Understanding the Smoothie Science: The Role of Polyphenol Oxidase (PPO)
For many, a banana and berry smoothie is a go-to for a quick, healthy meal or snack. The creamy texture from the banana combined with the tart sweetness of berries seems like a perfect match. However, recent scientific findings have shed light on a fascinating, yet potentially frustrating, interaction that occurs when these two fruits are blended together. The issue centers on an enzyme called polyphenol oxidase, or PPO, which is abundant in bananas, as well as apples and pears.
PPO is the same enzyme responsible for the browning of a banana or apple when it's exposed to oxygen after being peeled or cut. While this is a normal process, a 2023 study revealed a more significant consequence in the context of smoothies. The study found that when bananas were blended with flavanol-rich berries, the PPO from the banana actively breaks down the flavanols, making them much less available for the body to absorb.
The Impact of PPO on Flavanol Absorption
Flavanols are a type of antioxidant found in berries, cocoa, and tea, and are linked to numerous health benefits, including improved cardiovascular and cognitive health. The research, which measured flavanol metabolites in participants' blood, found that those who drank a berry-banana smoothie had significantly lower levels of flavanol absorption compared to those who consumed berries alone. It's not that the smoothie becomes unhealthy; it's that a key benefit—the absorption of these specific antioxidants—is dramatically reduced. The good news is that bananas still provide fiber, potassium, and other vitamins, but their inclusion negates a major perk of adding berries.
How to Maximize Nutrient Intake from Your Smoothies
To ensure you're getting the most out of your fruit smoothies, especially the flavanols from berries, there are a few simple strategies you can employ. This doesn't mean you have to stop making smoothies or give up bananas entirely, but rather to be mindful of your food pairings.
- Pair Berries with Low-PPO Fruits: To preserve the flavanols in berries, combine them with fruits that have low polyphenol oxidase activity. Good options include pineapple, mango, and oranges.
- Consider Separating Your Fruit Intake: If you love both bananas and berries, simply consume them separately. You could have a berry smoothie in the morning and eat a banana as a snack later in the day. The PPO in the banana can still interfere with absorption even if consumed separately but close together, but separating by a few hours is a good strategy to maximize benefits.
- Add Citrus Juice: The acidity in citrus fruits like oranges and lemon can help inhibit the PPO enzyme, protecting the flavanols from degradation. Adding a splash of lemon juice to your berry-based smoothie can act as a natural inhibitor. Vitamin C also helps stabilize flavanoids.
- Include other antioxidant sources: Incorporate additional ingredients rich in other antioxidants to compensate for any potential losses. Options include spinach, kale, and other antioxidant-rich vegetables.
Comparison of Smoothie Combinations
| Feature | Banana & Berries | Berries & Pineapple | Berries & Orange Juice |
|---|---|---|---|
| PPO Activity | High (from banana) | Low | Low |
| Flavanol Absorption | Significantly reduced | Maximize absorption | Maximize absorption |
| Creaminess | High | Low to medium | Low |
| Nutrients | Potassium, Fiber, Berries' nutrients (reduced flavanols) | Vitamin C, Manganese, Berries' full nutrients | Vitamin C, Folate, Berries' full nutrients |
| Flavor Profile | Creamy, sweet, classic | Sweet, tropical, tangy | Tangy, bright, citrusy |
Can you eat bananas and berries together whole?
The research specifically focused on blended fruit, so eating them whole may not have the same immediate, detrimental effect. The act of blending exposes the PPO to a large surface area of the berries, accelerating the enzymatic reaction. While some reaction could still occur in the digestive system, it is likely far less potent than in a blended smoothie.
The Bigger Picture: Don't Panic
Dietitians emphasize that while this nutrient interaction is scientifically interesting, it should not cause anxiety about your diet. Most people get their nutrients from a variety of sources throughout the day, and one smoothie will not make or break your health. The findings are more relevant for those specifically trying to maximize their flavanol intake for a particular health goal. A varied and balanced diet remains the best approach to overall wellness. The occasional banana and berry smoothie is still a net positive for your health, providing fiber, vitamins, and minerals. It's about being strategic if you're targeting specific nutrients.
Conclusion: Navigating Smoothie Synergies
The question "does banana cancel out berries in a smoothie?" has a nuanced answer. While bananas themselves don't become "unhealthy," their high concentration of the enzyme PPO does significantly reduce the bioavailability of flavanols from berries when blended together. For those looking to maximize the antioxidant benefits of their berries, pairing them with low-PPO fruits like mango or pineapple is the best strategy. However, for most people, the occasional berry-banana blend is not cause for concern and still provides valuable fiber and nutrients. Ultimately, understanding these food synergies allows for more informed and intentional dietary choices, helping you get the most out of your healthy habits. For additional information on food synergies and optimizing nutrient intake, explore resources from reputable nutritional science institutions.
Visit the UC Davis news release for a direct source on the original research.
Frequently Asked Questions
What is polyphenol oxidase (PPO)?
PPO is an enzyme found in fruits and vegetables, like bananas, that causes browning when exposed to oxygen. In smoothies, it reacts with and breaks down flavanols, a type of antioxidant found in berries.
Does this mean my berry and banana smoothie is unhealthy?
No, it is not unhealthy. The smoothie still provides fiber, vitamins, and minerals. However, you are absorbing significantly less of the beneficial flavanol antioxidants from the berries than you would if you consumed them separately or with a low-PPO fruit.
Which fruits can I blend with berries to maximize antioxidant absorption?
To maximize flavanol absorption, blend berries with low-PPO fruits like pineapple, mango, oranges, or avocado. The low PPO activity in these fruits will not interfere with the antioxidants in the same way bananas do.
How much do bananas reduce flavanol absorption?
A 2023 study showed that combining bananas and berries in a smoothie can reduce the absorption of flavanols by up to 84%.
Should I stop putting bananas in my smoothies entirely?
Not necessarily. Bananas offer their own nutritional benefits, including potassium and fiber. If maximizing flavanol intake is not your primary goal for that particular smoothie, or if you eat a variety of other flavanol-rich foods, there is no need to completely eliminate bananas from your diet or smoothies.
Does cooking berries with bananas have the same effect?
Heat can denature enzymes like PPO, so cooking bananas and berries together (e.g., in a baked good) is less likely to cause the same level of flavanol degradation seen in a raw, blended smoothie.
Is it okay to eat whole bananas and whole berries together?
Yes, the effect is specific to the blending process. Eating whole fruits together is unlikely to cause the same significant reduction in flavanol absorption because the PPO and flavanols are not mixed and exposed to oxygen in the same way they are in a blender.
