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A viral video on social media suggests that blending bananas and berries together “kills” the nutritional value of the fruit before it reaches the bloodstream. The creators cite a real study, but as with most nutrition content online, the purpose of the video is to grab your attention. Is it a bad idea to mix fruit in a smoothie? It is worth walking through what the research actually says on this topic.
Flavan-3-ols are a type of polyphenol. Flavan-3-ols are found in foods like tea, cocoa, apples, pears, berries, and grapes. Regular intake has been linked to cardiovascular and cognitive benefits, and it’s recommended that people consume 400 to 600 milligrams per day. Because most people fall well short of recommended fruit and vegetable intake (and therefore polyphenol intake), smoothies are a commonly recommended way for folks to eat more fruits and vegetables.
The concern raised by the viral claim centers on an enzyme called polyphenol oxidase, or PPO. This enzyme is responsible for the browning that happens when you cut open an apple or banana and leave it exposed to air. PPO can chemically alter polyphenols, and researchers wanted to know whether the PPO activity triggered by blending fruit actually reduces how much flavan-3-ol the body absorbs.
The Study
In the study, eight healthy adult men consumed a banana smoothie, which is high in PPO activity, a mixed berry smoothie, which is low in PPO activity, and a control smoothie trial with a flavan-3-ol capsule. Each smoothie contained the same amount of a specific flavan-3-ol called epicatechin. Blood was drawn hourly over six hours to track how much of the flavan-3-ol compound made it into circulation. The banana smoothie produced peak blood concentrations that were significantly lower than the capsule control, while the berry smoothie performed similarly to the capsule.
It does suggest that pairing a high PPO fruit like banana with flavan-3-ol supplement may reduce how much of that specific compound you absorb compared to a lower PPO fruit combination. It’s also, importantly, a narrow finding. This does not mean you cannot mix blueberries and bananas, That is not what was tested. The study only tracked one flavan-3-ol, epicatechin, out of the many polyphenols found in whole foods. And the flavan-3-ol was added artificially to the smoothies rather than measured as it naturally occurs in the fruit itself. Bananas and blueberries were never mixed together. None of this makes the study wrong, but the concluding advice in the viral social media video… well it’s difficult to see how they got there, and even more difficult to see how that advice when only 12% of Americans consume enough fruit in their diets.
Are Smoothies Good for you?
Smoothies can be a great tool for some, and a detriment to others. Food form (i.e. solid, semi-solid, or liquid) can affect how much people eat. Liquids tend to be consumed faster and in larger quantities than solid foods with comparable calorie content. This is partly because liquids go down faster, and may not trigger the same satiety signals that solid food does. This means a smoothie loaded with nut butter, oats, and several servings of fruit can add up in calories faster than the same ingredients eaten whole, not because blending changes the underlying nutrition, but because it is simply easier to consume more of it quickly. This can be a benefit for athletes struggling to eat enough, and equally unhelpful for those athletes trying to be calorie-conscious. This is a far more relevant consideration for athletes rather than the potential loss of a single flavan-3-ol.
Does Blending Food Destroy the Fiber?
This myth doesn't hold up either. The physical amount of soluble and insoluble fiber in a blended fruit is chemically identical to the fiber in the whole fruit. Blending breaks up the structure but does not remove the fiber itself. In fact, in some cases, blending fruits like berries or passionfruit may make the nutrients in the seeds more available. In short, blending is not a bad thing.
The Takeaways
For athletes, the practical takeaway is this: Smoothies are not bad, and neither is mixing fruits together. Smoothies remain one of the more accessible ways to get more fruits and vegetables. Food is more than any single nutrient, and whole foods bring fiber, vitamins, minerals, and a range of polyphenols. If maximizing flavan-3-ol intake specifically is a personal goal, then this study may be relevant to you. But that is a refinement, not a reason to avoid smoothies altogether, and it should never come at the expense of simply eating more fruits and vegetables in whatever way is realistic and sustainable.
This is also a useful look into how nutrition claims spread online. A research study gets reduced to a single alarming headline, stripped of its details, limitations, and true conclusions. What starts as science becomes poor advice. If a claim about food sounds extreme, pause, because the research behind it is almost always more nuanced than the version that goes viral.
At Fuelin, we help athletes cut through the chaos. Our coaching and content are built on scientific research rather than the headlines. Our goal is translate that research into guidance you can actually use without getting pulled into fear-based rules. Whether the question is about smoothies, supplements, or how to structure your fueling around a big training block, our goal is to help you make decisions based on evidence rather than the current claims circulating social media.
Megan