Research from the University of California, Davis, has revealed that adding bananas to smoothies may hinder the body’s absorption of beneficial compounds known as flavanols. This finding was published in the Royal Society of Chemistry journal Food & Function.

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The study focuses on an enzyme called polyphenol oxidase (PPO), which is abundant in bananas. PPO activity can significantly lower the amount of flavanols that the body absorbs from other smoothie ingredients. Flavanols are plant compounds associated with heart and cognitive health and are present in foods like apples, pears, berries, grapes, and cocoa.

Javier Ottaviani, the lead author and director of the Core Laboratory of Mars Edge, explained that the research sought to understand how a common food preparation method, specifically banana-based smoothies, impacts flavanol availability. When fruit is cut or bruised, PPO triggers a browning reaction, and the team wanted to explore whether a similar process could affect nutrient absorption.

Participants in the study consumed a banana smoothie, a mixed berry smoothie with low PPO activity, and a flavanol capsule as a control. Blood and urine samples revealed that those who drank the banana smoothie had 84% lower flavanol levels compared to the control, while the mixed berry smoothie's flavanol absorption resembled that of the capsule.

The researchers also found that PPO activity might affect flavanol absorption in the stomach, as flavanol levels decreased even when the banana drink was kept separate from other ingredients until consumption.

The study does not suggest that bananas are unhealthy, as they are rich in fiber, potassium, and other nutrients. However, for those aiming to maximize flavanol intake, it may be advisable to avoid bananas when combining them with foods rich in flavanols like berries or cocoa. The Academy of Nutrition and Dietetics recommends a daily intake of 400 to 600 milligrams of flavanols for cardiometabolic health, which can be sourced from tea, apples, berries, and grapes.

For optimal flavanol absorption, Ottaviani recommends pairing flavanol-rich fruits such as berries with low PPO ingredients like pineapple, oranges, or yogurt. Bananas can still be enjoyed separately or in smoothies that do not prioritize flavanol content.

The study was small, involving eight participants in the first part and eleven in a subsequent test, prompting experts to advise caution in overgeneralizing the results. Smoothies with bananas can still be nutritious within a balanced diet. Ultimately, the research emphasizes that ingredient combinations can significantly influence nutrient absorption, suggesting that smoothies are more complex than simply blending together different foods.

The study also touches on broader research into flavanols and other plant bioactives, which are being investigated for their potential benefits in various health domains. Overall, these findings can inform better choices for those seeking to enhance flavanol intake in their diets.