Glycemic Index of Bananas: Impact on Your Blood Sugar Levels

Bananas are a delicious and convenient fruit to bring on the go. But what does the glycemic index of bananas say about its impact on our overall health?

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by
Chelsea Rae Bourgeois, MS, RD
— Signos
Health writer
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Updated by

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Science-based and reviewed

Published:
July 18, 2024
March 6, 2023
— Updated:

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Bananas are a nutritious and delicious fruit, rich in vitamin C, potassium, vitamin B6, manganese, magnesium, and fiber. Still, while this healthy fruit offers many potential health benefits, it can cause blood sugar spikes if eaten in excess.

Maximizing their benefits often means eating bananas in moderation. In this article, we’ll explain the science behind bananas and their glycemic index. And we’ll discuss ways to incorporate them into a healthy diet, not just for diabetes management but for overall health.

First Things First: What Is the Glycemic Index?

The glycemic index (GI) assigns a number to a food based on how quickly it can raise your blood glucose levels. These carbohydrate-containing foods are ranked on a scale of 0 to 100 and divided into low, medium, and high-glycemic categories:

  • High-glycemic index foods = GI score of 70–100
  • Medium-glycemic index foods = GI score of 50–69
  • Low-glycemic index foods = GI score of 20-49

While a food’s glycemic index is primarily predetermined by its carbohydrate content, it can also be affected by processing and cooking methods. For example, minimally processed whole grains typically have lower GI values than refined grains. If a carbohydrate requires cooking, the temperature, duration of cooking, and cooling and reheating can all affect its GI score.

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Glycemic Index of Bananas

Do bananas raise blood sugar? You bet! But that’s why we eat them. They are a carbohydrate source, meaning they provide us with energy as our bodies digest them. The trick is to understand how our bodies respond to their glycemic index.  

So, how fast will a banana raise blood sugar? Bananas have an average glycemic index of 50, making them a medium-glycemic index food.1 However, a banana’s GI score can vary depending on multiple factors.

For example, its ripeness will determine how much sugar is in a banana and its GI score. Generally, the more ripe a banana is, the higher its GI value will be. Also, portion size determines how many grams of carbohydrates you consume or the food’s glycemic load. The larger your portion size, the more grams of carbs you’ll eat.

Why Does Glycemic Index Vary With Ripeness?

Amazingly, a banana’s glucose levels will increase as the fruit ripens, changing its GI score throughout the process. At the start, green, unripe bananas contain resistant starch and less sugar than ripe bananas. Resistant starches are long chains of glucose that act similarly to fiber. This type of carbohydrate is resistant to digestion in the small intestine, meaning less glucose will be released into the bloodstream.

For this reason, unripe bananas are less likely to cause a rise in your blood sugar levels.2 In addition, resistant starches may also feed the friendly bacteria in your gut, which has been linked to improved blood sugar management.3

As bananas ripen, they turn yellow. This indicates that they have less resistant starch and more sugar, which will cause your blood glucose levels to rise faster. Therefore, their glycemic index increases as bananas ripen, giving them a higher GI value than unripe bananas.

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Green

If you want a banana in its lowest GI form, go for an unripe, green banana. Green bananas typically have a GI score lower than the average 50.

Yellow

As a banana turns yellow, its glucose content increases. With more glucose, it’s more likely to cause an increase in your blood sugar, thus giving it a higher GI score than the average 50.

Spotted (Ripe)

Last but not least, fully ripened bananas have the highest GI score of all the stages. You often see recipes like banana bread that call for spotted bananas. This is because they have more glucose and a much sweeter taste. Fully ripe bananas can have a high GI, even up to a score of 75.

Are Bananas Considered Healthy? 

Bananas can be a nutritious part of a well-balanced diet. However, be aware of the banana’s ripeness and portion sizes to avoid spiking your blood sugar levels. 

The carbs in a banana can also provide energy, but too much at once can send your sugar levels over the edge. Since unripe bananas are considered a low-GI food, they can be a great way to incorporate more nutrients into your meals without significantly affecting blood glucose.

To enjoy bananas with your overall health in mind, monitor your portion sizes and remember that other parts of your meal may also affect your blood glucose.

You can also incorporate different types of bananas to adjust your carbohydrate intake, but consider these tips:

Choose Yellow and Firm Bananas

Look for bananas that are yellow and have a firm feel. The banana will be firm if the fruit’s resistant starches are intact. As the resistant starches break down and glucose content increases, the banana will get softer and mushier.

Choose Smaller Bananas

Choosing a small banana can help reduce the number of carbs you consume. However, if you can’t find a small or medium-sized banana, break a large banana in half and share the other half with a friend.

