Bananas may be sabotaging your smoothie's superpowers, scientists warn

Adding a banana to your berry smoothie might sound healthy, but new research suggests the popular combo could cancel out some of the fruit's benefits.

Scientists at the University of California, Davis, found that adding a banana to your smoothie could significantly reduce the absorption of the berries' heart- and brain-boosting compounds by as much as 84%.

The study, published this month in the journal Food & Function, points to an enzyme called polyphenol oxidase (PPO), which is abundant in bananas, as the reason for the drop. 

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PPO reacts with beneficial plant compounds known as flavanols — found in foods like berries, grapes, apples and cocoa — which are linked to a boost in heart and brain health.

"We sought to understand, on a very practical level, how a common food preparation like a banana-based smoothie could affect the availability of flavanols to be absorbed after intake," lead researcher Javier Ottaviani, an adjunct professor at UC Davis, told Fox News Digital.

In a small clinical study, volunteers drank two smoothies — one made with banana and another with mixed berries, which are low in PPO. Blood and urine samples showed that the banana smoothie had reduced flavanol absorption, compared to the berry version or a flavanol capsule.

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"While we anticipated that PPO might influence the flavanol content and absorption from smoothies, we were surprised by how quickly and significantly the addition of just one banana reduced flavanol content in the smoothie and, consequently, the levels of flavanols in the body," Ottaviani said.

"It was also surprising to find that even if bananas are consumed at the same time as flavanols, but not in the same smoothie, the PPO still reduced the levels of flavanols in the body," he added. 

"It is important to avoid combining flavanol-containing foods with ones that quickly turn brown after they are cut, like bananas, avocados and beet greens."

When bananas are blended, PPO reacts with oxygen and begins breaking down flavanols, the same process that causes fruit to brown after being cut. This can continue during digestion, leaving fewer of those compounds for the body to absorb.

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The Academy of Nutrition and Dietetics advises getting between 400 and 600 milligrams of flavanols daily. To meet that goal, Ottaviani said it's best to combine flavanol-rich fruits, like berries, with low-PPO ingredients such as pineapple, oranges, mangoes or yogurt.

"Nevertheless, bananas remain a great fruit and a great option for smoothie preparation, but not if aiming to maintain the flavanols in your smoothie," Ottaviani added.

Dr. Parth Bhavsar, a Georgia-based board-certified family medicine physician and founder of TeleDirectMD, said the key is diversity and fine-tuning your diet.

"Moderation and rotation are much more relevant," Bhavsar, who wasn't involved in the study, told Fox News Digital. "If you enjoy your bananas in a smoothie, go for it. But you could switch between making berry and banana smoothies."

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Other common food pairings can also interfere with nutrient absorption, Bhavsar noted. For example, tea or coffee can block iron uptake, calcium can compete with iron, raw cruciferous vegetables may hinder iodine absorption, and very high fiber intake can limit mineral absorption. 

"Although small in each instance, they can add up in patterns over time," he said.

The UC Davis researchers noted that the recent findings could spur more research into how food preparation affects nutrient absorption.

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The study, which was conducted along with scientists from the University of Reading in England and King Saud University in Saudi Arabia, was funded by a research grant from Mars, Inc., a frequent collaborator in cocoa flavanol research. Ottaviani is the director of the Mars Edge Core Laboratory.