The glycemic index is a tool used to assess a food’s impact on blood sugar levels.

While some foods like eggs and broccoli have a low glycemic index, other foods like cakes and candy have a high glycemic index. Incorporating lower glycemic index foods into your diet may benefit health in several ways, such as supporting healthy blood sugar maintenance and encouraging fat loss.

The glycemic index (GI) is a classification system that ranks carbohydrate-rich foods according to their impact on blood sugar levels. The GI gives an estimation of how quickly a food is digested and absorbed into the bloodstream. 

The GI ranks foods on a scale of 0-100. Low-GI foods score less than 55, moderate GI foods score between 56-69, and high-GI foods score 70 or greater. Glucose, or pure sugar, has a GI of 100 while foods that contain zero carbohydrates, such as steak, have a GI of 0. The higher a food’s GI, the greater its impact on blood sugar.

Though the GI is a useful tool for determining food’s impact on blood sugar and has been connected to some health benefits, it has some major drawbacks. For instance, the GI doesn’t account for important factors such as serving size and what the food is eaten with. While a serving of plain pasta may cause a spike in blood sugar, eating pasta with fibrous vegetables like broccoli and protein such as chicken can have less of an impact.

Also, some healthy, higher-carb foods have similar GIs as ultra-processed foods. For example, a Mars chocolate bar has a lower GI than a piece of watermelon, even though watermelon offers many more nutrients, such as fiber, vitamins, and minerals. For these reasons, the glycemic index is controversial amongst health experts.

Another measure of the glycemic impact of foods is the Glycemic Load (GL), which accounts for both the GI and the ingested serving size of a food, as well as other nutritional content. Though it has some drawbacks, the GL may be a more accurate representation of how food impacts blood sugar.

A low GL is 10 or below, while a high GL is 20 or greater.

In some cases, the GL contradicts the GI, giving some foods that have a high GI a low GL score. For example, though watermelon has a GI score of 74, the GL of a standard serving of watermelon is 4, which is considered low. This can be confusing for people who are using the GI to assess their diet’s impact on blood sugar.

Even though the GI does have significant drawbacks, it has been shown to offer some health benefits.  

The GI ranks foods according to their impact on blood sugar levels. Typically, the higher the GI, the greater the impact a food has on blood sugar. However, it’s important to keep in mind that a food’s impact on blood sugar can depend on several factors, including what the food is being ingested with, the serving size, and how it’s cooked.

Most high-carb foods have a higher GI. This is because carbohydrates have the greatest impact on blood sugar.

Studies show certain groups may benefit from following low-GI diets, including:

• People with type 1 and 2 diabetes: Numerous studies have shown that low-GI diets can help improve glycemic control in people with diabetes. For example, in a review of 10 studies, most of the included studies found low-GI diets resulted in a significant improvement in post-meal blood sugar levels in people with type 2 diabetes. Research also shows that low-glycemic diets can improve blood sugar control in people with type 1 diabetes. 
• People who want to lose weight: Following a low-GI diet may help cut out foods associated with weight gain and excess body fat, such as sweets and sugary beverages. Study results suggest that low-GI diets could be effective for promoting fat loss in certain groups, such as people with metabolic disease. 
• People with fatty liver disease: Non-Alcoholic Fatty Liver Disease (NAFLD) is a liver condition characterized by excess fat buildup in the liver tissue. Following a low-GI diet could benefit people with NAFLD. A review of four studies found that low-GI and low-GL diets reduced liver fat levels and levels of a marker of liver damage called alanine transaminase (ALT) in individuals with NAFLD.

Low-GI diets could benefit overall health as they generally reduce the intake of added sugar, ultra-processed foods, and refined carbs, all of which have a high GI.

However, it’s best to seek individualized dietary advice from a healthcare provider, especially if you have one or more health conditions. 

Foods that have a low GI include meat, poultry, eggs, nuts, beans, and some fruits and vegetables. Low-GI foods contain nutrients that help blunt their impact on blood sugar levels, such as fiber and protein.

Protein-Rich Foods 

Chicken, beef, fish, and eggs all have a GI of zero because they contain zero or very small amounts of carbohydrates and have a minimal effect on blood sugar levels. 

Protein-rich foods slow digestion, which increases feelings of fullness and slows the absorption of sugar into the bloodstream. Pairing higher-carb foods, like grains, with protein-rich foods, like eggs or chicken, can help reduce a meal’s impact on blood sugar. This is why it’s commonly recommended that people with diabetes pair carbs with sources of protein.

Consuming protein-rich foods before a high-carb food can also help reduce post-meal blood sugar spikes. One study found that when people with type 2 diabetes ate skinless grilled chicken breast and a low-carb salad ten minutes before consuming ciabatta bread, their post-meal blood sugar levels were around 40% lower compared to when they consumed ciabatta bread before the chicken and vegetables.

