How Bananas Affect Diabetes and Blood Sugar Levels

If you have diabetes, being aware of the amount and type of carbs in your diet is important.

This is because carbs raise your blood sugar level more than other nutrients, which means they can greatly affect your blood sugar management.

When blood sugar levels rise in people without diabetes, their bodies produce insulin. This helps move sugar out of the blood and into cells, where it’s used or stored.

However, this process doesn’t work as it should in people with diabetes. Instead, either the body doesn’t produce enough insulin or the cells are resistant to the insulin that is made.

Without proper diabetes management, you may experience blood sugar spikes after eating high carb foods or have constantly high blood sugar levels, both of which are unhealthy.

How much sugar is in a banana?

One medium banana (about 126 grams) contains 29 grams of carbs and 112 calories. The carbs are in the form of sugar, starch, and fiber (3).

A medium banana contains about 15 grams of sugar (3).

Summary

Bananas do contain simple carbs, which can cause blood sugar levels to rise more than other nutrients.

In addition to starch and sugar, a medium banana contains 3 grams of fiber (3).

Everyone, including people with diabetes, should try to eat enough dietary fiber because it has potential health benefits.

However, fiber is especially important for people with diabetes because it can help slow the digestion and absorption of carbs (4).

This can reduce blood sugar spikes and improve overall blood sugar management (5).

One way of determining how a carb-containing food will affect blood sugars is by looking at its glycemic index (GI).

The GI ranks foods based on how much and how quickly they raise blood sugar levels.

The scores run from 0–100 with the following classifications:

• Low GI: 55 or less
• Medium GI: 56–69
• High GI: 70–100

Diets based on low GI foods are thought to be particularly good for people with type 2 diabetes (6, 7, 8, 9).

This is because low GI foods are absorbed more slowly and cause a gradual rise in blood sugar levels rather than a large spike.

Overall, bananas score low to medium on the GI scale (42–62, depending on the ripeness) (10).

Summary

In addition to sugar and starch, bananas contain some fiber. This means the sugars in bananas are more slowly digested and absorbed, which could prevent blood sugar spikes.

The amount of this type of carbs in a banana varies depending on the ripeness.

Green, or unripe, bananas contain less sugar and more resistant starch (11, 12).

Resistant starches are long chains of glucose (starch) that are “resistant” to digestion in the upper part of your digestive system (13).

This means they function similarly to fiber and won’t cause a rise in blood sugar levels.

They also may help feed the friendly bacteria in your gut, which has been linked to improved metabolic health and better blood sugar management (4, 14, 15, 16).

In fact, a 2015 study on blood sugar management in women with type 2 diabetes found some interesting results. In an 8-week period, those supplementing with resistant starch had better blood sugar management than those who didn’t supplement (17).

Other studies have indicated that resistant starch may have beneficial effects for people with type 2 diabetes, such as improving insulin sensitivity and reducing inflammation (18, 19, 20, 21).

The role of resistant starch in type 1 diabetes is less clear.

A banana’s effect on blood sugar depends on its ripeness

Yellow, or ripe, bananas contain less resistant starch than green bananas, as well as more sugar, which is more quickly absorbed than starch.

This means fully ripe bananas have a higher GI and will cause your blood sugar to rise faster than green unripe bananas (12).

Summary

Green (unripe) bananas contain resistant starch, which doesn’t raise blood sugar levels and may improve long-term blood sugar management. Yellow (ripe) bananas contain more sugar, so they may cause a bigger rise in blood sugar.

Ripeness isn’t the only factor when it comes to the amount of sugar in your banana — size also matters. The bigger the banana, the more carbs you will be getting.

This means a larger banana will have a greater effect on your blood sugar level. This portion-size effect is called the glycemic load.

Glycemic load is calculated by multiplying the GI of a food by the number of carbs in a serving and then dividing that number by 100.

A score of less than 10 is considered low, 11–19 is medium, and 20 or more is high.

Bananas vary in size, from about 18.5–35 grams.

If a banana is fully ripe (with a GI of 62), then its glycemic load could range from 11 for a very small banana to 22 for a very large banana.

To ensure that your blood sugar doesn’t rise too much, it’s important to be aware of the size of the banana you’re eating.

Summary

The size of the banana you eat determines its effect on your blood sugar level. The larger the banana, the more carbs you’ll consume and the greater the rise in your blood sugar will be.

Most general dietary guidelines for diabetes recommend following a healthy, balanced diet that includes fruit (22, 23, 24).

This is because eating fruits and vegetables has been linked to better health and a lower risk of conditions such as heart disease and some cancers (25, 26, 27, 28).

People living with diabetes are at an even greater risk of these diseases, so eating enough fruits and vegetables is important (29, 30, 31, 32).

Unlike refined sugar products such as candy and cake, the carbs in fruits like bananas come with fiber, antioxidants, vitamins, and minerals.

More specifically, bananas provide fiber, potassium, vitamin B6, and vitamin C. They also contain some antioxidants and beneficial plant compounds (33).

For most people with diabetes, fruits — including bananas — are a healthy choice.

However, some people who are following low carb diets need to watch their total carbohydrate intake to stay within their daily carb allotment. This means foods higher in carbs, including bananas, have to be limited on low carb diets.

If your doctor says you can eat bananas, it’s important to be mindful of the ripeness and size of a banana to reduce its effect on your blood sugar level.

Summary

Fruits like bananas are healthy foods that contain fiber, vitamins, and minerals. You can include bananas in your diet even if you have diabetes. Check with your healthcare team before changing your eating plan.

If you have diabetes, it’s possible to enjoy fruit such as bananas as part of a healthy eating plan.

If you enjoy bananas, the following tips could help minimize their effects on your blood sugar levels:

• Watch your portion size. Eat a smaller banana to reduce the amount of sugar you eat in one sitting.
• Choose a firm, nearly ripe banana. Pick a banana that’s not overly ripe so that the sugar content is slightly lower.
• Spread your fruit intake throughout the day. Spread out your fruit intake to help reduce the glycemic load and keep your blood sugar levels stable.
• Eat them with other foods. Enjoy your bananas with other foods, such as nuts or full fat yogurt, to help slow the digestion and absorption of the sugar.

If you have diabetes, remember that carb-containing foods can affect people’s blood sugars differently.

Therefore, you might want to monitor how eating bananas affects your blood sugar and adjust your eating habits accordingly.