Aliquot #110: Why I don’t mix bananas and polyphenols — and other smoothie tips

Foods are complex. They contain a vast array of nutrients, fiber, and bioactive compounds packaged up into a complex physical chemical structure called the food matrix. The various components of the matrix often work synergistically to promote health, but sometimes the compounds can work against each other, limiting their absorption and diminishing their healthful effects. In this Alloquat, I answer your questions about the possible conflicts between matrix components in bananas and dairy products that might diminish the healthful effects of polyphenols. Let's start with bananas. Bananas are rich in potassium, magnesium, vitamin B6, and other important nutrients. Their natural sweetness and texture make them perfect for adding to oatmeal, smoothies, and other healthful foods.

But bananas also contain an enzyme called polyphenol oxidase, or PPO for short. PPO is involved in the natural browning of fruits and vegetables that occur as they ripen. PPO can degrade polyphenols, canceling out some of the beneficial effects of what might be an otherwise healthful food. Listen as I explain from Q&A number 52. The first question, and there was sort of a related question from Stephanie and Steve about, first of all, my smoothie. So Stephanie says, on the call last month, you suggested we remind you to cover your smoothies. You said you had an update for everyone. Will you please address your smoothies? And then The related question from Steve was about bananas destroying polyphenols.

Steve asked if I had seen the study, and indeed I did see the study, and this was the the reason for updating my smoothie ingredients. So let's just talk a little bit about that for those of you that are unaware of this this recent study. So it came to my attention that basically adding a banana to your smoothie could negate and degrade polyphenols. And those are obviously beneficial compounds. We've talked a lot about them. If we're talking about in the context of a smoothie, usually they're found in the berry, the berries like blueberries, for example, are high in polyphenols. So there's an enzyme inside that is in some foods and very high in bananas. The enzyme is PPO, and it basically chews up and degrades polyphenols.

What the, this particular study did show was that if you drink a smoothie that's high in, for example, epicatechin. So epicatechin is a type of polyphenol. It is found, um, very concentrated in green tea. I've got my matcha, my Jade Matcha Green Tea here, and cocoa. Um, but it's also in, in blueberries as well. The PPO enzyme degrades epicatechin. and therefore reduces the amount of epicatechin that's found in plasma in people. And we're talking, when I say reduces, I mean more than 80% reduction. We're talking just, you know, astronomical. So in a subsequent study, people were given polyphenols and they were co-ingested with a very high PPO banana drink.

In this context, the metabolites of the epicatechins or the polyphenols were were reduced, basically suggesting that eating— and we're going to talk about what foods are high in PPO— eating foods that are high in PPO or blending them together, even eating them like a banana and blueberries or a banana mixed with blueberries. Like, I went and got, you know, an acai bowl the other day for my son, and there was like banana and blueberries and acai. And I'm like, oh, the banana, you know, is kind of negating all this. So we took the banana out. What the study does not tell us is how high the PPO activity needs to be to have a significant effect on epicatechin or polyphenol levels.

So we can only say that the activity of about 96 international units per milliliter, which is included in a drink that has about 50 grams of berries, so including blueberries and blackberries, raspberries, strawberries, these all have the polyphenols, that does not have a significant effect. So, so 96 international units doesn't do really anything to the polyphenols. But when you go really high to almost 9,000 international units, so this is a drink that now contains about 177 grams of banana, then you're having a really significant effect on lowering the polyphenol levels. It's difficult to extrapolate the results to other foods because they really only tested the PPO activity per mL of the drink and not per gram of the ingredients.

I, you know, those, those, those polyphenols that were tested also were only the epicatechins. So there was not other types of polyphenols as well, because there are, of course, a variety of different types of polyphenols. I would say, in my opinion, and this is where I'm going to talk about a little bit where I've made a change in my smoothie ingredients, I think it's just best to avoid Eating, mixing foods that are high. The really the the biggest food that's high in PPO is banana, but we'll talk about another one in a second. So I would avoid mixing those foods together in the smoothie and just eating them right back to back if you're if you're going to eat something with polyphenols. So that includes cocoa via. It includes matcha green tea.

It includes all those types of blueberries, blackberries. You know all that stuff that has the polyphenols. Because it can degrade them. And I think that it's, there's a good chance that it might affect your polyphenol levels, which is essentially what you don't want. So some foods that are high in PPO, uh, I have a chart here. So banana is really the highest. So if you look at the activity of the PPO, it's about 3,258 units per 100 grams. Now, the other one that's really high are beet greens. So these are the greens that are like, come outta beets. Those are close to 1,600 units per 100 grams. I would say that what piqued my interest on the beet greens was I, I, oh, there's like the stem and the leafy green, and it kind of looks a little bit like chard.

