A new study published in Food & Function suggests that adding bananas to berry smoothies may significantly reduce their nutritional value — particularly their flavanol content, a group of compounds linked to heart and brain health.
What’s the issue?
Bananas are a popular smoothie ingredient thanks to their flavor and creamy texture. They also offer fiber, potassium, and vitamin B6. However, bananas contain high levels of an enzyme called polyphenol oxidase (PPO) — the same compound that causes browning in cut fruit. When PPO interacts with flavanols (found in berries, cocoa, and certain fruits), it breaks them down, making them less available for the body to absorb.
Flavanols are important for maintaining cardiometabolic health and reducing the risk of conditions like heart disease, obesity, and diabetes. Studies have also shown flavanols offer anti-inflammatory, gut health, and neuroprotective benefits.
The study findings
Researchers from the University of California, Davis and the University of Reading tested the impact of banana smoothies versus berry smoothies on flavanol absorption in eight healthy men. Blood and urine samples revealed that participants who drank berry smoothies retained high levels of flavanols, while those who consumed banana-based smoothies had 84% lower flavanol levels.
Because the flavanol breakdown happens during smoothie preparation — not digestion — the study’s results likely apply to both men and women.
What to do instead
Lead author Dr. Javier Ottaviani says this doesn’t mean bananas are bad — just be cautious if you’re pairing them with flavanol-rich berries. Instead, try combining bananas with fruits that don’t interfere with flavanol absorption, like mango, pineapple, or oranges.
If you’re craving a berry smoothie but want to skip the banana, nutrition expert Carolyn Williams recommends swapping it with Greek yogurt and a bit of honey or mango for sweetness and creaminess.
The takeaway? Bananas are still a healthy option, but if you want the full benefit of berries’ flavanols, it’s best to skip them in the same blend.
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