Bananas in smoothies yay or nay?

If you follow health and nutrition news, you might have heard that you should never put bananas in smoothies. In this article, we will attempt to answer the question: Bananas in smoothies, yay or nay?

A recent study found that pureed bananas (as in smoothies) have increased activity of an enzyme that degrades a type of polyphenols (1).

Among health and nutrition experts, Dr Rhonda Patrick PhD is one of the most credible sources that has brought this research to people’s attention in the past few weeks. Check out the clips below:

• This is why Rhonda Patrick stopped adding bananas to smoothies
• Why Dr. Rhonda Patrick Changed her Mind on Skipping Breakfast, Eating Bananas and More

Below are some examples of media headlines for the same study:

• “New Research Reveals Why You Shouldn’t Add a Banana to Your Smoothies” SciTechDaily.com
• “TikTok Myth of the Week: Bananas Destroy the Nutrients in Smoothies” Lifehacker.com
• “Adding Bananas to Your Berry Smoothie May Make It Less Nutritious, Study Finds” Health.com

The study

The research paper (1) included 2 studies which analysed the effect of the enzyme polyphenol oxidase (PPO) on (−)-epicatechins. (−)-epicatechins are polyphenols that act as antioxidants and belong to the broader category of flavan-3-ols. Flavan-3-ols may reduce3 the risk of cardiovascular disease and diabetes, among other potential health benefits (2).

Participants were healthy male adults between 25 and 60 years of age. 6 subjects completed study 1 (there were capsules and smoothies involved, 8 completed the capsule intervention and 6 completed the smoothie intervention) 11 subjects completed study 2.

Study 1 compared a banana smoothie to a mixed berry smoothie to a (−)-epicatechin capsule + cow milk. All of these were standardised to contain the same amount of s (−)-epicatechin.

Study 2 compared a berry smoothie alone vs a berry smoothie drank alternated with a banana smoothie, so that the banana was not in direct contact with the polyphenols in the beverage, but came in contact in the digestive tract of the participants.

The researchers found that the PPO activity from bananas lowered the amount of (−)-epicatechin in the blood of participants. The effect was more pronounced when the PPO were in direct contact with the (−)-epicatechin (for example, a smoothie containing both bananas and berries) than when those were mixed in the stomach.

Bananas in smoothies, yay or nay?

• The PPO enzyme in bananas increases activity when pureed, which happens when you make a smoothie. This is a very common use of bananas.
• Other foods also display PPO activity (e.g. beetroot leaves, red delicious apples, pears), however bananas seem to be highest in the list (1).
• Flavan-3-ols are only one type of polyphenol and polyphenols are just one type of beneficial phytochemicals. Having said that, the authors of the study indicated that PPO might have similar effects on other polyphenols and other nutrients.
• There are many other nutrients that have effects (both beneficial and detrimental) on health
• Eating a banana and drinking a glass of milk will almost always be a better option than drinking a banana smoothie.
• Drinking a banana smoothie will almost always be a better option than eating ultra-processed food.
• As a general rule, a wider variety of foods in your diet (not only individual foods but also preparation methods) will give you a better chance of reaping the benefits of synergistic effects between food components.
• If you haven’t nailed the fundamentals of a healthy lifestyle, focus on those first, then worry about details such as antioxidant status.
• If you are optimising for antioxidant intake, try not to mix antioxidant-containing foods (e.g. berries) with bananas in your smoothie. Also, increase your antioxidant intake for berries or other sources, preferably a few to several hours away from that banana-containing smoothie.

References

1. Ottaviani JI, Ensunsa JL, Fong RY, Kimball J, Medici V, Kuhnle GGC, et al. Impact of polyphenol oxidase on the bioavailability of flavan-3-ols in fruit smoothies: a controlled{,} single blinded{,} cross-over study. Food Funct [Internet]. 2023;14(18):8217–28. Available from: http://dx.doi.org/10.1039/D3FO01599H
2. Crowe-White KM, Evans LW, Kuhnle GGC, Milenkovic D, Stote K, Wallace T, et al. Flavan-3-ols and Cardiometabolic Health: First Ever Dietary Bioactive Guideline. Adv Nutr [Internet]. 2022;13(6):2070–83. Available from: https://www.sciencedirect.com/science/article/pii/S2161831323000637

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