Bananas 101: Calories, Nutrition, Allergies, and more

Calories  •  Carbs  •  Sugars  •  Nutritional value  •  Health benefits  •  Banana allergy

Nothing beats a banana as a quick snack when you’re feeling low on blood sugar. Still, many wonder about the calories in a banana, and if it’s fine to eat if you’re looking to lose weight.

A source of healthy carbs and potassium, bananas are rich in nutrients. This article explores the nutritional content of bananas, including their carbohydrate content, and some health benefits.

Calories in a banana

A medium banana is about 7 to 7 and a half inches long and weighs about 120 grams. It contains 105 calories on average or about 5% of the DV for a 2,000-calorie diet. However, this number may vary depending on its size (1).

• Extra small (less than 6 inches long, 81 grams): 72 calories
• Small (6 to 7 inches long, 101 grams): 90 calories
• Medium (7 to 8 inches long, 118 grams): 105 calories
• Large (8 to 9 inches long), 136 grams): 121 calories
• Extra large (9 inches or longer, 152 grams): 135 calories
• Per 100 grams: 89 calories

Most of a banana’s calories, nearly 90%, come from carbs, with about 4% coming from protein and 3-4% from fat. For every 100 grams, about 75 grams of a banana’s mass comes from water.

How many carbs are in a banana

Bananas are almost all carbs, making them a poor source of calories on a low-carb or keto diet.

Here’s the carbohydrate content for standard banana sizes (2):

• Extra small (less than 6 inches long, 81 grams): 18.5 grams
• Small (6 to 7 inches long, 101 grams): 23 grams
• Medium (7 to 8 inches long, 118 grams): 27 grams
• Large (8 to 9 inches long), 136 grams): 31 grams
• Extra large (9 inches or longer, 152 grams): 35 grams
• Per 100 grams: 22.7 grams

If you’re looking to calculate the “net carbs” in a banana, you simply subtract the fiber content from the total carbohydrate content (net carbs = total carbs – dietary fiber). Since fiber is not digested, it offers almost no calories.

The fiber content for standard banana sizes (3):

• Extra small (less than 6 inches long, 81 grams): 2 grams
• Small (6 to 7 inches long, 101 grams): 2.6 grams
• Medium (7 to 8 inches long, 118 grams): 3 grams
• Large (8 to 9 inches long), 136 grams): 3.5 grams
• Extra large (9 inches or longer, 152 grams): 4 grams
• Per 100 grams: 2.6 grams

Additionally, the carb content of bananas changes drastically after ripening. The main component of unripe bananas is starch. A large portion of this is resistant starch, which remains largely undigested and functions like fiber. Resistant starch provides several health benefits, including:

• aiding digestion
• promoting the growth of gut bacteria
• improves insulin resistance

During ripening, much of this starch is converted to sugar, reaching a much higher carb and sugar content. Therefore, it is much better to eat bananas in an unripe state, or when they have just started ripening.

Calories in a banana from sugars

About half the calories in a banana come from sugars, but this is not comparable to table sugar. In whole fruits, the sugars are digested and absorbed at a slower rate than added sugars. It is also rich in valuable nutrients.

Here’s the sugar content for standard banana sizes (4):

• Extra small (less than 6 inches long, 81 grams): 10 grams, 40 calories
• Small (6 to 7 inches long, 101 grams): 12 grams, 48 calories
• Medium (7 to 8 inches long, 118 grams): 14.5 grams, 58 calories
• Large (8 to 9 inches long), 136 grams): 16.5 grams, 66 calories
• Extra large (9 inches or longer, 152 grams): 18.5 grams, 75 calories
• Per 100 grams: 12 grams, 48 calories

While an average banana contains about 12 grams of sugar, it is not the same as eating 12 grams of granulated sugar. How quickly the carbohydrate enters your bloodstream is what shows how healthy it is.

The glycemic index (GI) gives a food a number up to 100, with a higher rating indicating quick absorption of the food and hence a quick spike in blood sugar. While table sugar has a GI of 63, bananas have a GI of 51, making them a much healthier carbohydrate to manage blood sugar levels, along with being nutrient-dense.

Bananas contain many other beneficial nutrients and minerals

Bananas are known for their potassium content, with one medium banana offering 422 milligrams of potassium, about 9% of the daily requirements.

A medium banana provides you with the following nutrients:

• Vitamin B6: 22% of the DV
• Vitamin C: 17% of the DV
• Manganese: 16% of the DV
• Potassium: 12% of the DV
• Magnesium: 8% of the DV
• Folate: 6% of the DV
• Riboflavin (vitamin B2): 5% of the DV

Bananas also provide small amounts of choline, a nutrient essential for liver and brain function.

Health benefits of bananas

Bananas are one of the most popular fruits among runners and endurance athletes for being rich in potassium while providing a quick hit of carbs. Here’s how they may benefit you:

• Diabetes and blood sugar management. Green bananas are high in resistant starch, which functions like dietary fiber. A systematic review found that green banana flour or pulp showed benefits in insulin metabolism and diabetes management (5).
• May improve heart health. Dietary potassium in bananas is one of the biggest reasons for their popularity. A study found that people who consumed adequate amounts of potassium had a lower risk of stroke, coronary heart disease, and other cardiovascular diseases (6).
• Wound healing properties. A study found that using banana peels on a wound decreased the level of swelling, providing some relief and quicker healing (7).

Bananas are also rich in antioxidants and resistant starch, making them beneficial for brain health, and degenerative illnesses, and delaying the effects of aging.

Adverse effects and banana allergy

While bananas are usually easy to digest, some people might find difficulty with their high fiber and resistant starch, especially when eating green bananas. They might experience constipation, but the body gradually gets used to this higher fiber intake. Drinking higher amounts of water can help with this.

In most regions, less than 1 percent of the population has a banana allergy (8), with the incidence estimated to be anywhere from 0.04 percent to 1.2 percent globally. The allergic reaction is caused due to specific proteins found in the bananas.

Symptoms usually begin within minutes and can range from mild to life-threatening. People usually experience the following symptoms:

• itchy mouth and throat
• a rash known as hives (urticaria)
• swelling of the skin (angioedema)

More serious symptoms are often referred to as the ABC symptoms, and can include:

• Swelling in the throat, tongue, or upper airways, causing difficulty in swallowing.
• Sudden wheezing, heavy breathing, and difficulty breathing.
• Dizziness, tiredness, confusion, or loss of consciousness.

This more serious reaction is known as anaphylaxis. A severe, potentially life-threatening allergic reaction, it can occur within seconds or minutes of exposure. If emergency treatment is not received, anaphylaxis can lead to death within half an hour.

In a nutshell

Bananas are a quick, healthy, and highly nutritious meal. I have always enjoyed a bowl of bananas with some peanut butter and honey, with sea salt sprinkled on top.

An average banana contains about 100 calories and 23 grams of carbs, making it a great option for a quick breakfast or a small snack.