And so I started looking up Swiss chard because I often will add as a Swiss chard is a great source of vitamin K1. It's a great source of lutein, zeaxanthin. Of, you know, magnesium, calcium. There's a lot of micronutrients. It's a very, very healthy leafy green to eat. And so, um, I would often add it to my smoothie if I had it around in the refrigerator. And apparently the Swiss chard is much, much like the beet greens with respect to the PPO. In fact, the first time that enzyme was ever isolated, it was isolated from Swiss chard. So that's the biggest change I've made to my smoothie is the Swiss chard. Apples, particularly Red Delicious, have about 570, significant drop from like a banana. But I would say after that, everything else kind of really drops down to almost nothing.

So like I was concerned about avocados because I add avocados to my smoothie, but avocados have a very, very low amount of PPO, like 24 units per 100 grams, comparing the same units that we've been talking about. So I would say bananas are the biggest thing. Swiss chard is also the big, another big one for me that I'm no longer putting in my smoothie. Interesting tidbit of information, vitamin C is an inhibitor of PPO. So obviously the berries themselves have vitamin C. Adding extra vitamin C in there could also help to maintain polyphenol content in smoothies. So that's another interesting piece of information as well. But nonetheless, I do think this is extremely important, especially like a lot of kids' smoothies have bananas in them. So I think that it's good information.

I'm certainly not putting bananas in, in my son's smoothie either. Some people in the chats were talking about studies being poorly done. I don't know that it's necessarily poorly done. It was a small study. There was a lot of things that weren't tested, like I mentioned, right? I mean, um, but I think at the end of the day, the, the, the bottom line is that PPO is very high in bananas. And so a lot of people are adding bananas to their blueberry smoothie, essentially. And the other take-home really is like, if you're drinking your CocoaVia, so I typically drink my CocoaVia in the afternoon when I need a little more pick-me-up. I add a small amount to my coffee as well in the morning, but make sure that you're not eating a banana and washing down the banana with some CocoaVia, right?

Because then you're going to be degrading a good portion of those epicatechins that are Doing so many beneficial things in the CocoaVia. It's not just the smoothie, but just having the greater context, like having that information in your head. Oh, if I'm gonna have a banana, I shouldn't be eating it with my cocoa or my green tea or my blueberries or something with polyphenols. So I think those are the most important things. And then of course I mentioned the chard. If I'm gonna put chard in a smoothie, it's gonna be a smoothie that is greens. It's gonna be one of those chug it down for the greens. The other thing I like to do with chard is I like to just do a little bit of like blanching of it and eating them like a little bit, just a little bit blanched.

And I think that's also a really good source. There's no other greens that I would be concerned about. There's no other greens that have any high PPO activity. It's just really the beet greens and the Swiss chard. So spinach, kale, romaine lettuce, all those types of greens are, are, Totally, you know, fine. And they have a low PPO content. I think the biggest thing people have to worry about is bananas. A lot of people, I mean, think about any smoothie place you go to, the main staple ingredient in every smoothie is a banana. I think that's the biggest take-home here is that bananas are really— most people are not putting Swiss chard in their smoothie. I mean, we do it, right?

Like, that's like, we're trying to get a lot of the greens, but it's really the banana that I think has a broad application here. It wasn't a comprehensive study, but I do think there's going to be follow-up studies on it. And I think that it's pretty simple to apply this to our life. It's not going to make that much of a difference. It's not like you can't eat bananas. It's just that I wouldn't eat them in combination with polyphenol-rich foods. And that's really the bottom line with that. Let's move on to dairy products like milk, yogurt, and kefir. Dairy products are rich sources of protein and calcium, and in the case of kefir, probiotics.

But research shows that the primary proteins In dairy products, casein and whey bind to nutrients and polyphenols in the gut, influencing their bioavailability. In some cases, the proteins increase bioavailability, and in others, they decrease it. In this segment, I discuss how dairy products influence polyphenol bioavailability in blueberries, cocoa, and tea, and present some tips for offsetting this problem from Q&A number 56. All right, so I'm going to move on to one of the deeper dive questions, which I personally was very interested in. I know I'd talked about it in a previous So, Frank submitted a question about how to take polyphenols. And Frank says, recent research has shown that dairy in coffee reduces the bioavailability of polyphenols in coffee.

