Why Everyone's Arguing About Blueberry and Banana Smoothies

This week, a huge debate sparked after someone suggested that adding bananas to blueberry smoothies could reduce some of the health benefits of the berries. The internet quickly responded, with many accusing her of spreading misinformation and unnecessary fear.

So... who's right?

In this episode, we break down the actual research behind the controversy. We explain what the famous banana smoothie study found, what it didn't find, and why the conversation online became so polarized.
We discuss:

- The human study that started the controversy
- What polyphenol oxidase (PPO) actually does
- Whether bananas really "destroy" the nutrients in blueberries
- The difference between changes in nutrient absorption and meaningful health outcomes
- How social media can exaggerate scientific findings
- What this debate teaches us about interpreting nutrition research

As always, our goal isn't to defend or attack anyone—it's to look at the evidence, discuss its strengths and limitations, and help you understand what the science actually says.

If you enjoy evidence-based nutrition, exercise science, and myth-busting, don't forget to subscribe and let us know what topic you'd like us to tackle next.

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If you are interested in fat loss science, you can purchase Ben's best-selling comprehensive fat loss book, Everything Fat Loss. http://geni.us/EverythingFatLoss

Transcript

SPEAKER_02 0:00

There has been some recent controversy about smoothies. You heard that right. Smoothie controversy. Or hashtag SmoothieGate.

SPEAKER_00 0:10

I never thought we would be making an entire episode based off a smoothie controversy.

SPEAKER_02 0:16

No, but I quite like it. I quite like it as a change of pace. So we thought this would be a nice episode because there has been a lot of controversy that we will explain, obviously. We thought it'd be nice to maybe do a kind of debunking episode. We make videos like this on social media, but why don't we do a mini podcast episode to actually explain to people why everyone on social media is arguing?

SPEAKER_00 0:38

On a viral video. Basically, what's happened is there's a very popular science creator who is on We're not saying names.

SPEAKER_02 0:48

But you can We don't we don't want it to look like we're being negative. We're talking about the information, not the person. Maybe.

SPEAKER_00 0:54

Who this person was on a very popular podcasters platform basically talking about why they no longer add bananas to their smoothies for health purposes. And that video got many, many, many shares and many, many, many people replying to it, basically critiquing the video. Yeah.

SPEAKER_02 1:19

Yeah, so someone uh at least one person, I can't remember how many, I don't tend to count the tags anymore, but people will often send me videos or tag me in videos and say, hey, BDC Carpenter, what do you think? Could you respond to this? Whatever. But by the time I had seen it, so many people had already replied. I don't like it looking like a pylon. If I have seen multiple people responding to the same video, I tend to not want to respond to the same video. But also, sometimes when lots and lots of people respond to the same video, I personally feel like sometimes really good information kind of gets missed out because it becomes a case of who can be the angriest, because that's going to be great for clicks. Right. Now, I think it's important to clarify that this video or this podcast episode is not actually really about smoothies. Yeah. Because that would be a fairly niche, boring episode or mini episode for you.

SPEAKER_00 2:15

But we're not sharing our favorite smoothie recipes.

SPEAKER_02 2:18

We'll do that now.

SPEAKER_00 2:18

Well, I need to delete all my notes. I am not prepared for this.

SPEAKER_02 2:23

We we are this is not going to be about smoothies. Instead, it's going to be a lesson in science literacy. Yeah. So we are going to talk to you about what the research shows and why smoothies are the vehicle. Yeah. But there is a a bigger, a bigger message. Right.

SPEAKER_00 2:37

And and and honestly, despite having this particular video already being covered by many other creators, I thought it was still worth our covering it because I think we have some other points to bring up that we have not seen other creators.

SPEAKER_02 2:53

Yeah, because I I think when you do reaction videos, and I'm I'm obviously not against reaction videos, I make a lot of them, but a lot of the time I personally get the vibe that the angrier people can be in a 60-second or 90-second response, I think the more clicks it gets. But sometimes there's actually some really useful information that then gets missed out. So for example, I have seen people make basically making it sound like the science that this creator was using was bullshit. And that's not actually true at all. But the easiest way to rile up an audience is be like, this is bullshit, this is nonsense, blah, blah, blah.

