No, Bananas Do Not Destroy the Nutrients in Your Smoothie.
Who doesn’t love bananas in a smoothie? They add sweetness and do wonders for texture. But not Rhonda Patrick, who proudly announced to her followers that she doesn’t add bananas to smoothies out of fear that they destroy the polyphenols in blueberries. This belief spread on social media a few years ago, and its truth has been greatly exaggerated. I’ll explain where this myth came from and what you really need to know.
Why do people think bananas are bad for smoothies?
The idea that bananas should be avoided in smoothies arose in 2023, when a study published in the journal Food & Function found that bananas may reduce the bioavailability of flavon-3-ols in smoothies.
The study was indeed conducted, and several TikTok videos that immediately surfaced online to discuss it more or less accurately described the study’s findings. The mistake was in concluding that we shouldn’t add bananas to smoothies. The scientists came to a different conclusion. There’s no need to give up bananas.
It was likely the press release announcing the study’s findings that started all this confusion (it called adding bananas to smoothies a “mistake”), but it also mentioned that the study’s lead author, Javier Ottaviani, “said bananas remain a wonderful fruit to eat or add to smoothies.” So, it’s clear that the warnings about bananas are greatly exaggerated.
What did the study actually show?
The study didn’t examine the nutritional value of bananas or smoothies in general. It focused on a specific biochemical question: does an enzyme in bananas interact with one specific type of antioxidant found in cocoa extract? (It should be noted that Rhonda Patrick’s recent videos focused on polyphenols in blueberries; these were not examined in this study.)
Antioxidants are a broad class of chemicals. For comparison, vitamin C is an antioxidant, but so are lycopene and resveratrol (compounds known to be found in tomatoes and grapes), as well as anthocyanins—the red and blue pigments found in berries. The antioxidant studied here is not one of these, but a different antioxidant found in tea and cocoa. It is called (-)-epicatechin and belongs to a family of antioxidants called flavon-3-ols.
In the study, eight healthy men recruited from the University of California, Davis, campus area were given each of the following substances on different days:
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A smoothie made with bananas, almond milk and cocoa extract containing epicatechin.
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A smoothie made with the same cacao extract, but with the addition of strawberries, blueberries, blackberries, raspberries, almond milk, water, crushed ice, and yogurt (presumably the yogurt and ice were for texture).
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A glass of milk and a capsule containing cocoa extract.
Bananas contain an enzyme called polyphenol oxidase (PPO), and scientists wanted to see if the PPO in bananas could influence the levels of (-)-epicatechin, one of the flavon-3-ols, in foods like smoothies.
Surprisingly, it worked! Our bodies convert epicatechins into other chemicals in the same family, and the researchers took blood samples from volunteers to analyze these substances after each experiment. After drinking the berry smoothie or taking the milk capsule, blood levels of these substances increased. But after drinking the banana smoothie, this did not happen.
This strongly suggests that polyphenol oxidase (PPO) in the banana destroyed a significant portion of the epicatechins present in the cocoa extract. Further experiments described in the same article show that similar chemical activity occurs when the ingredients are combined in a smoothie glass, and it likely also occurs in our stomachs.
More importantly, the study didn’t find what it didn’t find.
The study did not test a berry smoothie with added banana. None of the smoothies or experiments combined berries and bananas. The study did not measure antioxidant levels or other nutrients in the berries. The researchers specifically examined what happens to the antioxidants contained in cocoa extract. The study also did not examine any nutritional aspects beyond this very specific chemical reaction (polyphenol oxidase from bananas plus (-)-epicatechins from cocoa extract).
Therefore, we cannot conclude that adding banana to a fruit smoothie “destroys” or “spoils” the nutrients or even the antioxidants in the berries. This study focused on a specific type of polyphenol found in tea and cocoa, and it was studied specifically in cocoa extract. We cannot use this data to determine what happens to the antioxidants in the berries.
Why, in fact, nutrients cannot be “destroyed”.
If an enzyme in bananas can reduce the bioavailability of a certain family of antioxidants… what does that matter? Were you drinking a smoothie specifically to increase your flavon-3-ol intake? Chances are, you were trying to add fruit to your diet and/or have a good breakfast or snack because you were hungry.
Despite their PPO (phosphate-propanediol) activity, bananas also contain fiber, which is beneficial for health, and carbohydrates, which are a macronutrient our bodies can utilize in a variety of ways. The average banana contains 20% of the daily requirement for vitamin B6, 17% of vitamin C, and 8% of magnesium. After debunking the banana myth, Patrick made a video in which she points out that bananas also have more sugar than avocados (her favorite ingredient). In my opinion, this is a plus: smoothies need sweetness, and carbohydrates are healthy anyway .
The recent study doesn’t diminish your benefits in any way. You still get all the benefits listed above, regardless of what happens to the flavon-3-ols in your smoothie.
If you’re really concerned about the flavone-3-ol content, there’s a better solution than giving up bananas.
Okay, but what if you’re really hoping to get plenty of beneficial antioxidants in that fruit smoothie? After all, flavon-3-ols like (-)-epicatechin are so beneficial that the Academy of Nutrition and Dietetics (AND) has issued a dietary recommendation for them, despite the fact that flavon-3-ols aren’t essential nutrients . The recommendation states that consuming at least 400 milligrams of flavon-3-ols daily provides health benefits.
If you want to get more flavon-3-ols, tea is your best bet. You can reach the recommended intake of 400 milligrams by drinking just 10 ounces of green tea (two small cups) or 12 ounces of black tea. Flavon-3-ols are also found in berries, but in smaller quantities; to get the same amount as two cups of green tea, you’d need 6 cups of blackberries or 40 cups of blueberries.
Incidentally, the same article that recommended taking 400 milligrams of flavon-3-ols also states that it’s best to avoid getting this nutrient from supplements. This is because the most common supplements containing it are green tea extracts, and large amounts of green tea extracts can cause stomach upset and even be toxic to the liver.