Bananas and Plantains

TL;DR. The banana is a giant herb, not a tree, and its fruit is a sterile clone propagated by cutting for centuries. Every export banana on Earth is essentially the same plant, which is why a soil fungus destroyed the entire trade once already and is currently doing it again. Nutritionally a banana is a convenient package of potassium, vitamin B6, and a starch that converts to sugar as it ripens, so a green one and a spotted one are metabolically different foods. Plantains are the same genus eaten as a starchy staple, and they feed far more people than dessert bananas do.

1. What it is

Musa species, mostly hybrids of Musa acuminata (the A genome) and Musa balbisiana (the B genome). The dessert banana is triploid AAA; most plantains are AAB or ABB.

The plant is a giant herbaceous perennial, the largest flowering herb on Earth. What looks like a trunk is a pseudostem made of tightly wrapped leaf bases; there is no wood. The true stem is an underground corm, and new plants ("suckers" or "pups") emerge from it.

Botanically the fruit is a berry. Commercial bananas are parthenocarpic and sterile: they develop without fertilisation and contain no viable seeds, which is why the little black specks are aborted ovules rather than seeds. Wild bananas are full of hard, pea-sized seeds and are barely edible.

Don't be confused: banana and plantain is a culinary distinction, not a botanical one. There is no clean genetic line between them. In most of Latin America and Africa, the split is starchy-cooking versus sweet-dessert. In South and Southeast Asia, where hundreds of cultivars exist, the distinction barely makes sense.

2. Where it comes from

Origin: Southeast Asia and New Guinea, with archaeological evidence of banana cultivation in the Kuk Swamp of Papua New Guinea dating back roughly 7,000 years, making it one of the oldest domesticated crops. It spread westward through the Indian Ocean to Africa (Austronesian seafarers carried it to Madagascar and thence inland), and to the Americas with Portuguese and Spanish traders in the sixteenth century.

The modern export trade was built in the late nineteenth century by companies like United Fruit, whose political influence in Central America gave the world the phrase "banana republic." It is one of the few fruits whose history is genuinely a political history.

Who grows them now (approximate, FAO):

Uganda, Rwanda, Ghana, and the Democratic Republic of Congo are among the largest plantain and cooking-banana producers, where they are a genuine calorie staple: per capita consumption in parts of Uganda exceeds 200 kg a year.

3. How it is grown

Climate. Strictly tropical to subtropical: 26 to 30 °C ideal, and growth stops below about 14 °C. Frost kills. Needs 1,800 to 2,500 mm of rainfall a year or heavy irrigation, and high humidity. No chilling requirement, which is the reason it is available year-round.

Soil. Deep, well-drained, fertile loam, pH 5.5 to 7.0. Bananas are exceptionally hungry for potassium (a hectare removes hundreds of kilograms a year) and nitrogen. Waterlogging is fatal, and Panama disease is a soil-borne fungus, so drainage matters twice.

Wind is the great enemy. The pseudostem is soft and the leaves are enormous; a strong wind shreds the leaves (reducing photosynthesis) or topples the whole plant. Hurricanes routinely destroy entire national crops, which is a structural feature of the Caribbean banana economy.

The plant's life cycle is unusual and worth understanding:

1. A sucker is planted, or tissue-cultured plantlets are used (now standard for disease-free stock).
2. It grows for 9 to 12 months, producing 30 to 40 leaves.
3. The flower stalk emerges from the centre of the pseudostem and bends downward.
4. Female flowers develop into fruit, arranged in "hands" of 10 to 20 fingers, with 5 to 15 hands per bunch. A bunch weighs 30 to 50 kg.
5. The pseudostem fruits once and dies. It is cut down after harvest.
6. A selected sucker from the corm becomes the next plant, and the cycle repeats. A single corm ("mat") can crop for 10 to 30 years.

Management. Bunches are covered with perforated blue polythene bags to protect from insects, wind scarring, and spray, and to raise temperature slightly. Plants are propped with poles or twine because a loaded bunch will topple them. De-suckering keeps one follower per mat.

Disease is the defining issue. Black Sigatoka, a leaf fungus, requires spraying up to 40 to 50 times a year in wet tropical conditions, which is among the most intensive fungicide programmes in agriculture and a serious occupational exposure issue. Panama disease (Fusarium wilt) is the existential one, covered below.

Harvest and shipping. Cut deep green at about 75 percent maturity, washed, cut into clusters, boxed, and moved into refrigerated ships at 13 to 14 °C in a low-ethylene controlled atmosphere. Two to four weeks later, at the destination, they enter sealed ripening rooms and are dosed with ethylene at 15 to 20 °C for 24 to 48 hours, then delivered at whatever point on the seven-stage colour scale the retailer ordered (Chapter 8).