SPEAKER_00 3:26

And of course the reality is quite a bit more nuanced than that.

SPEAKER_02 3:29

Yes.

SPEAKER_00 3:29

Which is what we're known for.

SPEAKER_02 3:31

Yeah, that's why all our episodes are three days ago.

SPEAKER_00 3:33

Yeah, let's dive in.

SPEAKER_02 3:34

But not this one. This one is going to be shorter. If it's not, we've fucked up.

SPEAKER_00 3:38

Well, we've said that many times before. So let's see how it goes. Let's go over what the actual claim was. What was this person claiming?

SPEAKER_02 3:45

So I have my iPad in front of me because we're actually going to go over the video and explain it for any of you who didn't see it. So her claim essentially was that blending a banana with a blueberry smoothie may reduce how many polyphenols, we'll get to it, you actually absorb from the berries. And instead of using a banana, you would use an avocado. Which on the surface is not a particularly controversial thing.

SPEAKER_00 4:12

Yeah. And I think for someone who isn't super familiar with nutrition science, might say, oh, that's that seems like really great advice. I feel like I can improve my health by implementing this simple swap.

SPEAKER_02 4:24

Basically, yeah, like don't use a banana, use an avocado instead.

SPEAKER_00 4:27

Yeah.

SPEAKER_02 4:27

Meh. Like that's not particularly exciting, but that is not why people got pissed off.

SPEAKER_00 4:32

Yeah. All right. Now to give you the proper context, what we're gonna do is we're going to reenact the lines from the video to help you understand what's going on.

SPEAKER_02 4:41

Yeah, so for anyone who hasn't seen it, when I reenact, we're not actually going to act. We will just read the cliff, the cliff notes of what they said. Just so you know w where we're at. Yeah. So I am the science person. Science person.

SPEAKER_00 4:57

I'm the podcaster.

SPEAKER_02 4:58

Yeah, popular science person, popular podcast.

SPEAKER_00 5:00

Basically, I'm interviewing you.

SPEAKER_02 5:01

Yeah. Yeah. So there is something in a banana called polyphenol oxidase. That doesn't sound good. Doesn't sound good. Polyphenols are the things I said were beneficial. Polyphenol oxidase is an enzyme. By the way, the reason it didn't sound good is because it was a scary word. Like that red flag. Red flag. Yeah. Anyway, polyphenol oxidase is an enzyme which breaks down polyphenols. There are now studies showing that if you add bananas to blueberries, you aren't getting as many polyphenols. In fact, it is quite a bit lower.

SPEAKER_00 5:34

So the banana is killing the benefit of the See, this is why I need you.

SPEAKER_02 5:39

You are actually reenacting. I like it.

SPEAKER_00 5:41

Because I'm sitting here making smoothies smoothies thinking, I like the texture of the banana. It gives it a little heft and creams it out a little bit. But then I'm putting in in my blue blueberries, and then I blew it because the banana cancelled out the blueberries.

SPEAKER_02 5:56

Yes. So End scene. Yeah. So the bit that we would like you to out of all of that, the bits that we would like you to kind of firmly cement in your mind are that banana cancels out the blueberries.

SPEAKER_00 6:10

Is the wording that they use.

SPEAKER_02 6:12

Also the fact that polyphenol oxidae sounds scary.

SPEAKER_00 6:15

Yep.

SPEAKER_02 6:15

That's a bad thing.

SPEAKER_00 6:16

And uh And then and then they also said the banana is killing the benefit. She didn't finish her sentence, but the banana is killing the benefit of the blueberries.

SPEAKER_02 6:25

Yeah. So this isn't just a case of we're reducing the polyphenols. This is like a banana is wiping out the blueberries. Right. And this is why people got pissed off.

SPEAKER_00 6:34

Right.

