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I thought bananas were healthy, but my trainer told me not to eat them. Why?

My trainer has told me to avoid bananas. He calls them a no-benefit fruit that don’t belong in my diet. What’s wrong with bananas? Aren’t they at least a source of potassium?


Bananas are a healthy source of carbs and rich in potassium – something you need when working out

Why do bananas get a bad rap? Perhaps because some people mistakenly think they are much higher in sugar, or carbohydrate, than other fruit. Not so.

How many calories are there in a banana?

A medium banana has 105 calories and 27 grams of carbohydrate. Not much more than many other types of fruit: 1 medium pear (103 calories, 27 gm carb), 1 medium apple (95 calories, 25 gm carb), 1 cup pineapple (82 calories, 21 gm carb) and 1 cup blueberries (84 calories, 21 gm carb).

Or maybe bananas are maligned because they're believed to have high glycemic index (GI), causing your blood sugar and insulin to spike quickly after eating one. False, again. Bananas are actually low on the GI scale, having a glycemic index value of 51. (Foods with a low GI cause your blood sugar to rise gradually, not quickly, after eating them. GI values less than 55 are considered low.)

So I have to disagree with your trainer.

How much potassium is there in a banana?

Bananas do have nutritional benefits, including their high potassium content. One medium banana has 422 milligrams of potassium – almost 10 per cent of a day’s worth – considerably more than a medium-sized apple (195 mg), orange (237 mg) or pear (212 mg).

In fact, bananas outrank almost all other types of fruit when it comes to potassium. Cantaloupe and honeydew melon have similar potassium counts with 440 and 426 mg a cup, respectively.

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Most people don’t get enough potassium in their diet largely because they don’t eat enough fruits and vegetables. Potassium helps maintain the body’s water balance. Higher potassium intakes may protect against high blood pressure by increasing the amount of sodium your kidneys excrete.

Potassium is critical for normal muscle, nerve and brain function. Adults and teenagers need 4,700 mg each day; children aged 1 to 3 require 3,000 mg, 4 to 8-year-olds need 3,800 mg and kids aged 9 to 13 should get 4,500 mg of potassium daily.

Are bananas a good post-workout snack?

Bananas are a good source of carbohydrate, which helps fuel your muscles for a workout. Eating a banana an hour before you exercise provides glucose (sugar) into your bloodstream which your muscles use for energy.

They also make a great post-workout snack. Their natural sugars are used to rebuild muscle glycogen (carbohydrate) stores, your muscles’ main energy source. And the potassium in bananas assists in the process of converting blood sugar into glycogen. (A post-workout snack should also include a source of protein to help repair muscle tissue.)

Bananas are also a source of fibre (3.1 grams each) and a good source of vitamin B6.


All fruit is good for you, bananas included. Include different types of fruit in your diet to consume a wider variety of vitamins, minerals and phytochemicals.

Leslie Beck is a registered dietitian in Toronto.

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