banana

That creamy, delicious banana might be sabotaging the health benefits of your morning smoothie. A groundbreaking new study reveals that adding a single banana can reduce your body’s absorption of heart-healthy flavanols by a staggering 84%.

But before you banish bananas for good, the real takeaway is more nuanced. It’s not that bananas are bad; it’s that smoothie combinations are a science. Depending on your health goals, your fruit choices can make or break your drink’s nutritional power.

The Enzyme to Blame: Polyphenol Oxidase (PPO)

Published in the Food & Function journal, researchers from the University of California, Davis, pinpointed the culprit: an enzyme called polyphenol oxidase (PPO).

You’ve seen PPO in action; it’s what causes bananas, apples, and other fruits to turn brown when exposed to air. In your smoothie, this enzyme doesn’t just affect color; it actively breaks down the precious flavanols before your body can absorb them.

Flavanols are bioactive compounds celebrated for their profound benefits to heart and brain health.

How the Study Unfolded

To get practical, real-world results, lead author Javier Ottaviani and his team designed a simple test:

1. Participants drank a smoothie made with banana (high in PPO).
2. They drank another smoothie made with mixed berries (low in PPO).
3. For a baseline, they also took a pure flavanol capsule.

By analyzing blood and urine samples, the researchers could see exactly how much flavanol was absorbed.

The “Shocking” Result

The finding was dramatic. The banana smoothie led to up to 84% lower flavanol levels in the body compared to the control.

“We were really surprised to see how quickly adding a single banana decreased the level of flavanols… This highlights how food preparation and combinations can affect the absorption of dietary compounds.” — Javier Ottaviani, Lead Author

The Verdict: Should You Stop Adding Bananas?

Not necessarily. This isn’t a call to eliminate bananas, which are packed with potassium, fiber, and energy-boosting carbs.

Instead, it’s about intentionality. Ask yourself: What is the primary goal of my smoothie?

• If your goal is to maximize flavanol intake for cardiometabolic health, skip high-PPO fruits like bananas and apples. Combine flavanol-rich foods (like berries, cocoa, green tea) with low-PPO fruits like pineapple, mango, oranges, or citrus.
• If your goal is quick energy, muscle recovery, or digestive health, the banana remains an excellent, nutritious choice.