SPEAKER_02 6:34

So quickly, just so you know what they are, polyphenols are an umbrella term, kind of like vitamins and minerals. So think of them as compounds within food. And polyphenols are an umbrella term for many different subclasses. So you can have, we'll put an image on the screen, but you can have flavonoids and then you can have non-flavonoids. And in the flavonoid family, you can have flavones and flavonoles and uh isoflavones and flavonols, etc. etc. etc. So just because something is a polyphenol doesn't mean that it is very closely related to another polyphenol. They can be in completely different classes of polyphenol.

SPEAKER_00 7:16

Yeah. Then we have polyphenol oxidase, which was mentioned in the video. And that is an enzyme that breaks down polyphenols, like the fruits and vegetables that go brown, similar to when apples, when you cut when you slice an apple, eventually it will turn brown, similar to a banana, obviously. And then the the creator said, Oh, bananas contain polyphenol oxidase. This breaks down the beneficial polyphenols, therefore you should not mix them with blueberries.

SPEAKER_02 7:45

Yes, and polyphenols like vitamins and minerals tend to be viewed as good things. They are linked with better health outcomes. So if you degrade a polyphenol in a certain fruit, that is not a great thing. You want the same way that you want more vitamins and minerals. If you heard that something kills the vitamins and minerals in a fruit, you might go, okay, we don't want that. That is the cliff note. Right. So let's go over the study itself quickly, just so you can understand what happened. Because if you understand what the study did, you can kind of understand why people were giving this person so much backlash. So the study itself actually had multiple parts, but the first part started with eight men, and they had two different smoothies. So the first one was frozen bananas mixed with almond milk, and then the other one was a mixed berry smoothie mixed with almond milk. So remember, two separate smoothies: bananas in one, berries in the other.

SPEAKER_00 8:46

Yeah. To standardize for epicatechin content.

SPEAKER_02 8:50

Which is a type of polyphenol.

SPEAKER_00 8:52

Yeah. What they did was they added a standardized cocoa extract to each smoothie. Okay. Then they had a separate control condition, which included the same epicatechin containing cocoa extract in a capsule form, which was consumed with milk.

SPEAKER_02 9:08

So the polyphenol that we're looking at, epicatechin, is in the cocoa. We are not looking at polyphenols within the blueberries, just so you know. And then to make sure that it was standardized, they would make the smoothies and the participants had to drink it within one hour.

SPEAKER_00 9:22

Yeah.

SPEAKER_02 9:23

Now that's actually worth remembering as well. We'll come back to this.

SPEAKER_00 9:26

We're gonna come back to this. And what they were measuring, the outcome variable was the bioavailability of flavanols.

SPEAKER_02 9:32

Now, just to reiterate and drive this home, at no point was this testing whether blueberries were mixed with bananas. Yeah. It wasn't like we have a banana smoothie and we have a banana and blueberry smoothie, and the banana fucked that smoothie up. It is more like we have a banana smoothie and we have a blueberry smoothie or a mixed berry smoothie, and we are seeing what happens to the content within cocoa, not the polyphenol content within the berries themselves. Right. That makes sense. I've reiterated that enough. People are on board, do you think?

SPEAKER_00 10:10

Yeah.

SPEAKER_02 10:11

Great.

SPEAKER_00 10:11

Therefore, a more accurate representation of the study findings would be to say that okay, banana mixed with cocoa degrades one of the polyphenols within cocoa, not blueberries.

SPEAKER_02 10:22

Yes, and the polyphenols most prevalent in blueberries are not the same as the ones most prevalent in cocoa. So in blueberries, the most prevalent polyphenol content is something called anthocyanins or anthocyanidins, which are responsible for giving blueberries their colour. So in the same way that blueberries are blue, purpley colour, but berries have a kind of red or blue or purple purple colour to them, the polyphenols responsible for that are not the same as the polyphenols that are high in cocoa. So if one degrades within cocoa, it doesn't necessarily mean that it degrades within berries because they're not the same. Right. They are from completely different subclasses of polyphenol. Yeah. It'd be a bit like saying this vegetable has vitamin C degraded, but you compare it to another vegetable which is high in vitamin E, not vitamin C.

