How Bananas Affect Diabetes and Blood Sugar Levels

Diabetes mellitus, or diabetes, is a disease affecting the regulation of blood glucose (sugar) levels.

An organ called the pancreas creates the hormone insulin, which helps keep blood sugar levels in a healthy range.

With diabetes, the pancreas either doesn’t make enough insulin, or the body doesn’t respond to it well. Without proper insulin function, blood sugar levels rise and can lead to health problems if left untreated.

Diabetes is becoming more prevalent worldwide. As of 2015, 30.3 million people in the United States, or about 9.4 percent of the population, had diabetes. Unfortunately, more than 1 in 4 people with diabetes don’t know they have it. Having undiagnosed diabetes increases the risk of complications from lack of prompt treatment.

Many people also have prediabetes, a condition where blood sugars are slightly elevated but not high enough to be considered diabetes. Having prediabetes is a significant risk factor for eventually developing type 2 diabetes. The U.S. Centers for Disease Control (CDC) estimates that up to 30% of people with prediabetes will develop type 2 diabetes within five years of their prediabetes diagnosis.

One of the ways to help promote healthy blood sugar levels is through healthy lifestyle habits. Focusing on eating nutritious foods that are good for blood sugar is one of the most important aspects of treating both diabetes and prediabetes. Incorporating blood sugar-friendly foods into meals and snacks is good for overall health, can help promote good energy levels and increase the feeling of satiety, which can help reduce hunger and cravings.

Fruit is often vilified for its sugar content, making people with diabetes wary of including fruit in their diet. This is an unfortunate misconception since many fruits are incredibly nutrient-rich and a healthy part of a balanced diet.

A diet including fruit, has been shown to have many potential health benefits, including a reduced risk of type 2 diabetes, along with a reduction of many other chronic diseases. One study even sought out to see if restricting fruit in people with existing diabetes would improve blood sugar or any other health outcomes, which it did not.

Fruit and other plant-based foods are the backbone of a Mediterranean diet, which is associated with a reduced risk of developing type 2 diabetes. Some studies have found an 83% reduction in diabetes risk when a Mediterranean diet was followed. 

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Are bananas good for diabetics?

Bananas are a fruit mainly composed of water and carbohydrates. Carbohydrates are a macronutrient that has the biggest impact on blood glucose levels.

There are three components to the carbohydrate group: sugars (such as in fruit), starch (such as “starchy” vegetables like potatoes, beans/legumes, and grains), and fiber, which is found in plant-based foods. Of all of these, fiber is the only carbohydrate not to raise blood sugar because the body can’t absorb it. As a result, high-fiber foods tend to raise blood sugar less than low-fiber foods.

Carbohydrates are broken down into glucose molecules, or blood sugar, during digestion. Blood sugar levels rise after consuming carbohydrates, which is why people with (and at risk for developing) diabetes are encouraged to eat various foods and be mindful of their carbohydrate portions, as eating a carbohydrate-heavy diet can lead to elevated blood sugars.

Carbohydrates have the biggest impact on blood sugar levels compared to protein and fat, the other two macronutrients. This is why there is such a focus on carbohydrates when it comes to managing blood sugar levels and why fruit is one of the foods people with diabetes may be cautioned about eating.

Many questions arise when considering the relationship between bananas and diabetes. Bananas, among many other types of fruit, are a good option for people with diabetes. Fruit isn’t “bad” for people with diabetes just because it raises blood sugar. Like any food that raises blood sugar, the more important thing is to be mindful of portion size and focusing on an overall balanced diet to promote healthy blood sugar levels for those with diabetes. 

Eating too much of any food, even healthy food like fruit, can become detrimental to health and diabetes management. Focusing on balanced meals and snacks is more important than singling out a single food. For instance, eating a banana with a handful of nuts is less likely to cause a blood sugar spike than having banana slices on top of sweetened cereal with cow’s milk.

Fruit contains natural sugar, fiber, and nutrients, making it a nutritious choice. On the other hand, added sugars found in many foods such as yogurts, cereals, and even pasta sauces are the kind to avoid since diets rich in added sugars are associated with increased risk of several chronic diseases, including heart disease and cancer.

Glycemic index

One of the factors determining how much food impacts blood sugar level is the glycemic index. Glycemic index (GI) is a value used to measure how much a food raises blood sugar and is based on a number from 0-100. Foods are usually described as low (GI of 55 or less), medium (56-69), or high (GI of 70+) glycemic index based on the number.

The lower the glycemic index, the less that food will raise blood sugar levels. The average banana has a low glycemic index of 51, while slightly under-ripe bananas have a glycemic index of 42.

One of the drawbacks of the glycemic index is that it only provides insight as to how one single food impacts blood sugar levels. People usually eat a diet of mixed foods, which negates the accuracy of the glycemic index. 

Resistant starch

An unripe banana is higher in starch than sugar. As the green banana ripens and turns yellow, that starch turns to sugar, making it sweet. Bananas are especially rich in resistant starch, a type of carbohydrate that resists digestion and is thus fermented by the gut’s natural bacteria in the colon.

When resistant starch is fermented, it creates short-chain fatty acids, which can promote gastrointestinal health. Resistant starch may have other health benefits, such as reducing colon cancer risk, heart disease and improving insulin sensitivity.

The longer the banana sits and ripens, the lower the resistant starch quantity, so it’s best to eat bananas while still slightly green to maximize the resistant starch content’s benefits.


Fiber is a carbohydrate but doesn’t affect blood sugar levels because it isn’t absorbed by the body, similar to resistant starch.

