How bananas affect diabetes and blood sugar levels

If you have diabetes, bananas can be part of a healthy eating plan. Some tips may help reduce blood sugar spikes, including selecting an almost-ripe banana and eating it with other foods.

Bananas contain carbs, which raise blood sugar

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 the body makes.

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, which is about 126 grams (g), contains 29 g of carbs and 112 calories. The carbs are in the form of sugar, starch, and fibre. A medium banana contains about 15 g of sugar (that’s roughly 4 teaspoons of sugar).

Bananas also contain fibre, which may reduce blood sugar spikes

In addition to starch and sugar, a medium banana contains 3g of fibre (recommended daily requirements are 30g).

Everyone, including people with diabetes, should try to eat enough dietary fibre due to its potential health benefits. 

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

This can reduce blood sugar spikes and improve overall blood sugar management.

One compromise in eating ripe bananas is swapping over to green (unripe) bananas which contain resistant starch.

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. 

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

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

They also may help feed the friendly bacteria in your gut, which has a link with improved metabolic health and blood sugar management. 

In fact, a small 2023 study of 17 adults with type 2 diabetes found that taking resistant starch, in the form of native banana starch, reduced fasting blood sugar and blood sugar spike. It also reduced hunger and increased feelings of fullness. 

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. 

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 (glycaemic index) and will cause your blood sugar to rise fasterthan green unripe bananas.

Portion size is important

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 levels. This portion-size effect is called the glycaemic load.

The carb content of bananas varies by size, from about 18.5 to 35g. 

Knowing the size of the banana you’re eating is important to ensure your blood sugar doesn’t rise too much.

Are bananas safe for those with diabetes?

Most general dietary guidelines for diabetes recommended following a healthy, balanced diet that includes fruit.

This is because eating whole fruits and vegetables has been linked to better health and a lower risk of conditions such as heart disease and some cancers. 

People living with diabetes are at an even greater risk of heart disease and some cancers, so eating enough fruits and vegetables is important. 

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

More specifically, bananas provide fibre, potassium, vitamin B6, and vitamin C. They also contain some antioxidants and beneficial plant compounds.

For most people with diabetes, fruits — including bananas — can be part of a healthy choice.

However, some people who are prescribed a low carb diet need to watch their total carbohydrate intake to stay within their daily carb allotment. This means limiting foods higher in carbs, including bananas, when following a very low carb diet.

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

What foods can people with diabetes eat freely?

It is important to eat a balanced diet with a variety of nutrient-rich foods in portion sizes appropriate for meeting individualised nutrition goals.

Low carbohydrate whole foods that have a minimal effect on blood sugar can be beneficial for people with diabetes. These include: 

• Non- starchy vegetables, like cabbage, cucumber, and leafy greens

• lean proteins, like chicken, fish, eggs, and tofu

• healthy fats, like walnuts, avocados, and flaxseeds

However, even though a food is low carb, it doesn’t mean it is OK to eat it in large amounts every day. A diet with little variety can lead to nutrition deficiencies. 

Recap

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 one 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 glycaemic load and keep your blood sugar levels stable.

• Eat alongside other foods: Enjoy your bananas with other foods, such as nuts or plain Greek yoghurt, 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.

Extracts taken from Helen West, RD from www.healthline.com