• Posted November 8, 2025

Want a Healthier Smoothie? New Study Says Skip the Banana

If a healthy slurp is your aim, skip the banana when you whip up a smoothie.

Researchers at the University of California-Davis found that adding banana may interfere with absorption of powerful compounds called flavanols, which are linked to brain and heart health.

"We were really surprised to see how quickly adding a single banana decreased the level of flavanols in the smoothie and the levels of flavanol absorbed in the body," lead author Javier Ottaviani said in a news release. He’s an adjunct researcher at UC-Davis and director of the Core Laboratory at Mars Edge, part of Mars Inc.

Flavanols —  which are found in such foods as apples, berries, cocoa and grapes — are natural compounds that help support memory, reduce inflammation and improve blood flow when consumed regularly. 

That is, unless banana or another ingredient get in the way, researchers say.

The problem is an enzyme abundant in bananas called polyphenol oxidase (PPO). In experiments, banana-based smoothies dramatically cut flavanol absorption compared to berry-based ones, researchers reported recently in the journal Food and Function.

They wanted to learn whether the same enzyme activity that quickly causes a banana or apple to turn brown when peeled affected how much of these beneficial flavanols the body absorbs when the fruits are combined in a smoothie.

"We sought to understand, on a very practical level, how a common food and food preparation like a banana-based smoothie could affect the availability of flavanols to be absorbed after intake," Ottaviani said. 

Participants in the study enjoyed two different smoothies. 

One was made with banana, which has high-PPO activity; the other was made with mixed berries, which have low-PPO activity. 

Participants also took a flavanol capsule for comparison. Afterward, flavanol levels in their blood and urine were measured.

The results were clear: Folks who drank the banana smoothie had 84% lower flavanol levels than those who swallowed the control capsule.

The Academy of Nutrition and Dietetics recommends consuming 400 to 600 milligrams of flavanols each day for cardiometabolic health. 

If you’re shooting to reach that level, go heavy on the berries when your smoothie is made of ingredients like pineapple, oranges, mango or yogurt — and skip the banana!

Ottaviani said the findings could open the door to more research on how food prep affects nutrient absorption.

Tea, for instance, is a major dietary source of flavanols, and how it is brewed could affect levels of the compounds available for the body to absorb.

The study was funded by a grant from Mars Inc., which helps researchers study the potential health benefits of cocoa flavanols.

More information

Good Housekeeping has a guide to making healthy smoothies.

SOURCE: University of California-Davis, news release, Oct. 27, 2025