What does that mean for CoQovia, blueberries, strawberries, smoothies? You guys get the point. Adding things like kefir or yogurt to them. I did talk about this in Q&A number 38, but I'm going to go ahead and go into a little more detail today. So, just for a quick background. We're talking dairy milk proteins. They're divided into 2 classes. So there's the caseins, and then there's the whey proteins. So the whey proteins in milk mainly consist of beta-lactoglobulin, alpha-lactoalbumin, and immunoglobulins. And then there's bovine serum albumin, or BSA, and these are globular proteins. Let's talk about those proteins and polyphenol binding. So caseins, which make up a big part of milk protein, are also rich in a variety— they're an amino acid called proline.

And so this makes them super effective at bonding with polyphenolic substances through 2 main types of interactions, one that's a bit like oil, the other one's a bit like water. So it's like hydrophobic interactions like fats and then sort of like magnetic attractions like hydrogen bonding. So they really have 2 ways, these proline residues, interact with the polyphenols. So whey proteins, they contain the beta lactoglobulin, and that is a key whey protein that's able to bind important nutrients like vitamin D, retinol, tea polyphenols, DHA from omega-3, resveratrol found in, you know, the skin of grapes.

And then there's another whey protein, alpha-lactoalbumin, which is a little bit more selective, and it forms stronger bonds with retinol, vitamin D, palmitic acid, which is a type of fatty acid. And then there's BSA, which is another whey protein that interacts with flavonoids. So that's a type of polyphenol like luteolin, apigenin. These are both known for their antioxidant and anti-inflammatory properties. The interaction between proteins like caseins and whey protein in milk and polyphenolic compounds doesn't necessarily mean it's going to negate all the positive effects of the polyphenols. Sometimes these interactions can influence how the polyphenols are absorbed and utilized in the body. It can either increase absorption or decrease absorption.

So for example, when polyphenols bind to proteins, it can affect their bioavailability, which is the amount of compound that is being absorbed, used by the body. So in some cases, This binding could reduce the immediate absorption of the polyphenols, but it doesn't necessarily mean that it's going to negate all the health benefits. But it does mean that there will be, quantity-wise, a reduction, right? Because if you are not absorbing as much of the polyphenols, you're not going to get as much of the health benefit, right? Proteins can also protect polyphenols during digestion, so they could potentially lead to a more controlled release in the intestines where they're absorbed, more So it makes them sort of absorb more effectively, which is what I just mentioned. It can go either way.

And this would actually enhance the bioavailability of the polyphenols in some context. And it really seems like it is all very specific on the type of interaction that's happening. So what type of milk protein are we talking about? Whey, casein, which specific proteins within those? What type of polyphenol are we talking about? So it really— Is a complex metabolic process, and I will just tell you right now, there is not enough literature to make definitive conclusions about every single type of polyphenol because it just hasn't been researched.

But researchers are looking at how antioxidants and polyphenols from foods behave when we consume them, especially the levels, you know, plasma levels of polyphenols, how well they're absorbed, so that would be the bioavailability, I'm looking at things like antioxidant activity as well. There's a lot of structural diversity of polyphenols. So polyphenols are very large groups of compounds. They have very diverse chemical structures. So the diversity means they can interact differently with different proteins found in milk, such as the caseins and the whey proteins. And the structure of each polyphenol really does affect how it's going to interact with that protein. And that will then, you know, affect the absorption and then obviously the antioxidant effectiveness as well.

There also is a role for concentration, right? How concentrated is the polyphenol that you have in there relative to the milk protein, the casein or the whey, for example? So higher or lower amounts, right, will make a difference as well in terms of absorption and function. So let's talk about some data. I will say there are some conflicting studies out there. These different studies might use different techniques, different concentrations of the polyphenols like we just talked about. There's all sorts of levers to pull here that might change the outcome. So let's first talk about blueberries. There's really, really, really limited research with blueberries.

So there was one study that tested how blueberries' antioxidant levels are affected in the body when they're eaten with water versus whole milk. So participants who drank water with blueberries had a really strong improvement in their antioxidant levels, but those who had milk with their blueberries did not. So the study also found that blueberries with water led to better absorption. And they also had higher antioxidant activity as well. So it seems like the milk was binding to the polyphenols and it was limiting the bioavailability and thus antioxidant capacity as well. My take-home with respect to blueberries and smoothies in particular, right, really is that— so I would sometimes add whey protein to my blueberry smoothie if I needed extra protein.