SPEAKER_00 11:17

Yeah. Now, the next interesting point, which we thought was very curious that the authors of the paper didn't explicitly address this in the study findings, but we actually found it in the supplementary graphs was that the duration of how long the smoothie was left out for before it was consumed made a big difference in terms of the the polyphenol bioavailability. So if you drink a smoothie within 10 minutes of making it versus waiting up to an hour, that made a big impact.

SPEAKER_02 11:49

So think of it like this: if you have an apple and you cut it open and you leave it for a day, it will be significantly browner than if you cut it open and leave it for a few minutes. So that clearly shows that something happens that can degrade the fruit and the polyphenols within that fruit. And in this instance, yes, if the smoothie sat there for longer, that would have a bigger impact. So if you had a smoothie and you drank it fresher, the impact would tend to be smaller. Yeah. And significantly smaller as well.

SPEAKER_00 12:18

Yeah. And I think it'd be safe to say the vast majority of us do tend to drink our smoothies pretty much right away.

SPEAKER_02 12:24

Yeah.

SPEAKER_00 12:25

Therefore, is this the are the findings really?

SPEAKER_02 12:28

Well, it depends. If you're making a smoothie at home, you're probably going to drink it fresh. If you're buying one or having it in a bottle, like I think that's different.

SPEAKER_00 12:37

Yeah. The other thing that's important to drive home is that this study, while legitimate, is a small mechanistic study. And if it does not what they they showed, okay, this affected the bioavailability, but it did not show it translated, therefore, into meaningful outcomes in health. It negatively impacted your health in such and such way. That's not what they showed.

SPEAKER_02 13:01

Yeah. So this was the first part of the study. There was another part of the study where they actually had two different drinks and they would alternate sips. We don't need to go into that. We just need you to kind of be aware of how they did things. But essentially, what this study shows is that yes, bananas can degrade polyphenol content within cocoa. Therefore, it is possible that fruits and vegetables with a higher polyphenol oxidase content could degrade polyphenols in other foods. That's fine. The science is fine. There's nothing wrong with the study itself. That's not what people are criticizing it for. It's more about does this actually make a difference in the real world to anything? Yeah. So if we have a this this study that looks at um the bioavailability of polyphenols, that is important. But does it actually impact someone's health in the long term if they have a smoothie with a banana on occasion versus a not banana?

SPEAKER_00 13:55

Like Right. Yeah. Now, if your particular goal is, hey, my goal in life is to maximize polyphenol bioavailability in all the foods that I eat, then sure, maybe the findings of this study are meaningful for you. But if not, not sure if it's something you need to worry about. Not sure that the study, this study on its own is not enough to justify creating a whole new food rule, which according to going back to the original social media video in question, is allegedly don't blend bananas with your blueberries.

SPEAKER_02 14:30

And it's killing the benefits of the banana.

SPEAKER_00 14:32

Yeah, it cancels out the blueberries.

SPEAKER_02 14:34

And this is the more important part of this episode. So it isn't necessarily about the smoothie itself. We don't care about talk to talk about smoothies that much. The whole point is that this is one of those things where it's majoring in the miners. We are talking about polyphenol content within smoothies. How many people are drinking smoothies to begin with? How many people are consuming enough fruits and vegetables to begin with? We are zooming in on a problem which isn't a problem for the vast majority of people.

SPEAKER_00 15:02

Yeah. Now, we have, according to the CDC, roughly 10% of adults are not consuming enough fruits and veggies on any given day as it is. When we create a new food rule like this, it could be the case that the only way someone is getting in bananas is in the form of a smoothie. And if we say, okay, now don't do that, all of a sudden they're getting rid of the banana, for what? What's the net benefit here?

SPEAKER_02 15:28

I actually that that brings a point. I don't know if we this was something that we would talk about later, but before I forget, if you are reducing a polyphenol within a fruit or a vegetable, that doesn't mean it's across the board. Like if you are consuming a banana, for example, bananas have their own vitamins, minerals, fiber, etc. So introducing something with a plethora of benefits, even if it reduces the one specific polyphenol or one specific polyphenol family content, that doesn't mean that the banana is now a negative. Right. Does that make sense? It's like if you had kale and broccoli and you found out that introducing kale means that broccoli slightly reduced one specific compound. It doesn't mean that the kale is now useless and the broccoli is worth less than it was before.

