Banana fruits are among the most important food crops in the world.
They come from a class of plants called Musa, that are native to Southeast Asia, and are grown in many of the warmer areas of the world.
Bananas are a healthy source of fiber, potassium, vitamin B6, vitamin C, and various antioxidants and phytonutrients.
There are many different types, and they come in many different sizes. Color usually varies from green to yellow.
One medium-sized banana contains about 105 calories, most of which come from carbs.
The table below contains detailed information on all the nutrients in bananas (1).
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Bananas are a rich source of carbohydrates, mainly starch in unripe bananas and sugars in ripe bananas.
The carbohydrate composition of bananas changes drastically during ripening.
The main component of unripe bananas is starch. Green bananas contain up to 70-80% starch, on a dry weight basis.
During ripening, the starch is converted into sugars and ends up being less than 1% when the banana is fully ripe (2).
The most common types of sugar found in ripe bananas are sucrose, fructose and glucose. In ripe bananas, the total content of sugars can reach more than 16% of the fresh weight (2).
Bananas have a glycemic index of 42-58, depending on their ripeness, which is relatively low (3). This is a measure of how quickly the carbs in a food enter the bloodstream.
The low glycemic index of bananas is explained by their high content of resistant starch and fiber, which mitigates the blood sugar rise after a meal.
A high proportion of starch in unripe bananas is resistant starch, which, as the name suggests, is resistant to digestion and is therefore a type of fiber.
Resistant starch passes down to the large intestine where it is fermented by bacteria in a process that forms butyrate, a short-chain fatty acid that appears to have beneficial effects on intestinal health (4).
Bananas are also a good source of other types of fiber, such as pectin. Some of the pectin in bananas is water-soluble.
When bananas ripen, the proportion of water-soluble pectin increases, which is one of the main reasons why bananas turn softer as they age (5).
Both pectin and resistant starch moderate the rise in blood sugar after a meal.
Bottom Line: Bananas are mainly composed of carbs. Unripe bananas may contain decent amounts of resistant starch, which functions like a fiber, promoting colon health and healthy blood sugar levels.
Vitamins and Minerals
Bananas are a significant source of several vitamins and minerals, especially potassium, vitamin B6, and vitamin C (1).
- Potassium: Bananas are a good source of potassium. A diet high in potassium can lower blood pressure in people with high blood pressure and has positive effects on cardiovascular health (6).
- Vitamin B6: Bananas are high in vitamin B6. One medium-size banana can provide up to 33% of the recommended daily intake of vitamin B6.
- Vitamin C: Like most fruit, bananas are a good source of vitamin C.
Bottom Line: Bananas contain a number of vitamins and minerals in decent amounts. These include potassium, vitamin B6, and vitamin C.
Other Plant Compounds
Fruits and vegetables contain numerous types of bioactive plant compounds, and bananas are no exception.
- Dopamine: Although it is an important neurotransmitter in the brain, dopamine from bananas doesn't cross the blood-brain barrier to affect mood, but rather acts as a potent antioxidant (7).
- Catechin: Several antioxidant flavonoids are found in bananas, most notably catechins (8). They have been linked to various health benefits, including a reduced risk of cardiovascular disease (9).
Bottom Line: Like other fruits, bananas contain several healthy antioxidants, which are responsible for many of their health benefits. These include dopamine and catechin.
Health Benefits of Bananas
Like most natural foods, bananas may have a number of health benefits.
Heart disease is the world's most common cause of premature death.
Bananas are high in potassium, a mineral that promotes heart health and normal blood pressure. One medium-sized banana contains around 0.4 grams of this heart-healthy mineral.
According to a large analysis of many studies, daily consumption of 1.3 to 1.4 grams of potassium is linked to a 26% lower risk of heart disease (10).
In addition, bananas contain antioxidant flavonoids that have also been associated with a significant decrease in the risk of heart disease (11).
Bottom Line: Bananas may be beneficial for heart health due to their high amount of potassium and antioxidants.
Unripe, green bananas contain considerable amounts of resistant starch and pectin, which are types of dietary fiber.
Resistant starch and pectins act as prebiotic nutrients, which support the growth of beneficial gut bacteria.
Bottom Line: Unripe bananas contain decent amounts of resistant starch, a type of fiber that may promote colon health.
Adverse Effects and Individual Concerns
There are mixed opinions on whether bananas are good for diabetics or not.
It is true that bananas are high in starch and sugar, and therefore one might expect them to cause a large rise in blood sugar.
But due to their low glycemic index, moderate consumption of bananas should not raise blood sugar levels nearly as much as other high-carb foods.
However, diabetics should avoid eating large amounts of well-ripened bananas. After eating foods rich in sugar and carbs, diabetics should always make sure to monitor their blood sugar levels carefully.
On a different note, people sometimes seem to consider banana consumption as a risk factor for constipation (14), while other studies indicate that bananas may actually have an opposite effect, at least in some people (15).
In conclusion, banana consumption does not seem to have any serious adverse effects, at least not when consumed in moderation.
Bottom Line: Bananas are generally considered healthy. However, high intake of well-ripened bananas should be avoided by diabetics.
Bananas are among the world's most commonly consumed fruits.
They are primarily composed of carbs, and contain decent amounts of several vitamins, minerals, and antioxidants.
Potassium, vitamin C, catechin, and resistant starch are among the healthy nutrients in bananas.
These may contribute to improved heart and digestive health when consumed regularly as a part of a healthy lifestyle.