Popular smoothie ingredient may reduce one key health benefit, study suggests

Bananas are a smoothie staple, but a viral social media video has raised questions about whether they could reduce the nutritional benefits of other ingredients, such as blueberries.

In a July appearance on the "Mel Robbins Podcast," Dr. Rhonda Patrick, a biomedical scientist and founder of FoundMyFitness, demonstrated how she likes to make her smoothies, which do not include banana.

Bananas contain polyphenol oxidase (PPO), an enzyme that can break down polyphenols, which are beneficial for gut, heart and brain health, according to Patrick, who is based in San Diego. PPO is also responsible for turning cut fruit brown.

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Recent studies suggest that when a banana is added to a blueberry smoothie, fewer beneficial polyphenols are absorbed from the berries.

Instead, Patrick uses avocado to give the smoothie the same creamy texture with 95% less sugar, she said. Avocado also adds more vitamins and monounsaturated fat, which can increase absorption of carotenoids, like lutein and zeaxanthin, from kale in the smoothie.

This opinion sparked debate in the online nutrition community, with some dietitians and nutritionists arguing that bananas should not be villainized based on a small body of research.

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The study Patrick referenced, which was published in the journal Food & Function in 2023, analyzed food absorption in eight healthy men.

On separate days, participants drank either a banana smoothie (high in an enzyme called polyphenol oxidase), drank a mixed berry smoothie (low in the enzyme) or took flavan-3-ol capsules (dietary supplements that contain concentrated plant compounds) with milk.

Blood tests showed that people absorbed about 84% fewer beneficial plant compounds after drinking the banana smoothie than after taking the flavan-3-ol capsules.

While researchers didn't test a banana-blueberry smoothie, the results suggest that bananas could reduce the benefits of foods high in flavan-3-ols.

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Los Angeles-based registered dietitian nutritionist Ilana Muhlstein, author of the upcoming book "Beyond the Shot," said the findings are "interesting," but don't tell the whole story.

"It doesn't mean the smoothie loses all of its health benefits," she said. "You're still getting fiber from the banana, and many other beneficial nutrients from polyphenol-rich fruits."

Muhlstein pointed out that the study included only eight participants and has not yet been replicated. She also noted that researchers used a standardized cocoa-derived flavanol supplement instead of whole fruits, such as berries, which may be absorbed differently by the body.

In a follow-up post on Instagram, responding to the backlash from the original post, Patrick said, "You can add bananas to your blueberry smoothies. However, you should know that you are going to degrade some of the polyphenols in those blueberries."

"Bananas are nutritious, I eat them, and this is not a reason to stop," she added in the caption. "But if your goal is to preserve as many of the berry polyphenols as possible, the chemistry matters."

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Not every beneficial compound in blueberries will be eliminated by bananas, Patrick wrote, as the fruit contains many other polyphenols, including anthocyanins.

"This was a small study that should be replicated," she said. "But the magnitude of the effect was meaningful enough for me to consider when optimizing my smoothie."

New York-based certified holistic nutritionist Robin DeCicco agreed that the findings don't mean everyone should avoid bananas.

Unlike well-established advice to limit processed meats and added sugar, the guidance on bananas is more nuanced and doesn't apply to everyone, she told Fox News Digital.

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As nutrition advice spreads on social media, DeCicco said it's important to remember that everyone's health needs are different and to consult a doctor before following online recommendations.

The broader issue, she noted, is that Americans aren’t eating enough nutrient-rich foods, like bananas and berries, and are instead consuming more processed foods that have been linked to chronic disease.

"That’s why Americans are fatter and sicker than they've ever been, so I think focus on that more," DeCicco advised. "It doesn't need to be so complicated all the time … If you're eating a banana instead of french fries, that's good."

Nutrition should be individualized, DeCicco said. Someone who eats mostly fast food should focus on replacing processed foods with fruits and vegetables, while someone with a more advanced nutrition plan may benefit from limiting high-carb, high-sugar fruits like bananas.

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For those trying to lose weight and balance blood sugar, choosing fruits that are lower in sugar and higher in fiber may help with these outcomes.

"It really [depends] on where you're coming from and what your health journey is," DeCicco said.

Those looking to maximize polyphenol intake can swap bananas for frozen zucchini, avocado or Greek yogurt in smoothies for the same creamy texture, Muhlstein added.

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DeCicco shared the following simple, high-protein smoothie recipes that can be made at home.