4. What is inside it

Per 100 g of raw dessert banana (a medium banana is about 118 g peeled):

Vitamin B6 is the standout, and it is under-advertised relative to potassium: one banana supplies roughly a quarter to a third of the daily requirement.

Potassium is over-advertised. A banana has about 400 mg, which is good and not exceptional: a baked potato has roughly double, and so do a cup of white beans, a cup of cooked spinach, or a serving of dried apricots.

Ripeness transforms it. As a banana ripens, amylase converts starch to sugars:

So a green banana is a slow-release resistant starch food and a spotted one is a fast sugar food. The calorie count barely changes; the metabolic behaviour changes a great deal.

Plantains, per 100 g raw: about 122 kcal, 32 g carbohydrate (mostly starch), 2.3 g fibre, 499 mg potassium, and notably 1,127 IU of vitamin A activity from carotenoids, which dessert bananas lack. Cooked, they behave like potatoes.

5. What it does in your body

The banana's practical properties come from three things.

Ripeness-dependent carbohydrate. Green banana starch is largely resistant starch type 2, which passes to the colon and is fermented into short-chain fatty acids (Chapter 14). Green banana flour is used clinically in some settings for exactly this. Ripe banana is quick fuel, which is why it is the standard cycling and running snack.

Potassium and blood pressure. Potassium counteracts sodium's effect on blood pressure by promoting sodium excretion and relaxing vessel walls (Chapter 16). A banana contributes about 10 percent of a day's need.

Pectin and resistant starch for bowel function. Bananas are a component of the traditional BRAT diet (bananas, rice, apple sauce, toast) for diarrhoea, and there is genuine evidence: green banana or banana flour has been shown in trials in Bangladesh to reduce the duration of persistent diarrhoea in children, via short-chain fatty acids promoting sodium and water absorption in the colon.

Not a serotonin source for your brain. Bananas contain tryptophan and small amounts of serotonin and dopamine. Serotonin does not cross the blood-brain barrier, and the tryptophan dose is small relative to a mixed meal's other amino acids, which compete for the same transporter. The "bananas make you happy" claim is not supported by any mechanism that works.

6. What the evidence actually shows

Established: bananas are a good source of B6 and a useful source of potassium, fibre, and rapidly available energy. Green banana resistant starch is fermented and produces SCFAs.

Strong: the general association between whole fruit intake and lower cardiovascular disease and type 2 diabetes risk includes bananas. The potassium-blood pressure relationship is well established at the nutrient level.

Mixed: green banana for diarrhoea in children has good trial support in specific settings; generalisation is less clear.

Thin to absent: claims that bananas improve mood, prevent cramps specifically, or aid sleep. The cramp claim is worth its own note: exercise-associated muscle cramps are now generally attributed to neuromuscular fatigue rather than to electrolyte depletion, and trials of electrolyte supplementation for cramps are unimpressive. Eating a banana for cramps is harmless and probably not doing what people think.

7. Who should eat more, who should be careful

Good for: endurance athletes (a banana performs about as well as a sports drink for carbohydrate during exercise, with fibre and potassium included), children, people with low potassium intake, and anyone who needs a portable food with no packaging problem.

Be careful if:

• Chronic kidney disease, stage 3 and above. Damaged kidneys cannot excrete potassium efficiently and hyperkalaemia causes dangerous cardiac arrhythmias. Bananas are among the first foods restricted. This applies also to people on ACE inhibitors, ARBs, or potassium-sparing diuretics (Chapter 75).
• Latex-fruit syndrome. People allergic to natural rubber latex frequently cross-react to banana, avocado, kiwi, and chestnut, because of structurally similar chitinase proteins. Reactions can be serious.
• IBS. Ripe bananas are higher in FODMAPs (fructose and fructans increase with ripening); unripe bananas are lower and are permitted on low-FODMAP protocols. This is the reverse of what most people assume.
• Diabetes. Fine in whole form; prefer a firmer, less ripe banana, and pair with protein or fat.
• Migraine. Bananas are on some trigger lists (tyramine), with weak evidence.

Ages. Excellent early weaning food from around 6 months: soft, sweet, no preparation, no common allergen. Whole raw banana pieces are soft enough not to be a major choking hazard, unlike apple. Good throughout life; particularly useful for older adults with poor appetite or chewing difficulty.

8. When and how to eat it

• Match ripeness to purpose. Green to yellow-green for slow energy and resistant starch; fully yellow for eating; spotted for baking, smoothies, and freezing.
• Before or during endurance exercise is where it shines: portable, rapidly absorbed, with potassium and B6.
• Pair with protein or fat (nut butter, yoghurt) to blunt the glucose rise, especially for a very ripe banana.
• Freeze overripe bananas peeled for smoothies and baking. Do not freeze them in the skin unless you enjoy dealing with the result.
• Plantains must be cooked. Green plantain fries as tostones or chips; yellow-black ripe plantain fries sweet as maduros; both boil and mash like potato.
• The peel is edible and eaten in parts of South Asia in curries, particularly the tender inner peel of young fruit. It is high in fibre and potassium. Wash it thoroughly given the spray regime.