SPEAKER_00 16:15

Right. The banana still has potassium, vitamin B6, vitamin C fiber, the blueberry still has its own nutrients. Both are going to still be meaningful and they're both going to add up if you consume them as a regular part of your diet.

SPEAKER_02 16:30

So to just try and drive home, I personally think how ridiculous this is. The fact that this has become the thing that they're talking about. If you have a popular podcaster and a popular science creator who is a very smart person, the fact that this is the thing they're talking about, I just think it would be funny to give some other examples of things that you can blow out of proportion. Yeah. So for example, if you microwave garlic or if you heat garlic, you can reduce the anti-cancer properties of garlic.

SPEAKER_00 17:03

Yeah. Also, if you cook broccoli, what's going to happen is you significantly reduce the bioavailability of the anti-cancer compound, sulforophane, compared to eating it raw. Therefore, it's easy, it might be easy to say you can never cook or roast your broccoli, even if that's how you prefer it.

SPEAKER_02 17:20

Boiling vegetables can significantly reduce vitamin C content, anything from 26% up to 100%.

SPEAKER_00 17:28

And shredding sweet potatoes significantly increases polyphenol oxidase activity, similar to the claim that this original creator was making, and decreases antioxidants.

SPEAKER_02 17:39

That was actually quite funny when I found that because they tested different ways of cutting a potato to then test the enzymatic activity. So in the same way that if you say you peel an apple or if you cut an apple or if you cut it into multiple parts, it's like the more you chop it, the more it can degrade because I assume more oxygen is getting to it.

SPEAKER_00 17:59

It makes me wonder how do they how did researchers even come up with the study design and the debate.

SPEAKER_02 18:03

I don't know, but imagine we made a video where we're like, from now on, you can never cut potato into small pieces.

SPEAKER_00 18:09

You could only cut them into half-inch widths.

SPEAKER_02 18:13

Ideally, you need to cook a potato whole. The moment you cut it, you are significantly, significantly reducing the quality of that potato. Never ever slice a potato, shred a potato, whatever.

SPEAKER_00 18:27

Yeah. So this brings me to the analogy I love, which is comparing big rocks to petals or maybe pieces of sand or grains of sand. If you have a big jar, the jar represents your health. The big rocks are obviously going to represent the things that make the biggest impact. The the the actual dial movers, things like consistent fruit and vegetable intake, regular exercise, sleep, stress management, social support, things like that. Those are going to be the big rocks. Obsessing over should I mix bananas with blueberries? That would be the tiniest, tiniest grain of sand you could possibly find, and you drop that into this big jar. What difference is it actually going to make? Versus, okay, even if I'm mixing blueberries with bananas, that's still going to increase my total fruit consumption for the day. That is a major win, and that is the part that you should be focusing on.

SPEAKER_02 19:25

The unfortunate thing that you need to understand is that good quality health advice is boring, and boring does not do well on social media. So the most well-established health-promoting behaviors are things like exercising regularly, consuming enough fruits and vegetables, consuming enough fiber, not consuming too much added sugar. All of those things work great, but they're boring. And this is one of the reasons why social media content creators go to either side of what I call the bullshit information spectrum, which is you can make something sound super exciting, or you can make it sound super scary. And that is part of the reason why you see so many videos on social media of people saying, This food is going to kill you, or adding this fruit to your smoothie is going to destroy the polyphenol content, and therefore it's cancelling out all of the goodness in the other fruit. And that is what social media algorithms will reward. So it is very important for you to understand that there are a lot of really incredibly knowledgeable creators putting out really good quality health advice who are overlooked and overshadowed by people who know how to play the social media algorithm game by essentially making up or exaggerating clickbait bullshit.

SPEAKER_00 20:52

That actually reminds me of our grocery store satire video we did a few years ago.

SPEAKER_02 20:56

Yeah, that was.

