Smoothies are a convenient way to pack in fruits, veg, and health-boosting compounds like flavanols, but bananas contain high levels of the enzyme polyphenol oxidase (PPO) that rapidly breaks down these flavanols. A controlled study found banana-based smoothies reduced flavanol absorption by up to 84%, and even having them separately only mitigated the loss to 37–41%. While bananas remain nutritious (potassium, fibre, vitamins), anyone aiming to maximise flavanol intake should swap in low-PPO bases like avocado, mango, or Greek yogurt. A simple six-step template helps you craft targeted smoothies for heart, brain, muscle, or gut health without sacrificing texture or flavour. Ultimately, variety and informed choices, not strict avoidance, are key to nourishing, delicious blends.

• Banana PPO Interference: Bananas are rich in polyphenol oxidase, which degrades flavanols from berries, cocoa, and tea both in the blender and in the stomach.
• Study Findings: In trials with eight healthy men, banana smoothies cut flavanol absorption by 84% versus a capsule control, and even separate sipping only reduced absorption by 37–41%.
• Balance of Benefits: Despite this interaction, bananas still offer potassium, fibre, resistant starch, and micronutrients, making them valuable for energy and recovery.
• Low-PPO Alternatives: Avocado, frozen mango, Greek yoghurt, silken tofu, chia seeds, and oats provide creaminess without harming flavanol content.
• Six-Step Smoothie Blueprint: Define your goal, choose a creamy base, add a flavanol “hero,” boost with fibre/fats, select a liquid, and finish with flavour enhancers.
• Recipe Example: For flavanol boost plus gut support: ½ avocado + 1 cup frozen mango, ½ cup mixed berries + 1 tbsp cocoa, 1 tbsp chia + 1 tbsp almond butter, 200 ml almond milk, sprinkle of ginger.
• Practical Nutrition: No single smoothie makes or breaks health – focus on consistent variety and tailor blends to your personal goals.

Smoothies are a popular choice for busy morning breakfasts, snacks or for post-exercise refuelling. They provide a quick and easy way to pack in fruit, vegetables, seeds, nuts, protein powders and more. A ripe banana is often the star ingredient, lending natural sweetness and a smooth, creamy texture.

Yet recent research suggests that this common choice may interfere with how our body absorbs some of the very nutrients we seek. So, having read the the landmark study, in this post I peel back the layers of the science and provide some context. So that, you can decide if you need to change your favourite smoothie recipes.

The key finding is that bananas contain high levels of an enzyme that breaks down flavanols from other smoothie ingredients like berries and cocoa. This doesn’t make bananas “bad” foods, but it does suggest we might want to think more carefully about when and how we use them.

I will share some easy swaps. These swaps are just in case it is important for you to preserve every last bit of nutrition. Finally, I share a simple, step-by-step blueprint to help you craft smoothies that fit your health goals.

By the end you will know why your blend tastes just as good without missing out. And, how to tailor each recipe to heart, brain or gut health and why variety remains the secret to lasting well-being.

Flavanols are natural compounds found in many plant foods, particularly fruits, vegetables, and cocoa. You may have heard flavanols described as antioxidants. They belong to a larger family called flavonoids, which give many plants their vibrant colours and help protect them from environmental stress. These antioxidant compounds also help protect our cells from stress and damage. But flavanols offer more than a shield.

Heart Health

Research shows that regular intake of flavanols can support a healthy blood pressure and improve cholesterol levels. They work by relaxing the lining of blood vessels, aiding smoother blood flow. Over time this can help reduce the risk of heart-related conditions. A major review of clinical trials found that people who consumed flavanols regularly had measurable improvements in several markers of cardiovascular health.

Brain Health

Our brains rely on a network of tiny blood vessels to deliver oxygen and nutrients. Flavanols appear to help keep those vessels flexible and responsive, supporting memory, focus and overall mental sharpness as we age.

Where to Find Flavaonols

• Berries: Blueberries, raspberries and blackberries top the list. They blend easily and add vibrant colour.
• Cocoa or cacao powder: Unsweetened cocoa is rich in flavanols. A tablespoon can give your drink a chocolatey boost.
• Tea: Brewed green or black tea, cooled, can be an unusual but effective smoothie base.
• Apples and grapes: These fruits contain flavanols in their skins. Using whole fruit keeps you from missing out.

