Bananas are among the world’s most popular fruit.

They are highly portable and easy to consume, making them a perfect on-the-go snack.

Bananas are also fairly nutritious, and contain high amounts of fiber and antioxidants.

However, many people have doubts about bananas due to their high sugar and carb content.

This article takes a detailed look at bananas and their health effects.

Bananas Contain Several Important Nutrients

Over 90% of the calories in bananas come from carbs.

As the banana ripens, the starch in it turns into sugar.

For this reason, unripe (green) bananas are high in starch and resistant starch, while ripe (yellow) bananas contain mostly sugar.

Bananas also contain a decent amount of fiber, and are very low in protein and fat.

Many different types of bananas exist, which causes the size and color to vary. A medium-sized (118 grams) banana contains about 105 calories.

A medium-sized banana also contains the following nutrients (1):

  • Potassium: 9% of the RDI.
  • Vitamin B6: 33% of the RDI.
  • Vitamin C: 11% of the RDI.
  • Magnesium: 8% of the RDI.
  • Copper: 10% of the RDI.
  • Manganese: 14% of the RDI.
  • Fiber: 3.1 grams.

Bananas contain other beneficial plant compounds and antioxidants as well, including dopamine and catechin (2, 3).

For more details on the nutrients in bananas, this article contains everything you need to know.

Bottom Line:

Bananas are a good source of several nutrients, including potassium, vitamin B6, vitamin C and fiber. They also contain various antioxidants and plant compounds.

Bananas are High in Fiber and Resistant Starch

Fiber refers to carbs that cannot be digested in the upper digestive system.

High fiber intake has been linked to many health benefits. Each banana contains about 3 grams, which makes them a good fiber source (1, 4).

Green or unripe bananas are rich in resistant starch, a type of indigestible carbohydrate that functions like fiber. The greener the banana is, the greater the content of resistant starch (5).

Resistant starch has been linked to several health benefits (6, 7, 8, 9, 10, 11, 12):

  • Improved colon health.
  • Increased feeling of fullness after meals.
  • Reduced insulin resistance.
  • Lower blood sugar levels after meals.

Pectin is another type of dietary fiber that is found in bananas. Pectin provides structural form to bananas, helping them keep their shape.

When bananas become overripe, enzymes start to break down the pectin and the fruit becomes soft and mushy (13).

Pectins may reduce appetite and moderate blood sugar levels after meals. They may also help protect against colon cancer (14, 15, 16, 17).

Bottom Line:

Bananas are high in fiber. Unripe bananas are also rich in resistant starch and pectin, which can provide numerous health benefits.

How do Bananas Affect Weight Loss?

No study has investigated the effects of bananas on weight loss.

However, one study of obese, diabetic people investigated how unripe banana starch (high in resistant starch) affected body weight and insulin sensitivity.

They found that taking 24 grams of banana starch each day for 4 weeks caused weight loss of 2.6 lbs (1.2 kg), while also improving insulin sensitivity (18).

Other studies have also linked fruit consumption to weight loss. Fruit is high in fiber, and high fiber intake has been associated with lower body weight (19, 20, 21).

Moreover, resistant starch has received some attention recently as a weight loss friendly ingredient (22).

It may contribute to weight loss by increasing fullness and reducing appetite, thus helping people eat fewer calories (8, 23).

Although no studies have shown that bananas per se cause weight loss, they have several properties that should make them a weight loss friendly food.

That being said, bananas are not a good food for low-carb diets. A medium-sized banana contains 27 grams of carbs.

Bottom Line:

The fiber content of bananas may promote weight loss by increasing the feeling of fullness and reducing appetite. However, the high carb content of bananas makes them unsuitable for low-carb diets.

Bananas Are High in Potassium

Bananas are a major dietary source of potassium.

One medium-sized banana contains around 0.4 grams of potassium, or 9% of the RDI.

Potassium is an important mineral that many people aren’t getting enough of. It plays a crucial role in blood pressure control and kidney function (24).

A potassium-rich diet can help lower blood pressure and positively affect heart health. A high potassium intake is linked to a reduced risk of heart disease (25, 26, 27).

Bottom Line:

Bananas are high in potassium, which may help lower blood pressure and reduce the risk of heart disease.

Bananas Also Contain a Decent Amount of Magnesium

Bananas are a good source of magnesium, as they contain 8% of the RDI.

Magnesium is a very important mineral in the body, and hundreds of different processes need it to function.

A high intake of magnesium may protect against various chronic conditions, including high blood pressure, heart disease and type 2 diabetes (28, 29).

Magnesium may also play a beneficial role in bone health (30, 31, 32).

Bottom Line:

Bananas are a decent source of magnesium, a mineral that plays hundreds of roles in the body. Magnesium may protect against heart disease and type 2 diabetes.

Bananas May Have Benefits for Digestive Health

Unripe, green bananas are rich in resistant starch and pectin.

These compounds act as prebiotic nutrients, which feed the friendly bacteria in the digestive system (33).

These nutrients are fermented by the friendly bacteria in the colon, which generate butyrate (34).

Butyrate is a short-chain fatty acid that contributes to digestive health. It may also reduce the risk of colon cancer (35, 36).

Bottom Line:

Unripe, green bananas are rich in resistant starch and pectin, which may promote digestive health and reduce the risk of colon cancer.

Are Bananas Safe For Diabetics?

Opinions are mixed about whether bananas are safe for people with diabetes, since they are high in starch and sugar.

However, they still rank low to medium on the glycemic index, which measures how foods affect the rise in blood sugar after a meal.

Bananas have a glycemic index value of 42–62, depending on their ripeness (37).

Consuming moderate amounts of bananas should be safe for people with diabetes, but they may want to avoid eating large amounts of bananas that are fully ripe.

Furthermore, it should be noted that diabetics should always make sure to monitor their blood sugar levels carefully after eating foods rich in carbs and sugar.

Bottom Line:

Eating a moderate amount of bananas should not raise blood sugar levels significantly. However, diabetics should be careful with fully ripe bananas.

Do Bananas Have Any Negative Health Effects?

Bananas do not seem to have any serious adverse effects.

However, people who are allergic to latex may also be allergic to bananas.

Studies have shown that around 30–50% of people who are allergic to latex are also sensitive to some plant foods (38).

Bottom Line:

Bananas don’t seem to have any known negative health effects, but they may cause allergic reactions in some individuals with latex allergy.

Like Most Fruit, Bananas Are Very Healthy

Bananas are very nutritious.

They contain fiber, potassium, vitamin C, vitamin B6 and several other beneficial plant compounds.

These nutrients may have a number of health benefits, such as for digestive and heart health.

Although bananas are unsuitable on a low-carb diet and may cause problems for some diabetics, overall they are an incredibly healthy food.