SPEAKER_00 20:57

Where basically we were, as you would say, we were taking the piss out of all the creators who go to the grocery stores, pick up a food and say, This food is killing you. And we use all the buzzwords toxins, poisonous, this and that. And uh that video did really well. It got it got a lot of traction.

SPEAKER_01 21:13

We should do that. We should do that again.

SPEAKER_00 21:15

I honestly I think we should.

SPEAKER_01 21:16

We should do that again.

SPEAKER_00 21:17

But my my hesitation with that, my the hardest part of that is first of all, I want to know how do these people create so many grocery store videos? Because the amount of embarrassment I felt being there, I hated it. I was like, I don't want the manager to walk by the aisle while we're we have our cameras out here.

SPEAKER_02 21:33

Recording in in a grocery store was probably my least favorite video I've ever made. We we actually went late at night on purpose.

SPEAKER_00 21:39

Yeah, it was like 10 p.m. or something when it was quieter, so we wouldn't have people watching us.

SPEAKER_02 21:44

Yeah. Um at least you know what?

SPEAKER_00 21:46

At least we didn't um well, I say we. We weren't shirtless. We weren't doing shirtless grocery store videos. That would be properly insufferable.

SPEAKER_02 21:53

Yeah, would be especially controversial if you did it.

SPEAKER_00 21:56

Yeah. Okay, to summarize, this episode is not about our bananas good for us, our bananas bad for us. It's about what that original message represents, which is that viral, scary health claims. They attract attention, but do they actually have merit to them? And I want us to be able to interpret these message messages with a more critical eye, instead of saying, well, this person has a big following and they have a PhD and they're speaking with confidence, three dangerous combinations, therefore what they're saying must be legit. This is a lot of the appeal to authority, for example, by the way. Let's actually think about okay, what is the study that they're referencing? What's the sample side? Is this a mechanistic study, or is it actually uh delivering the outcomes that this person is claiming? And with all of this combined, do I have to actually worry about this?

SPEAKER_02 22:50

Yeah, so if you can degrade the quantities of certain nutrients in a potato based on how you cut it or broccoli on how you heat it, whatever, whatever, it's interesting to know. Like the science is fine. That's not a problem. There is not a problem with the scientific study itself. Right. It's how it's then misrepresented and exaggerated across social media. Because if slicing a potato means that you can degrade it faster than leaving it whole, for example, you wouldn't leave an apple in the fridge sliced up for a week and expect it to be as good as an apple that you didn't slice up. But if you consume a smoothie with a banana or not a banana, over the course of five years, would there actually be a meaningful difference on your health? Because that is not the only source of polyphenols that are consumed. You are still adding a banana versus not adding a banana. So this is an example, I think, of zooming in on a minuscule problem that is also only relevant for a minuscule portion of the population and blowing it out of proportion, misrepresenting what the research said, and also not correcting the interviewer when she said, So this cancels out the other fruit. That's literally that's not even what the study showed. That isn't what the study was even looking at. They were looking at polyphenols within chocolate, which was not part of the conversation. So this whole a banana cancels out the berries is that's just literally not what it showed.

SPEAKER_00 24:16

Yeah. Be wary of sensationalist language like that, and hopefully we can all learn to be more skeptical of these kinds of viral claims. There is some flavanol for thought for you. Was that really good?

SPEAKER_02 24:29

I yeah, I think Flavanol for thought. Yeah, some food for thought. Fla I say flavanol for thought. Either or. Either or is fine.

SPEAKER_00 24:39

I'm pretty happy with that.

SPEAKER_02 24:40

Some yeah. Yeah, okay.

SPEAKER_00 24:41

Catch you next time. I hope you've enjoyed it.

SPEAKER_02 24:43

If you have enjoyed this shorter episode, please let us know. And also, if you have enjoyed it, please feel free to request other topics.

SPEAKER_00 24:50

Also, definitely send us more of these kinds of that is literally what I said.

SPEAKER_02 24:54

Please request more topics. Yeah, okay, yeah. Same thing.

SPEAKER_00 24:57

I meant like send us the actual video. Yeah. Okay. Yeah, good. Okay, ditto. Okay.

SPEAKER_02 25:03

Love you, bye.