published in 2016 American Journal of Clinical Nutrition evaluated the blood sugar of 63 healthy people several hours after the administration of 50 grams of glucose either in the form of white bread or in a glucose solution. This test was repeated on the subjects of the study with the aim of assessing the glycemic index of the bread. “But the researchers found some surprising results. There was a 20 percent difference in the measured glycemic index of the exact same food between tests on the same person and there was a 25 percent difference between participants. The bottom line was that the glycemic index was not constant or reliable – even when the food was consumed alone under controlled conditions, ”says Dr. Smoother.

The hard numbers could also lead people to prioritize certain foods over others. “Pure fructose [sugar most often found in fruit] has a GI of 15, “says Dixon as an example.” But while fructose doesn’t have a huge impact on blood sugar levels, it can cause fat to build up in the liver. “Too much fructose from a highly processed food diet (think soda and Baked goods, not whole fruit) is linked to an increased risk of non-alcoholic fatty liver disease (NAFLD), she adds. So fructose doesn’t affect blood sugar as much, but it can be quite harsh on the body, excess liver – another reminder that a healthy diet is really about balance.

How useful are these numbers for a person’s health?

For most people: not much. “It can help in the sense that a diet high in whole foods and minimally processed foods tends to have a lower GI overall,” says Dixon, but it shouldn’t be the ultimate guide on which foods to put on your plate to lay.

Plus, it might be helpful to the diabetic community, but it’s still misleading for them too, says Dixon. “As I said, fructose as a sweetener or form of sugar doesn’t have a big impact on blood sugar levels. But on the other hand, it can promote fat storage in the liver, which is not healthy for anyone, especially people with diabetes, ”she explains. “For this reason, I always encourage anyone with a chronic, diet-related health disorder such as diabetes to see a knowledgeable doctor for nutritional advice.”

“While following the glycemic index or load can help treat diabetics, there is no consistent evidence that following a glycemic index-based diet in nondiabetics can consistently promote or promote weight loss prevent chronic diseases, ”concludes Dr. Smoother. “For those without diabetes, instead of using the glycemic index or stress, it is best to simply reduce added sugar intake by limiting refined or processed foods and sugar-sweetened beverages,” he says. Good to know.

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