Do Bananas Cancel Antioxidants? Decoding the Viral Smoothie Myth

According to a 2023 study from the University of California, Davis, a banana can reduce the absorption of certain antioxidants called flavanols by as much as 84% when blended with other flavanol-rich fruits. This surprising finding launched a viral debate, causing many to question, do bananas cancel antioxidants?

Quick Summary

Recent research reveals that bananas contain an enzyme, polyphenol oxidase (PPO), which can significantly reduce flavanol absorption when blended. However, the overall nutritional impact is often misunderstood.

Key Points

• PPO is the culprit: Bananas contain polyphenol oxidase (PPO), an enzyme that can break down certain antioxidants called flavanols, especially when blended.

• Reduced flavanol absorption: A 2023 study showed that adding a banana to a smoothie reduced flavanol absorption by as much as 84%, particularly when combined with berries or cocoa.

• Context is key: This effect was observed in blended foods. Eating bananas and flavanol-rich fruits separately or in whole form likely minimizes this interaction.

• Bananas remain healthy: Despite the PPO effect, bananas are still an excellent source of beneficial nutrients like potassium, vitamin C, and dietary fiber.

• Diversity is most important: Dietitians agree that a varied diet is more critical for overall health than micromanaging the nutrient absorption of a single meal.

• Optimize your smoothie: For maximum flavanol intake, combine berries with low-PPO fruits like pineapple, mango, or oranges, or add a splash of lemon juice.

• Don't overthink it: If you enjoy a banana and berry smoothie, the small reduction in specific antioxidants does not outweigh the overall nutritional benefits of consuming more fruit.

The Science Behind the Viral Claim: Polyphenol Oxidase (PPO)

The notion that bananas cancel antioxidants stems from the activity of a specific enzyme found naturally in the fruit called polyphenol oxidase (PPO). PPO is the same enzyme responsible for causing fruits and vegetables, like apples, pears, and avocados, to turn brown when they are cut and exposed to oxygen. In the context of a smoothie, this enzyme comes into contact with other compounds, including the health-promoting flavanols found in ingredients like berries and cocoa.

The UC Davis Study and Flavanol Absorption

This phenomenon was the subject of a specific study published in the journal Food & Function in 2023. Researchers investigated how bananas affected the absorption of flavanols in smoothies. The study involved a small group of healthy men who drank different smoothies and a control capsule.

• The Findings: Participants showed an 84% lower level of flavanol metabolites in their blood after drinking a banana-based smoothie compared to the control group.
• The Mechanism: The PPO from the banana rapidly breaks down the flavanols in the blended mixture, both before and after consumption, significantly limiting the amount that the body can absorb.

Putting the Study in Perspective: Is It a Big Deal?

While the study's results are interesting from a food science perspective, dietitians and nutritionists caution against overreacting. The conclusion that you should never combine bananas with berries is an oversimplification. A balanced perspective considers the broader context of a healthy diet and the limitations of the research.

The Limitations of the Research

• Small Sample Size: The study involved only eight male participants, making it difficult to generalize the findings to the entire population, including women or those with different metabolic profiles.
• Focus on a Single Compound: The research focused exclusively on flavanols. It did not conclude that bananas destroy all antioxidants or other nutrients.
• Blended vs. Whole Foods: The effect was observed in blended fruit. It is unclear if eating a whole banana and a handful of berries separately would have the same impact on absorption.

Bananas Still Offer Significant Health Benefits

Removing bananas from your diet entirely to avoid this one interaction would be counterproductive, as you'd lose out on other valuable nutrients. Bananas are an excellent source of:

• Potassium, which supports heart health and fluid balance.
• Vitamin B6, important for brain development and immune function.
• Vitamin C, a powerful antioxidant in its own right.
• Dietary fiber, which aids digestion and promotes a feeling of fullness.

A Comparison of PPO Levels in Common Smoothie Ingredients

Ingredient	PPO Activity Level	High in Flavanols?	Dietary Consideration
Banana	High	No	Combine with low-PPO fruits or consume separately from high-flavanol foods.
Berries (e.g., Blueberry, Strawberry)	Low	Yes	Excellent choice for antioxidant-rich smoothies.
Pineapple	Low	No	A great substitute for bananas to add sweetness and texture to berry smoothies.
Mango	Low	No	A low-PPO fruit that adds tropical flavor and creaminess.
Cocoa/Dark Chocolate	Low	Yes	The ideal pairing with low-PPO fruits for a flavanol boost.
Avocado	High	No	Use with caution in high-flavanol smoothies due to high PPO activity.
Spinach	Low	Yes	An excellent, low-PPO addition to any smoothie.

