Authored by a learner who has partially completed an ISSA course on Coursera.
Source: University of California, Davis.
Overview: Bananas are healthy. Berries are healthy. But blended together, the banana’s PPO enzyme can reduce flavanol absorption from berries by up to 84%, per UC Davis research. If your goal is maximizing antioxidant intake, swap the banana for mango, pineapple, or yogurt.
Yes — and the number will surprise you. Adding just one banana to a berry smoothie can reduce your body’s absorption of key antioxidants by up to 84%, according to new research from the University of California, Davis. Here is what is actually happening inside your blender, and what you should do about it.
84% lower flavanol absorption was recorded in people who drank a banana-berry smoothie compared to a plain berry smoothie — based on blood and urine analysis by UC Davis researchers. That is not a rounding error. That is most of the benefit, gone.
Smoothies feel like the easiest nutrition win of the day. Throw in some berries, add a banana for creaminess, blend, and done. But new research published in the Royal Society of Chemistry journal Food & Function, and covered by ScienceDaily in May 2026, reveals that this specific combination may not work the way most people think.
The problem is not the banana itself. Bananas are genuinely nutritious — rich in potassium, fiber, and complex carbohydrates. The problem is what the banana does to other ingredients the moment the blender starts running.
Bananas contain very high levels of an enzyme called polyphenol oxidase, commonly shortened to PPO. This is the same enzyme responsible for that familiar brown discoloration you see when you slice a banana or cut open an apple and leave it exposed to air.
What is PPO?
PPO is an enzyme that sits inside fruits and vegetables, minding its own business — until you slice, squash or blend them. When that happens, it activates and starts breaking down the healthy plant compounds around it. That browning thing you see on a sliced apple? That’s PPO at work. It’s the same thing in a blender, except you can’t see it. PPO destroys the flavanols from your berries before your body even gets to use them.
When you blend a banana with berries, that PPO enzyme is released from the banana’s cells and immediately begins interacting with the flavanols present in the berries. Flavanols — a subclass of flavonoids — are powerful plant compounds linked to heart health, better blood pressure, and cognitive function. They are exactly what most people drink berry smoothies to get more of.
What the UC Davis Study Actually Found
The researchers tested three different options at different times on the same group of people: a banana smoothie with cocoa flavanols, a mixed-berry smoothie with the same flavanols and a flavanol capsule used for comparison. After each test, they measured the levels of flavanols in the participants’ blood and urine for a number of hours. This helped them see how much of the flavanols were actually absorbed and used by the body.
“We were really surprised to see how quickly adding a single banana decreased the level of flavanols in the smoothie and the levels of flavanol absorbed in the body. This highlights how food preparation and combinations can affect the absorption of dietary compounds in foods.”
The berry smoothie was nearly as good as the flavanol capsule at helping the body absorb flavanols, suggesting it delivered the nutrients well. The banana smoothie, on the other hand, led to 84% less flavanol absorption. This was a very large drop and occurred just after the smoothie was blended .
In another part of the study, researchers kept the banana and the flavanols apart until the last moment, rather than mixing them together. Absorption of flavanol was still lower but the reduction was not so great. These results suggest that the PPO (polyphenol oxidase) in bananas may continue to act on flavanols even after the drink has been consumed, perhaps in the stomach. Thus, a change in the preparation of the smoothie alone may not entirely prevent the loss of flavanols.
Which Fruits Are High and Low in PPO?
The research team tested 18 different fruits and vegetables to measure their PPO activity levels. This gives us a practical way to think about smoothie ingredients beyond just the banana.
| Ingredient | PPO Activity | Effect on Flavanols |
|---|---|---|
| Banana | Very High | Significantly reduces absorption |
| Beets & Beet Greens | High | Reduces absorption |
| Pears | High | Reduces absorption |
| Blueberries | Very Low | No interference |
| Strawberries | Very Low | No interference |
| Mango | Low | Safe to combine |
| Pineapple | Low | Safe to combine |
| Oranges / Citrus | Low | Safe to combine |
Why Flavanols Actually Matter?
Maybe you are wondering whether it matters. The answer is, yes, if you drink smoothies for health. The Academy of Nutrition and Dietetics recommends 400–600 milligrams of flavanols daily to support heart and metabolic health. Flavanols are natural compounds that are found in foods like berries, grapes, tea, cocoa and apples. Research suggests they may support healthy blood flow, blood pressure and cholesterol levels and even support brain function.
The practical implication: If your smoothie is built around blueberries, blackberries, or cocoa powder because you want the cardiovascular and cognitive benefits of flavanols, then adding a banana may be quietly canceling out most of that benefit before you even finish the glass.
It is worth noting that the original study was small — eight participants in the first part, eleven in the second. That means the results are credible and well-designed, but not yet a final verdict for every person or every diet. Individual digestion varies, and the overall dietary picture always matters more than any single food combination.
What This Means for Your Smoothie Routine
This research does not mean you should stop eating bananas. It means you should be more intentional about when and how you use them. Think of it in two distinct goals:
| ❌ Avoid This Combo | ✅ Better Alternative |
|---|---|
| Banana + Blueberries | Berries + Mango |
| Banana + Cocoa Powder | Berries + Pineapple |
| Banana + Blackberries | Berries + Greek Yogurt |
| Banana + Grapes | Berries + Orange |
| Beets + Berries | Banana + Protein Powder (Solo) |
If you love the thick, creamy texture that bananas give a smoothie, that’s totally valid — just swap the berries for the purpose of that drink. Banana with protein powder, peanut butter and milk makes a perfectly solid post workout shake. It just shouldn’t be your daily flavanol strategy.
The Bigger Lesson Here
The UC Davis study is a good reminder that nutrition is not just about what you eat — it is about what your body can actually use. A smoothie is not simply a sum of its ingredients. When those ingredients interact inside a blender, or inside your digestive system, the chemistry changes. That can work in your favor or against it depending on the combination.
Journal Reference:
Ottaviani, J. I., Ensunsa, J. L., Fong, R. Y., Kimball, J., Medici, V., Kuhnle, G. G. C., Crozier, A., Schroeter, H., & Kwik-Uribe, C. (2023). Impact of polyphenol oxidase on the bioavailability of flavan-3-ols in fruit smoothies: A controlled, single-blind, crossover study. Food, 14(18), 8217. https://doi.org/10.1039/D3FO01599H
Disclaimer: This article is written for general informational and educational purposes only. The content shared here is based on published scientific research and is not intended to serve as medical or dietary advice. The findings discussed — including the UC Davis study on banana smoothies and flavanol absorption — reflect early-stage research conducted on a small group of participants, and results may not apply to every individual. Always consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, especially if you have an existing health condition.