9. Choosing, storing, and ripening

Choosing. Buy at the ripeness you need in the next few days, since they move fast. Avoid fruit with a bruised or split skin, or with a grey, dull cast, which indicates chilling injury. Green tips with a yellow body is normal.

Storing. This is the classic case where the fridge is wrong.

• Never refrigerate unripe bananas. Below about 13 °C they suffer chilling injury: the peel blackens and, more importantly, the ripening enzymes are damaged so the fruit never ripens properly. It stays starchy inside a black skin.
• Once fully ripe, the fridge is fine and useful: the peel will blacken cosmetically while the flesh holds for several more days.
• Bananas emit a lot of ethylene. Keep them away from anything you do not want ripened. This is the single biggest cause of a fruit bowl going over all at once.
• Separating the fingers and wrapping the crown in cling film slows ripening a little, by limiting ethylene release from the cut stem. The effect is real and modest.

Ripening. Put them in a paper bag, with an apple if you are impatient. Warmth speeds it.

10. The varieties worth knowing

The Cavendish problem. Every Cavendish banana is a genetically identical clone, so a pathogen that beats one beats all of them. Tropical Race 4 of Fusarium oxysporum f. sp. cubense does exactly that: identified in Taiwan in the 1990s, it has spread through Southeast Asia, Australia, the Middle East, Mozambique, and reached Colombia in 2019 and Peru in 2021. It lives in soil for decades, spreads on boots, tools, and water, and there is no fungicide for it. This is precisely the same failure mode that destroyed Gros Michel, running a second time with full advance warning.

The responses in progress: quarantine and biosecurity, conventional breeding of resistant hybrids (slow, because the plants are sterile), tissue-culture selection, and a genetically modified Cavendish carrying a resistance gene from a wild banana, which was approved in Australia in 2024. Whether consumers accept a GM banana when the alternative is no banana is about to be tested in public.

11. Myths and confusions

• "Bananas are the best source of potassium." Moderate at best. Potatoes, beans, spinach, dried apricots, and avocado all beat them per serving.
• "Bananas are radioactive and dangerous." They contain potassium-40, as does all potassium, including the potassium inside you. The "banana equivalent dose" is a teaching device for putting radiation figures in context, not a hazard. Your own body's potassium gives you far more.
• "Bananas cause constipation." Unripe ones can, through tannins and resistant starch. Ripe ones generally do not.
• "Bananas are fattening / too sugary." About 105 kcal for a medium fruit, with fibre. Whole fruit intake is associated with lower diabetes risk, not higher.
• "Bananas help you sleep." The melatonin and magnesium doses are small. No good evidence.
• "Green bananas are unripe and inferior." They are a different food with a different and arguably better metabolic profile.

12. The bottom line

• The banana is a giant sterile herb, propagated by cutting, and the entire export trade is a single clone facing a soil fungus with no cure. This is the most fragile major food supply chain on Earth.
• Nutritionally: notable for vitamin B6, useful for potassium and fibre, and metabolically transformed by ripeness. Green is slow-release resistant starch; spotted is quick sugar.
• Never refrigerate an unripe banana; refrigerate a ripe one. Keep them away from everything else in the fruit bowl.
• Plantains are the same genus as a starch staple and feed far more people than dessert bananas do. They need cooking.
• Restricted in advanced kidney disease and a common cross-reactant in latex allergy.

Sources and notes

Composition figures are from USDA FoodData Central; production figures are approximate FAOSTAT values for the early 2020s. Kuk Swamp domestication evidence is Denham et al., Science, 2003. Cultivation practice, bunch management, and Black Sigatoka spray intensity follow FAO and Bioversity International banana documentation. The Gros Michel collapse and Tropical Race 4 spread follow Ploetz's reviews in Phytopathology and Plant Disease and FAO's TR4 reporting; the GM Cavendish approval in Australia was announced by OGTR in 2024. Ripening room protocols and the seven-stage colour scale are industry standard. Green banana starch composition changes with ripening follow Zhang et al.'s resistant starch analyses. Green banana for persistent childhood diarrhoea is Rabbani et al., Gastroenterology, 2001, from Bangladesh. Latex-fruit syndrome follows Blanco's reviews. Exercise-associated cramp aetiology follows Schwellnus' neuromuscular fatigue work, which displaced the electrolyte explanation. Potassium restriction in CKD follows KDIGO guidance.

Open questions. Whether a resistant-starch-rich green banana diet has meaningful metabolic benefits beyond its fibre contribution has not been established in well-powered trials. Whether TR4-resistant GM or conventionally bred cultivars will be commercially accepted in time is genuinely unknown.

👉 Next: citrus, which includes the one fruit that can genuinely kill you through a drug interaction.