That creamy banana you toss into your blueberry smoothie may be sabotaging the drink's best nutrition, according to research from UC Davis scientists who discovered an unexpected chemical clash in the blender.
The culprit is an enzyme called polyphenol oxidase, or PPO, which bananas contain in high amounts. When bananas and flavanol-rich fruits like berries blend together, the enzyme dramatically reduces how much of those beneficial plant compounds your body actually absorbs, researchers found.
In a controlled study published in Food & Function journal, participants who drank banana smoothies had 84 percent lower flavanol levels in their blood compared to those who consumed flavanols from a capsule control. A mixed berry smoothie without banana produced flavanol absorption nearly identical to the control.
The enzyme that causes bananas to brown when cut or bruised apparently continues its work in the blender and even after consumption, researchers believe. Lead author Javier Ottaviani, who directs the Core Laboratory of Mars Edge, said the team was surprised by how quickly a single banana could tank flavanol availability.
Flavanols are natural compounds linked to heart and brain health, abundant in berries, apples, grapes, cocoa, and tea. The Academy of Nutrition and Dietetics recommends 400 to 600 milligrams daily for cardiometabolic benefits.
The implications for smoothie lovers are straightforward. If your goal is maximizing flavanol intake from berries or other nutrient-dense fruits, skip the banana or enjoy it separately. Instead, pair berries with low-PPO ingredients like pineapple, mango, orange, or yogurt to keep the drink sweet and creamy without the enzymatic interference.
Bananas remain a healthy food full of fiber and potassium. The research simply shows they are not the ideal partner for flavanol-focused smoothies. People can still enjoy banana smoothies when creaminess or potassium is the priority rather than maximum flavanol absorption.
The study tested only eight to eleven participants, so while the findings are intriguing and useful, nutrition experts caution against overreacting. Smoothies remain nutritious overall, especially within a varied diet. Individual digestion and eating patterns affect outcomes differently for each person.
Ottaviani noted the findings may extend beyond smoothies. Tea, another major flavanol source, could potentially be affected by preparation methods that alter how many bioactive compounds remain available for the body to absorb. The research opens questions about how food combinations and preparation affect nutrient delivery across everyday meals.
Author Jessica Williams: "This is the kind of practical nutrition detail that actually changes how people eat, not some abstract finding destined for journals only."
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