How to Maximize Antioxidant Absorption from Your Smoothies

If your primary goal is to maximize flavanol intake, there are simple strategies you can use without giving up your favorite fruits. Nutrition isn't about micromanaging every single meal but rather about making informed choices.

1. Pair Smarter: When making a smoothie with flavanol-rich ingredients like berries, cocoa, or apples, use low-PPO fruits as your creamy base. Options include pineapple, mango, oranges, or yogurt.
2. Separate Your Consumption: If you can't live without your banana-and-berry blend, consider eating them separately. Enjoy a banana as a snack before or after your flavanol-rich smoothie.
3. Add a Splash of Citrus: Ascorbic acid (Vitamin C) from citrus fruits like lemon or orange juice can help inhibit PPO activity. Adding a squeeze can help protect the antioxidants in your smoothie.
4. Use Frozen Fruit: The freezing process can slow down enzymatic activity. Using frozen bananas and berries might be beneficial, and it also eliminates the need for ice.
5. Consume Immediately: The degradation of flavanols by PPO begins as soon as the fruit is blended. Drinking your smoothie right away minimizes the window for this chemical reaction to occur.
6. Avoid Long Blending Times: High blending speeds can generate heat, which further speeds up the oxidation process. Blending just enough to achieve the desired consistency is best.

Conclusion: The Balanced Takeaway on Bananas and Antioxidants

So, do bananas cancel antioxidants? The answer is more nuanced than a simple yes or no. In blended foods, a banana's PPO enzyme can significantly reduce the bioavailability of specific antioxidants called flavanols from other ingredients. However, this is not a reason to eliminate bananas from your diet. Bananas are a nutritious food with many health benefits, including being a source of vitamin C, an antioxidant itself. The key takeaway is to be mindful of certain food combinations, particularly in smoothies, if maximizing flavanol absorption is a top priority. For the average person, focusing on a diverse intake of fruits and vegetables is far more important than worrying about a single food interaction.

You can read the original research paper on the RSC Publishing website.

Frequently Asked Questions

What is polyphenol oxidase (PPO)?

Polyphenol oxidase (PPO) is a naturally occurring enzyme found in many fruits and vegetables, including bananas, that causes them to brown when exposed to oxygen. In smoothies, this enzyme can react with and degrade certain antioxidants like flavanols.

Which antioxidants do bananas affect?

Bananas specifically affect flavanols, a type of polyphenol found in foods like berries, grapes, cocoa, and tea. The effect on other antioxidants is not the same.

Does this happen if I eat the banana and berries separately?

While the effect is most pronounced when the foods are blended together, some studies suggest PPO can still reduce flavanol absorption even if consumed simultaneously but separately. However, eating them separately is still a better option than blending them if you want to maximize flavanol absorption.

Should I stop putting bananas in my smoothies?

No, it is not necessary to stop. While a banana can reduce flavanol absorption, it provides many other nutrients like potassium and fiber. The overall nutritional benefit of a fruit-packed smoothie is more important than focusing on one specific interaction.

What can I add to a smoothie to prevent antioxidant loss?

To preserve antioxidants, add a splash of lemon or lime juice, which contains ascorbic acid (Vitamin C) that inhibits PPO. You can also combine flavanol-rich fruits with low-PPO fruits like pineapple, mango, or oranges.

Are frozen bananas okay in smoothies?

Yes. The freezing process can slow down enzymatic activity, so using frozen bananas and berries may help mitigate the PPO effect to a small degree. Just be sure to consume the smoothie soon after blending.

What are some low-PPO fruits I can use instead of bananas?

Great low-PPO alternatives for smoothies include pineapple, mango, oranges, kiwi, and passionfruit. These can provide natural sweetness and creaminess without the high PPO activity.

Does blending itself destroy antioxidants?

Some nutrient loss can occur during blending due to heat and oxidation, but the effect is often minimal, especially with quick blending and immediate consumption. The specific interaction between PPO and flavanols is a separate and more significant factor.