Bananas are a popular smoothie ingredient, but claims that they might interfere with the nutritional benefits of other ingredients could make you think twice before tossing one in the blender. Here’s the scoop on whether bananas really make your smoothie less nutritious.
Depending on what you put into your smoothie, bananas could affect its antioxidant potential.
That’s because bananas contain an enzyme called polyphenol oxidase (PPO), which can block the absorption of flavanols, a type of antioxidant found in high amounts in fruits such as berries, grapes, and peaches, Javier Ottaviani, PhD, director of the Core Laboratory of Mars Edge, told Health.
A 2023 study Ottaviani co-authored—the source of bananas’ bad reputation as a smoothie addition—found that those who consumed a banana-based smoothie had, on average, 84% less flavanol absorption than those who had a berry-based smoothie or took a flavanol capsule.
However, more research is necessary to confirm these effects. That study included only eight participants, which Toby Amidor, MS, RD, CDN, owner of Toby Amidor Nutrition, PC, and Health Shots author, called “extremely small.”
Even if bananas do significantly reduce the absorption of some flavanols, Amidor noted they also contribute their own antioxidants. While perhaps not as rich in antioxidants as berries, for example, they do contain flavanols, polyphenols, vitamin C, and carotenoids—so a banana in your berry smoothie doesn’t necessarily make it antioxidant-free.
While bananas might reduce the antioxidant content of certain smoothies, they also offer plenty of nutritional value on their own.
For starters, bananas are famously rich in potassium, an electrolyte essential for nerve function, muscle contraction, and maintaining healthy blood pressure. “The majority of us don’t get enough potassium, and bananas are a good source,” Bonnie Taub-Dix, RDN, author of Read It Before You Eat It—Taking You from Label to Table, told Health. One medium banana contains 375 milligrams of potassium (8% of the Daily Value).
In addition, bananas “provide significant vitamin B6, which is key for immune function and fetal brain development,” said Jamie Mok, MS, RDN, a Los Angeles-based registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics.
Bananas’ fiber content is another noteworthy plus. A medium banana supplies around 2 grams of fiber, and less-ripe bananas contain more resistant starch, a type of fiber that feeds beneficial gut bacteria and promotes overall gut health, Mok told Health.
The good news: Ottaviani’s study didn’t show that bananas decreased any of these nutrients.
If you like to put bananas in your smoothies, Amidor said there’s no reason to stop. “With 90% of Americans not meeting their vegetable recommendations and 85% of Americans not meeting their fruit recommendations, I would not hold out any fruit or vegetable from being added to a smoothie,” she told Health.
Taub-Dix added that bananas’ creamy consistency usually makes smoothies extra appealing, potentially helping you consume more fruits and vegetables overall.
That said, if you’re concerned about flavanol absorption, there are some workarounds. Ottaviani suggested pairing flavanol-rich ingredients with another creamy base, like yogurt, instead of bananas.
Amidor, however, said alternating between adding bananas and leaving them out is a smart way to get plenty of flavanols over time. “When you consume a wide variety of food in this manner, then you should be getting the nutrients you need—which are typically averaged over a few days (not in one smoothie),” she said.
