Bananas have notoriously gotten a bad reputation for being too high in sugar, but in truth, they don't necessarily contain a much higher concentration than other fruits. "What we always want to look at first is carbohydrates, which break down into glucose (the fancy word for sugar) in the body," says Alix Turoff [1], a registered dietitian, nutrition consultant, and personal trainer. According to Turoff, you can expect to find about 27 grams of carbs in a medium-sized banana (of around 118 grams).
Although carbs are often the first thing banished from your diet, if you're trying to lose weight [2], carbohydrates that are valuable provide the most readily available source of energy. "A banana contains endless benefits in the form of essential vitamins and minerals, such as potassium, calcium, manganese, magnesium, iron, folate, niacin, riboflavin, and B6," says Bonnie Taub-Dix, RDN, the author of Read It Before You Eat It, Taking You From Label To Table [3].
Health Value
The majority of us don't get enough potassium, a nutrient that impacts the way our muscles function, including our hearts. "One medium-sized banana supplies only 105 calories and contains no fat (for those that are still fat-phobic)," says Taub-Dix.
Fibre
One banana provides around 3 grams of fibre, so although the fruit could be constipating for some people, its fibre might prove to be beneficial for others. "For those who have diabetes, it's interesting that the carbohydrates in unripe, green bananas contain something called resistant starch, which may help stabilise blood sugar levels," says Taub-Dix. "If you're counting calories, a banana snack is a great option as it provides a satisfying, rich taste and a creamy texture without creaking the calorie bank," says Taub-Dix. But if you're watching your blood sugar, be sure to eat a ripe banana along with some protein, like a tablespoon of almond butter or some cottage cheese, to slow up the absorption of the carbohydrates.
Carbs
Let's take a look at a medium banana. "It has 27 grams of carbohydrates and 3 grams of fibre," says Turoff. "If we take those 27 grams and substract 3 from the fibre, we get a net carbohydrate number of 24 grams. That means that 24 grams of carbs in this banana will be converted into sugar in the body." Net carbohydrates [5] calculated by taking the amount of total carbs and subtracting dietary fibre is said to be a more accurate way of determining how carbs will affect your blood sugar level and weight gain or loss.
Sugar
That same banana, however, contains 14 grams of sugar. This means that there are 14 grams of naturally occurring fructose or fruit sugar. Add to that the 24 net carbohydrates and you have one "sugary" fruit.
So Are Bananas Good or Bad For You?
It depends on your personal goals and needs. "If you're on a ketogenic diet [6], a banana would not be a good choice. If you eat 200 grams of carbs per day, then you definitely have room for a banana in your diet," says Turoff. "They are a great source of potassium and also deliver a quick supply of carbohydrates to the body so they make a great pre-workout snack."