Surprising research reveals why you shouldn’t add bananas to your smoothies

May 24, 2026

Researchers found that adding bananas to berry smoothies can significantly reduce how many flavanols your body absorbs, because bananas have high levels of an enzyme called polyphenol oxidase that interferes with these plant compounds. In the study, the banana smoothie led to about 84% lower flavanol levels than the control, while a mixed berry smoothie did not have the same effect.

The main takeaway is not that bananas are unhealthy. Bananas still provide useful nutrients, but they may be a poor choice when your goal is to preserve flavanols from foods like berries, grapes, apples, or cocoa.

For a more flavanol-friendly smoothie, the researchers suggest pairing berries with ingredients that have low polyphenol oxidase activity, such as pineapple, oranges, mango, or yogurt. The study was small, so the results are best seen as a practical nutrition tip rather than a final rule for everyone. SD