You might think a banana in your berry smoothie is a nutritious addition, but recent research indicates that it could actually diminish some of the fruits’ health benefits. A team from the University of California, Davis discovered that incorporating a banana into a smoothie can lower the absorption of heart- and brain-healthy compounds found in berries by up to 84%.
Published in the journal Food & Function, the study attributes this reduction to an enzyme called polyphenol oxidase (PPO), which is plentiful in bananas. This enzyme interacts with beneficial compounds known as flavanols found in foods like berries, grapes, apples, and cocoa, which are associated with better heart and brain health.
“We wanted to see how the preparation of a common food, such as a banana-based smoothie, impacts the absorption of flavanols,” said lead researcher Javier Ottaviani from UC Davis.
In a small clinical trial, participants consumed two types of smoothies—one with bananas and another made solely of mixed berries, which contain less PPO. The results showed a significantly lower flavanol absorption with the banana smoothie compared to the berry one and flavanol capsules.
Ottaviani remarked, “We anticipated that PPO might impact flavanol levels, but we were taken aback by how quickly and profoundly the addition of just one banana lowered flavanol content in the smoothie.” He further noted that even consuming a banana alongside flavanols, but not in the same smoothie, still reduced flavanol levels in the body.
“It’s crucial to steer clear of combining flavanol-rich foods with items that brown quickly when cut, like bananas, avocados, and beet greens,” he advised.
When bananas are blended, PPO reacts with oxygen, breaking down flavanols. This browning process can continue during digestion, making fewer compounds available for the body to absorb.
The Academy of Nutrition and Dietetics suggests a daily intake of 400 to 600 milligrams of flavanols. To reach that goal, Ottaviani recommends pairing flavanol-rich fruits like berries with low-PPO foods such as pineapple, oranges, mango, and yogurt.
Although Ottaviani points out that bananas are indeed nutritious, he cautions that if your aim is to maintain flavanols in your smoothie, perhaps rethinking that banana is a good idea.
Dr. Parth Babsar, a family medicine physician from Georgia, emphasizes that variety is key to a healthy diet. He suggests switching between different smoothie ingredients, such as berries and bananas, to optimize nutrient intake.
Babsar also noted that other food combinations, like tea with iron-rich foods or too much calcium alongside iron, can affect nutrient absorption. “While each case might be small, these patterns can accumulate over time,” he added.
Researchers see potential in this study to prompt further exploration into how the way food is prepared influences nutrient absorption.
This research was conducted in collaboration with scientists from the University of Reading in the UK and King Saud University in Saudi Arabia, funded by a grant from Mars, a company known for its work in cocoa flavanol research. Ottaviani serves as the director of the Mars Edge Core Research Institute.