Eat Them in Moderation

Moderation is the name of the game when it comes to well-balanced nutrition. The same goes for your banana intake. Eating bananas in moderation, whether through portion sizes or frequency, can help you capitalize on their health benefits while maintaining balanced blood sugars.

Combine With Other Foods

Eating bananas with other foods gives your body other macronutrients to digest, helping to avoid blood sugar spikes that might occur if eating bananas alone. Foods like nuts, oats, and yogurt are rich in protein and healthy fats and pair well with bananas.

Bananas vs. Apples

All foods can fit into a well-balanced diet, including apples and bananas. In fact, including various fruits can help you meet your nutrition needs on both the macro and micronutrient levels because each food has its unique nutrition profile.

Apples and bananas provide very similar nutrition.One medium apple contains around 104 calories and 27 grams of carbs, whereas one medium banana contains 29 grams of carbs and about 112 calories.4,5 They also contain 3-4 grams of dietary fiber and a decent amount of vitamin C. However, apples have a notable amount of antioxidants, and bananas are rich in potassium.

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3 Healthy Banana Recipe Ideas to Try 

Bananas can add a boost of nutrients and flavor to a variety of recipes. Try some of these delicious recipes next time you want to incorporate bananas into your meals.

Banana Bread Casserole

For this recipe, you’ll need ripe bananas, thick slices of bread, eggs, water, and milk. Mix torn bread with slices of bananas in an oven-safe baking dish. Then, in a separate mixing bowl, beat your eggs, milk, and water. Add brown sugar to taste if desired.

Pour the mixture over the bread in your baking dish, and bake at 350 degrees until golden brown. You can serve it with vanilla yogurt on top or eat it on its own.

Banana Pancakes

Spice up your favorite pancake recipe by adding bananas to the mix. You can mash the bananas and stir them directly into the pancake mix or slice them up and add them to the pancakes as you pour the mixture into the skillet. The bananas will add delicious flavor and nutrients to your breakfast menu!

Green Banana Smoothie

Bananas can make a great addition to your favorite protein smoothie recipes. Consider looking for protein powders low in carbs, so you can add bananas for taste and texture without overdoing it on the carbs. By adding bananas, your carb intake comes from natural sugars versus added sugars from a high-carbohydrate protein powder.

I like to use a vanilla protein powder blended in almond milk with one-half banana, a large handful of spinach (or another leafy green veggie), and a tablespoon of peanut butter. The smoothie has a delicious flavor and a beautiful green hue. Because bananas contain fiber, they can increase your satiety, making that protein smoothie even more nutritious.

Learn How to Improve Your Nutrition and Monitor Your Glucose Levels with Signos’ Expert Advice

Signos’ continuous glucose monitoring can improve your health by helping you keep track of your diet and its effects on your blood sugar levels. Understanding our blood sugar response to food isn’t just for those with type 2 diabetes. Our blood sugar levels affect heart disease, weight loss, kidney function, and skin health.

Signos gives us real-time data, showing how our bodies respond to the food we eat. By knowing how our body is affected by the carbohydrate content of our diets, we can develop well-balanced eating habits that serve our overall health well.

Find out if Signos is a good fit by taking a quick quiz! And if you have questions about your individualized nutrition needs, consider meeting with a registered dietitian!

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References

  1. Home. – Glycemic Index. (n.d.). Retrieved February 19, 2023, from https://glycemicindex.com/gi-search/?food_name=banana&product_category=fruit&country=&gi=&gi_filter=&serving_size_%28g%29=&serving_size_%28g%29_filter=&carbs_per_serve_%28g%29=&carbs_per_serve_%28g%29_filter=&gl=&gl_filter=
  2. Falcomer, A. L., Resende Riquette, R. F., Ginani, V. C., & Zandonadi, R. P. (2019). Health Benefits of Green Banana Consumption: A Systematic Review. Nutrients, 11(6). https://doi.org/10.3390/nu11061222
  3. Bird AR, Brown IL, Topping DL. Starches, resistant starches, the gut microflora, and human health. Curr Issues Intest Microbiol. 2000;1(1):25-37.
  4. Fooddata Central Search Results. FoodData Central. https://fdc.nal.usda.gov/fdc-app.html#/food-details/1102644/nutrients. Accessed February 20, 2023.
  5. Fooddata Central Search Results. FoodData Central. https://fdc.nal.usda.gov/fdc-app.html#/food-details/1102653/nutrients. Accessed February 20, 2023.

About the author

Chelsea Rae Bourgeois is a registered dietitian nutritionist with several years of experience working in the clinical setting. Once a track and field athlete on a competitive stage, she now finds joy in combining her passions as a health writer to help people embrace their wellness through nutrition and fitness.

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