Flavanols are not essential like vitamins, but adding them to your diet may contribute to long-term well-being. While there is no official minimum or maximum daily flavanol requirement most of the research for health benefits suggests 400-600mg daily. To put this in perspective, a cup of mixed berries contains roughly 200-300 milligrams, whilst a tablespoon of cocoa powder provides about 100-150 milligrams.

Common smoothie ingredients rich in flavanols include berries (blueberries, blackberries, raspberries), apples, grapes, cocoa powder, and tea. This makes smoothies an excellent vehicle for increasing flavanol intake, provided we understand how different ingredients interact.

The key to this story is the enzyme polyphenol oxidase, or PPO for short. This enzyme is found throughout the plant kingdom and serves an important protective function for plants.

You’ve likely seen PPO in action without realising it. When you cut an apple and it turns brown, or when a banana develops those dark spots, that’s PPO at work. This browning process isn’t spoilage, it’s actually a sophisticated defence mechanism.

When a plant’s tissues are damaged, PPO gets released and quickly converts certain plant compounds into protective substances. These new compounds have antimicrobial properties that help shield the damaged area from harmful bacteria and fungi. The brown colour you see is actually a type of natural “bandage” that seals the wound.

This evolutionary strategy works brilliantly for plants, but it creates a problem for smoothie enthusiasts. The same process that protects plants can break down beneficial flavanols before our bodies have a chance to absorb them.

Different plants contain varying amounts of PPO. Bananas are particularly notable for their high levels of this enzyme. This means that when you blend a banana with flavanol-rich ingredients like berries or cocoa, the PPO from the banana can significantly reduce the amount of flavanols available for absorption.

The process happens quickly and doesn’t require the smoothie to turn brown to be effective. Even if you drink your smoothie immediately after blending, the enzyme continues working, breaking down flavanols both in the blender and after you’ve consumed the drink.

To understand the real impact of this enzyme interaction, researchers from California and the UK got together. They developed a study that would show exactly what happens when we combine bananas with flavanol-rich ingredients.

The research involved eight healthy men aged 25-60 who each tried different test drinks on separate occasions. This type of study design, where participants serve as their own controls, helps ensure that individual differences don’t skew the results.

The participants consumed three different preparations: a banana-based smoothie enriched with flavanols from cocoa extract, a mixed berry smoothie (berries are naturally low in PPO), and a flavanol capsule that served as the control to measure maximum possible absorption.

Each participant tried all three options on separate days. On each occasion, blood and urine samples were taken for several hours after consumption. The data collected provided information about actual absorption rather than relying on theoretical calculations.

The Surprising Results

Quite surprisingly the findings showed those who drank the banana-based smoothie had 84% lower flavanol levels than the control group. In effect, one banana contained enough polyphenol oxidase to destroy the vast majority of flavanols present in the drink.

Perhaps most importantly, the team tested whether drinking the smoothie quickly might prevent this interaction. In a follow-up experiment, participants alternately sipped plain banana smoothie and a separate flavanol-rich drink, so the ingredients only mixed for the first time in the stomach.

Even under these conditions, flavanol absorption was still reduced by 37-41%. Laboratory tests confirmed that the PPO enzyme was still active in the acidic environment of the stomach, continuing to break down flavanols after consumption.

This reveals that the interaction isn’t just about what happens in the blender. The enzyme continues working inside your body, making the choice of ingredients more important than the speed of consumption.

Before you make any drastic changes, let’s look at this further. While the findings of the study are quite dramatic, they don’t tell the complete story.

For one thing, all eight of the participants were healthy men. This is not unusual in research studies. But it means, we have to look at the results with a critical eye. Such a small number and similarity of participants means the results may not apply to everyone. Women, different age groups, and people with varying health conditions might respond differently.

The research also measured immediate absorption from a single smoothie, not long-term effects of regular consumption. We don’t know whether the body might adapt to this interaction over time, or whether the reduced absorption from one smoothie significantly impacts overall health.

It’s also worth noting that flavanols naturally have relatively low absorption rates. Even under ideal conditions, the body typically absorbs only 2-20% of consumed flavanols. The 84% reduction, whilst significant, represents a drop from an already modest baseline.

Many nutrition experts suggest that for generally healthy people eating a balanced diet, the occasional banana-berry smoothie is unlikely to have a major negative impact on overall health.

