Contents
What it is
The banana is the fruit of a large perennial herb. It looks like a tree, but the trunk is a column of overlapping leaf sheaths rather than wood, which is why the plant counts as a herb. It is native to Southeast Asia and grows in the tropics. The varieties sold for eating have been bred until the seeds are all but gone. Unripe, the fruit is starchy and barely sweet; as it ripens the starch converts to sugar and the flesh softens. Refrigeration blackens the skin, so bananas keep better at room temperature, and away from other fruit they ripen more slowly.
Scientific name Musa
Bananas change composition dramatically as they ripen. Green, they are largely starch, much of it resistant starch that resists digestion. As they yellow, that starch breaks down into sugars.
Same fruit, different glycaemic response, different effect on the gut. "Is banana good?" is less useful than "which stage of banana?"
Key benefits
- Nutrition data
Potassium supports blood pressure
About 400 mg in a medium banana. Potassium helps excrete sodium and lowers vascular tension, which matters most in a diet already high in salt.
- Moderate evidence
Green banana resistant starch feeds the gut
Resistant starch escapes absorption in the small intestine and reaches the colon, where it feeds beneficial bacteria and supports production of short-chain fatty acids like butyrate. Ripening reduces it.[1]
- Nutrition data
It is rich in vitamin B6
One banana covers around 25% of an adult's daily requirement. Vitamin B6 is needed for amino acid metabolism and neurotransmitter synthesis.
- Nutrition data
A practical fuel around exercise
A ripe banana digests quickly and delivers sugars and potassium together. Trials found it matched sports drinks as a carbohydrate source during exercise.
How to eat it well
- Pick underripe if blood sugar is the concern, ripe if you want quick energy.
- Pair it with nuts or yoghurt to flatten the glucose response.
- Frozen banana works well in smoothies and loses almost nothing nutritionally.
- Black spots on the peel mean peak sweetness and minimum resistant starch.
- Refrigeration blackens the skin but slows ripening of the flesh.
How to read the grades
Each benefit carries a label showing how far research on people supports it. Grades differ between items even within the same ingredient.
- Nutrition data
- A fact verifiable from food composition databases or health authorities. This is a different kind of statement from a clinical effect.
- Strong evidence
- Consistently confirmed across randomised controlled trials or meta-analyses.
- Moderate evidence
- Human studies exist, but effect sizes are small or results are mixed.
- Early research
- Cell or animal work, or small preliminary studies.
- Not established
- Commonly claimed, but not confirmed in studies on people.
What to watch out for
- If you restrict potassium for chronic kidney disease, portion carefully.
- There is sugar here, so if you manage blood glucose, settling on about one a day is sensible.
- Latex allergy can produce a cross-reaction.
- In migraine-prone people, tyramine is occasionally a trigger.
Nutrition
Approximate values per 100 g edible portion.
- Calories
- 89 kcal4%
- Carbohydrates
- 22.8 g8%
- Fiber
- 2.6 g9%
- Sugars
- 12.2 g
- Protein
- 1.1 g2%
- Potassium
- 358 mg8%
- Vitamin B6
- 0.37 mg22%
- Vitamin C
- 8.7 mg10%
- Magnesium
- 27 mg6%
Percentages are of the US FDA Daily Value for adults and children 4 and over. National reference intakes differ by sex and age.
Calculate this alongside other ingredients →
Key nutrients
Dishes with this ingredient
Compare with
Sources
The databases and health authorities this article's nutrition figures and health statements draw on.