Increasing your overall protein intake and reducing your intake of high-GI carbs may help improve blood sugar control. 

Non-Starchy Vegetables  

Non-starchy vegetables are low in carbs and are usually high in fiber. Like protein, fiber slows digestion and the absorption of sugar into the bloodstream. Studies show that high-fiber diets are beneficial for people with type 2 diabetes, obesity, and many other health conditions associated with high blood sugar levels.

Here’s the GI of common non-starchy vegetables:

• Cabbage: 10
• Mushrooms: 10
• Zucchini: 15
• Onion: 15
• Lettuce: 15
• Broccoli: 32

Adding low-GI non-starchy vegetables to your diet can help increase your fiber intake, which is an easy way to promote healthy blood sugar control and feelings of fullness.

Nuts and Seeds

Nuts and seeds are rich in plant-based protein and fiber, both of which can slow the absorption of sugar into the bloodstream. 

Most nuts and seeds have a low GI, such as:

• Macadamia nuts: 10
• Almonds: 10
• Pecans: 10
• Peanuts: 14
• Hazelnuts: 15

Because they’re rich in fiber and protein and have a low GI, nuts and seeds make a smart choice for people who want to enhance blood sugar control.

Studies show that increasing nut and seed intake may help improve health markers in people with diabetes, such as fasting blood sugar, insulin levels, and the long-term blood sugar control marker hemoglobin (HbA1c).

Eating more nuts and seeds may also help lower post-meal blood sugar in people at risk for developing type 2 diabetes, such as those with prediabetes. A recent study of 66 people with prediabetes found the participants who consumed 20 grams of almonds 30 minutes before each major meal for three months showed significant reductions in post-meal blood sugar, HbA1c, and insulin levels compared to a control group.

The treatment also helped normalize blood sugar levels in a large number of the participants. Among the participants who consumed almonds before their meals, 23% had normal blood sugar levels at the end of the three-month treatment.

Beans and Lentils

Though beans and lentils are high in carbs, they generally have a low GI due to their high concentration of plant-based protein and fiber, which helps offset post-meal blood sugar spikes. 

Here is the GI of popular beans:

• Lentils: 28
• Chickpeas: 28
• Kidney beans: 28

In addition to fiber and protein, beans and lentils are rich in magnesium, a mineral that’s commonly low in many diets. Increasing magnesium intake can be helpful for people with high blood sugar, as magnesium plays an important role in glycemic control. Studies show people with diabetes who have low blood levels of magnesium have poorer glycemic control compared to people who have higher magnesium levels.

Some Fruits

Even though fruits are high in carbs, many fruits have a low GI and can promote healthy blood sugar levels.

Research shows eating fresh fruit can help protect against the development of type 2 diabetes and also improve blood sugar control in people with type 2 diabetes.

A recent review of 19 studies concluded that increasing fruit intake reduced fasting blood glucose concentration in people with type 2 diabetes.

Some examples of low GI fruit include:

• Avocado: 15
• Cherries: 20
• Blackberries: 25
• Pear: 33
• Apricot: 34

Even if you have high blood sugar levels, adding fresh fruit to your diet could benefit your overall health and glycemic control.

Foods with a high GI are usually high in sugar and refined carbs and low in protein and fiber.

Some examples of high-GI foods include:

• White bread
• Refined cereals like cornflakes
• White rice
• Potatoes
• Sugary drinks like soda
• Candies like jelly beans 
• Sweeteners like sugar and honey

Although some foods that have a high GI are low in nutrients, like white bread and candy, other high GI foods, like potatoes and watermelon, are nutritious and offer fiber, vitamins, minerals, and beneficial plant compounds that promote overall health.

Some health experts recommend that people who wish to lower their blood sugar levels and improve their health simply reduce their intake of foods known to significantly impact blood sugar and cause other health issues, regardless of their GI.

For example, rather than following a diet composed of low-GI foods, it may be easier to cut back on sweets, refined carbs, sugary beverages, fried foods, and fast food. You can pair this with increasing your intake of vegetables, fruits, and protein- and fiber-rich foods.

This way, you’re not avoiding nutritious foods that happen to have a high GI, like watermelon and baked potatoes. 

Though following a low-GI diet may benefit the health of some people, it’s generally not necessary for those who are looking to improve their dietary intake, lower blood sugar, and improve other health parameters.

The glycemic index categorizes food based on its impact on blood sugar levels. Foods like meat, poultry, eggs, nuts, beans, and some fruits and vegetables typically have a low glycemic index. These foods are low in carbohydrates or are high in protein and fiber, which can reduce blood sugar spikes.

Foods with a high glycemic index might include foods high in refined sugars and carbs, such as white bread and sugary drinks like soda. However, some foods with a high GI, such as watermelon and potatoes, might offer other beneficial nutrients.

If you’re interested in following a low-GI diet, it’s best to work with a healthcare provider to develop a healthy eating plan that’s specific to your health needs.