Why You Might Want to Keep Using Bananas

Bananas remain highly nutritious foods with well-documented health benefits. They are really great sources of potassium, which is an important mineral for heart health and blood pressure. A medium-sized banana provides about 450mg of potassium, a significant portion of daily needs. They also contain fibre, vitamin B6, vitamin C and manganese.

Green or slightly underripe bananas contain resistant starch, which acts like fibre in supporting digestive health and feeding beneficial gut bacteria.

The decision about including bananas should be based on your primary goals for that particular smoothie. If you’re specifically trying to maximise flavanol absorption, the science clearly suggests omitting the banana. But, for sustained energy, post-workout recovery, or just a convenient, nutritious meal, a banana is still an excellent addition.

You might also like my post:  Resistant Starch and Gut Health

Creamy Bases That Don’t Interfere

When maximising flavanol absorption is your priority, several ingredients can replace banana’s creamy texture without the high PPO activity.

Avocado tops the list for creating rich, creamy smoothies. Half an avocado provides luxurious texture with a neutral flavour that won’t overpower other ingredients. As a bonus, you’ll get heart-healthy monounsaturated fats, fibre, and potassium.

Greek yogurt adds creaminess with a slight tang whilst significantly boosting protein content. This makes smoothies more filling and turns them into more complete meals. Choose plain, unsweetened varieties to avoid added sugars.

Frozen mango is perhaps the closest direct replacement for banana. It blends into a sweet, creamy consistency and provides vitamins A and C. The study’s researchers specifically recommended mango as a low-PPO alternative.

Silken tofu offers a vegan option that creates incredibly smooth, custard-like texture. It has a neutral flavour and provides quality plant-based protein without affecting taste.

If its a thicker texture that you are after, then chia seeds can create a gel-like consistency, while ground oats provide body and sustained release energy.

Here is a simple six-step template. Use it to build a blend that suits your main goal without fuss:

1. Define your aim:
Heart and brain: Focus on flavanol sources such as berries and cocoa.
Muscle recovery: Include protein from Greek yoghurt or tofu.
Digestive health: Add fibre from chia seeds or oats.

2, Choose a creamy base:
Pick avocado, frozen fruit, yoghurt or tofu.

3. Add your nutrient hero:
Berries, cocoa powder, or brewed tea (chilled).

4. Boost with fibre and heart-healthy fats:
Chia seeds, ground oats, nut butters or hemp seeds.

5. Select your liquid:
Water, plant milk, dairy milk or coconut water. Adjust volume to reach your ideal thickness.

6. Flavour finishers:
A teaspoon (tsp) of vanilla extract, a pinch of cinnamon or a few mint leaves.

Example build:
Goal: Flavanol boost and gut support
Base: ½ avocado + 1 cup frozen mango
Hero: ½ cup mixed berries + 1 tbsp cocoa powder
Extras: 1 tbsp chia seeds + 1 tbsp almond butter
Liquid: 200 ml almond milk
Finish: Sprinkle of ground ginger

Blend until smooth, taste and tweak sweetness or thickness as needed. Keep a log of your favourites. Soon you will have a personal menu of blends for every mood and need.

By combining a clear understanding of food-enzyme interactions with simple, practical swaps, you can enjoy smoothies that are both delicious and fully nourishing. Bananas retain their place in a balanced diet, yet knowing when to choose low-PPO alternatives empowers you to squeeze every drop of benefit from flavanol-rich ingredients. Experiment confidently, honour your preferences and feel better naturally with blends designed just for you.

When your priority is maximising flavanol absorption for heart or brain health, the science supports using low-PPO alternatives like avocado, mango, or Greek yogurt. When you need quick energy, post-workout recovery, or simply want a convenient, nutritious meal, bananas remain excellent choices.

Remember that no single meal can determine your overall health. What matters most is the broader pattern of eating a wide variety of plant-based and other nutritious foods consistently over time. This flavanol research should be viewed as a tool for optimisation, not a source of dietary stress.

The goal isn’t perfection but rather making informed choices that support your individual health objectives. Understanding food interactions like this one helps you approach nutrition with knowledge rather than fear, building better meals from a position of confidence rather than confusion.

Ultimately, the best smoothie is one that you’ll actually drink regularly whilst supporting your health goals. Whether that includes bananas or not depends entirely on what you’re trying to achieve with that particular meal.