Fiber can also slow gastric emptying, meaning the food takes longer to be broken down into sugar, which is one way it can help diabetes. Eating fiber-rich foods can help avoid blood sugar spikes, which can occur when eating rapidly-digested carbohydrates, such as white bread and refined sugar. 

Bananas are rich in fiber, with one medium banana containing around 2.5 grams of dietary fiber. For perspective, it’s recommended to consume around 25-35 grams of fiber per day; however, most people fall short of this recommendation.

Fiber is beneficial for weight management, as it promotes a feeling of satiety. Fiber, particularly soluble fiber, can reduce LDL cholesterol levels, also known as “bad” cholesterol. High LDL levels are a risk factor for forming blockages in the arteries and can also increase inflammation. Fiber intake has been associated with improvements in blood sugar and hemoglobin A1c levels and helps prevent diabetes. 

When counting carbohydrates for blood sugar control, one of the important things to note is the net carbohydrate content. The net carbohydrate amount is the total carbohydrates minus dietary fiber. The resulting “net carbs” is the amount that should be counted because it affects blood sugar.

Fiber is subtracted from total carbohydrates because it doesn’t raise blood sugar since it can’t be digested. Therefore, choosing higher-fiber foods will lower net carbohydrate totals, which is one strategy for promoting optimal blood sugar levels.

Banana nutritional profile

The nutritional breakdown of a medium banana is as follows:

  • Calories: 105

  • Protein: 1.3 grams

  • Carbs: 22.8 grams

  • Fiber: 3.1 grams

  • Fat: 0.4 grams

Bananas are a good source of dietary potassium. Potassium is a mineral important for the regulation of blood pressure. This is especially important for people with diabetes as they are at increased risk of heart disease, which often includes high blood pressure. Eating fiber- and potassium-rich foods are some ways to help promote heart health through the diet.

Potassium is also important for muscle health and may prevent exercise-induced muscle cramps and soreness, which is one of the reasons it’s a popular snack offered at sporting events such as marathons.

How much sugar is in a banana?

According to the United States Department of Agriculture (USDA), one medium banana weighing 118 grams contains 14 grams of sugar. Bananas are higher in sugar compared to other fruits such as berries and apples but are lower than some, such as mangoes and grapes.

Natural bananas (and fresh fruit in general) are healthier than fruit juices and dried fruit, which tend to raise blood sugar more than fresh or frozen fruit. Fruit juices don’t contain any fiber, which means it can break down into sugars much faster than fruit flesh containing fiber. Dried fruit concentrates the fruit, so it’s easier to eat more than you would normally if it was fresh. 

Many dried fruits also contain added sugar, which further promotes higher blood sugar levels. Banana chips are the dried version of bananas and often are coated in sugar or honey to enhance their sweet flavor. They may also be fried in oil to enhance flavor, making them a higher-calorie food than a plain banana.

Diet tips

For those with diabetes or who are trying to watch their blood sugars, it is possible to include fruits such as bananas in their diet while still achieving blood sugar goals. Some tips to avoid high blood sugar while also enjoying fruit:

  • Include a protein source with fruit. Protein takes longer to digest than the carbohydrates in fruit, so it can help slow the rise in blood sugar when fruit is eaten. Adding peanut butter to a banana or blending a banana in a smoothie with plain Greek yogurt are examples of balancing carbohydrates with protein.

  • Try to spread carbohydrate intake out consistently throughout the day. Eating a carbohydrate-heavy meal or snack is more likely to spike blood sugar levels compared to spreading carbohydrate consumption out evenly. For instance, if you’re eating oatmeal with a glass of milk for breakfast, it would be better to save the banana for a snack since the breakfast is already high in carbohydrates from the oatmeal and the milk.

  • Stick with fresh or frozen fruit. Canned fruit can have added sugar in the form of syrup and is usually lower in fiber. Dried fruit can have sugar added to it, and it’s easier to eat more fruit in dried form than fresh because the volume is lower while maintaining the carbohydrate content. On the other hand, plain frozen fruit is just as nutritious as fresh and can help reduce food waste, and doesn’t have added sugar.


Bananas are a type of fruit, which is a type of carbohydrate. Carbohydrates turn into blood sugar when digested, which is why they are often focused on when considering a healthy diet for diabetes.

Bananas have many health benefits from their resistant starch and fiber content, which may promote stable blood sugars as well as reduce the risk of other diseases such as heart disease. They do contain natural sugar but are preferred over foods with added sugar, such as sweetened cereals and other processed foods.

To help reduce the impact bananas have on your blood glucose level, try combining them with a protein source, as well as spreading out carbohydrate intake consistently throughout the day. When bananas are part of an overall balanced diet, they can be a very healthy part of a management plan for diabetes.

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  2. Rationale for the Use of a Mediterranean Diet in Diabetes Management Gretchen BensonRaquel Franzini PereiraJackie L. Boucher
  3. Christensen AS, Viggers L, Hasselström K, Gregersen S. Effect of fruit restriction on glycemic control in patients with type 2 diabetes–a randomized trial. Nutr J. 2013;12:29. Published 2013 Mar 5. doi:10.1186/1475-2891-12-29
  4. Rippe JM, Angelopoulos TJ. Relationship between Added Sugars Consumption and Chronic Disease Risk Factors: Current Understanding. Nutrients. 2016;8(11):697. Published 2016 Nov 4. doi:10.3390/nu8110697
  6. McRae MP. Dietary Fiber Intake and Type 2 Diabetes Mellitus: An Umbrella Review of Meta-analyses. J Chiropr Med. 2018;17(1):44-53. doi:10.1016/j.jcm.2017.11.002

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