‘A Mars bar in a yellow skin’: the truth about bananas

Harry Luke
Harry Luke
9 Min Read

Health experts have long sung the praises of the humble banana, and it’s no surprise. They’re readily available, count as one of your five a day, and at just around 90 calories per fruit, are packed with the essential mineral potassium, which scientists believe could be crucial in the battle against high blood pressure (a third of adults in England are thought to suffer from the condition.)

But is the popular fruit really such a health saviour? Telegraph readers are divided, and even Andy Murray – often seen munching one courtside – declared them “a pathetic fruit” which “isn’t even juicy”. He ate them, he said, because of “what they have in them”.

Interestingly, banana bonuses change depending on how ripe they are. “It’s fascinating to watch the different stages of the fruit develop and know it can make a difference to the health benefits reaped – or not,” says Penny Weston, the nutrition expert behind wellness platform MADE. “Barely ripe bananas have high fibre and low sugar. And while they can taste more bitter, high fibre is good for feeding gut bacteria and helping the process through the gut. Keeping your gut healthy is good for the rest of your body.”

It’s also worth remembering that “while a very ripe banana will be easiest for the gut to digest, this is because it has the least starch, and an overripe banana has the highest sugar and lowest fibre and vitamin content”.

So what are the pros and cons of making the fruit one of your five a day?

The pros

They’re packed with potassium for your heart health and blood pressure

“Bananas are a good source of potassium, with one banana containing 451mg (around 10 per cent of you daily needs),” says Weston.

They’re also low in sodium which, along with their high potassium content, helps to control high blood pressure.

They’re a surprisingly good source of vitamin C

We tend to reach for citrus fruits for vitamin C, but a medium-sized banana provides a respectable 10 per cent of your daily vitamin C needs.

Vitamin C is really important for bodies for a variety of reasons,” says Weston. “It helps with immunity and maintaining normal skin, bones and cartilage. It also helps protect our cells and keep them healthy, as well as helping with wound healing and supporting our body when absorbing iron.”

Bananas can help digestion

We all know the importance of fibre, and one medium banana provides around 10 to 12 per cent of your daily needs. “Traditionally bananas have been found to ease constipation, stomach ulcers and heartburn,” says Weston.

They give you energy

Bananas contain three natural sugars – sucrose, fructose and glucose – giving you a fat and cholesterol-free source of energy. The mix of carbs and potassium are useful for exercise performance and muscle growth.

“This makes them ideal for athletes and children, they’re great for breakfast as a midday snack or before and after sports,” says Weston. “They’re low calorie yet filling because of the aforementioned high-fibre content. They’re rich in magnesium too, and a variety of antioxidants, such as flavonoids, which may reduce the risk of heart disease.”

They could reduce your risk of cancer

One study led by experts at the Universities of Newcastle and Leeds and published in the journal Cancer Prevention Research suggested that unripened bananas could have important implications in reducing cancers in the upper part of the gut.

“There is some research to suggest that the starch found in an unripe banana can reduce the risk of some cancers by 60 per cent,” says Weston.

The cons

You can have too much potassium

“Excess potassium may occur if you eat too many bananas,” says Weston. “Having too much potassium in the body is called hyperkalemia.”

As one Telegraph reader – with mild kidney disease – noted, his consultant told him to avoid bananas as “even small amounts of potassium” can make kidney function worse. So if you have been diagnosed with reduced kidney function, it might be worth keeping an eye on your potassium intake.

Dr Tom Oates, an NHS consultant nephrologist says: “We do tell the advanced kidney disease and dialysis patients to be very careful of potassium.” He says that bananas, avocado and dried fruit are all high in potassium, so “safer bets would be apples, pears and small citrus fruits like satsumas”.

They can cause wind and bloating

“Some people may experience bloating or gas after eating a banana due to the sorbitol, a naturally occurring sugar alcohol that may act as a laxative,” explains Weston. “People who are not used to a high-fibre diet may also experience some discomfort after eating a banana, such as cramping and bloating.”

As one Telegraph reader observed: “I have a couple of bananas every day, I was aware they are not great for greenhouse gas emissions.” The less ripe the banana the harder it will be to digest.

They can spike your blood sugar

“This is because the carbohydrates are broken down into glucose,” says Weston. “I would recommend pairing your bananas with a full fat yoghurt to avoid this, or eating one after a balanced meal.

“If you have type 2 diabetes, bananas are OK to eat in moderation,” she adds.  “There is little evidence to suggest bananas can cause type 2 diabetes.”

Too many will make you fat

Yes, we are all constantly encouraged to consume more fruit, but like every food, overdo it and you will gain weight. As another Telegraph reader said, “bananas are basically Mars bars in a yellow skin. Obesity is the main cause of essential hypertension.”

Weston recommends limiting intake to “no more than two bananas a day”, adding:

“Bananas are a carbohydrate and contain sugar, so eating a lot of bananas and not pairing this with physical activity may lead to weight gain – but this is like most foods!”

Avoid them at bedtime

While they are clearly healthier than eating a biscuit with your evening cocoa, they are not the best snack to consume before bed it seems.

“Some experts suggest that a banana should be avoided before bed as it can cause restless sleep due to the high levels of melatonin (a sleep hormone) they contain, which can cause an imbalance,” says Weston. She does add, however, that if you do not personally find it affects your sleep, she would say it’s not a bad bedtime snack option as “a banana can be digested quickly”.

In conclusion…

Weston says that banana consumption is really an individual matter. “If you like them, then enjoy them,” she says, though she wouldn’t recommend eating more than two daily.

“Like any other food, you have to listen to your body and how it responds. If you personally find that eating them seems to disagree with you, or your digestive system, look at other ways to get the nutritional benefits they do clearly have.”


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Harry Luke is a Professor in University of Galway. Harry's journey has been marked by a relentless pursuit of knowledge, creativity, and a commitment to making a positive impact on the world around him.