I certainly was doing it in the case of my son where I was trying to get him extra Greens and blueberries and protein altogether. I'm no longer adding whey protein to my smoothie with blueberries or my son's. So I still use whey protein, just I'm using it by itself and not in my blueberry smoothie. Instead, I did order a new type of plant-based protein powder just for the smoothies, particularly for my son because I like to, you know, it's for 6-year-olds, you're always trying to get them more protein. And veggies and smoothies are great ways to do that. So I looked, of course, at ConsumerLab, which is one of my go-to sites that I like to look at for protein powders and powders and things like that.

And my top choice for plant-based protein powder to add to my blueberry smoothie is sprouted quinoa protein. A couple of reasons for that. First, it's a complete protein, so it contains essential amino acids, including leucine, which is the major amino acid involved in muscle protein synthesis. Pea protein is another good option. It also is high in branched-chain amino acids, but it does contain some phytate in it, which can limit mineral absorption. And so, if you're adding this to a smoothie with kale and greens and things where you're trying to absorb magnesium and calcium, there will be a little bit of a limiting of the bioavailability of those minerals if you're adding a bunch of pea protein powder, which has phytate.

The reason I like the sprouting quinoa is because sprouting does decrease phytate levels. Quite a bit. And so I found a pretty good protein powder called Plant Fusion Complete Protein, which I have no affiliation with, but it has a blend of pea protein isolate, a little bit of that, but it also has a blend of sprouted quinoa protein and sprouted amaranth protein, as well as some BCAAs added in. So it's not just 100% pea protein isolate. So the phytate level is reduced because it's got the sprouted quinoa and the sprouted amaranth as well. So that's kind of my new protein powder to add to my son's smoothie, which has blueberries, and also if I'm going to make my smoothie with blueberries and I want a little bit of extra protein as well. Let's move on to the tea.

So research has found mixed findings with respect to adding milk to green tea and black tea. Some studies suggest that milk may diminish the antioxidant effects and the overall health benefits of both green and black tea. However, there's some contrasting research indicating that milk does not significantly alter antioxidant properties of these tea. when measured in the bloodstream. So I think some of this does have to do with directly measuring antioxidant activity in blood versus the levels, because if your endpoint is just measuring antioxidant activity, and let's say the milk is limiting bioavailability, it's not sequestering the actual antioxidant function of the polyphenol, then if you're just measuring that, you're going to see the same effect.

Whereas if you're looking at both the amount and the activity, then you'll see, well, the activity is still there, but you have a lower amount of it because there are fewer polyphenols that have made its way into the bloodstream with the milk bound to it versus the, for example, just in water. So I think obviously there's a lot of complexity going on with this type of scientific research. Again, I said there's lots of little levers you can pull that can sort of affect the results and affect your conclusions, but my take-home is it's better to avoid dairy in tea if you're looking for the polyphenol antioxidant benefits. Anti-inflammatory function in the teas. With respect to cocoa, research on the interaction between milk and chocolate has varied results.

So there's one study that found that chocolate's polyphenols, which are obviously very known for their antioxidant properties, they have very important effects on vascular health, improving blood flow, endothelial function. So there are studies that have found higher antioxidant capacity when the cocoa is consumed without milk or when it's consumed as dark chocolate versus the milk chocolate. In contrast, there's another study that found adding milk to chocolate did not really impact the bioavailability of some of the polyphenols like epicatechins, which is one of the key ones in cocoa.

Again, it's one of those things where there's a lot of variation in the literature, but the fact of the matter is there are quite a few studies showing there is a negative effect on the antioxidant activity and bioavailability of cocoa polyphenols, and I think that it's better to avoid adding dairy to them. And if you really need to add some kind of cream, it's better to do a non-dairy cream like coconut milk or, for example, almond milk. And then the same goes with coffee. I mean, there's not like a ton of evidence, but there's one study that found consumption of coffee with milk was reported to decrease urinary excretion of chologenic acid, which is one of the main bioactive antioxidants found in coffee.

So I think my total summary, my thoughts on this topic, generally speaking, is yes, there's a lot of structural diversity among polyphenols. So their interactions with milk proteins can vary significantly. However, given the data we have, it's still unclear how each and every polyphenol from each and every food type that contains them is interacting with dairy proteins. For that reason, because there is data showing they do interact and there is a limited limitation on bioavailability of some of these polyphenols as well as antioxidant activity. I think it's safe to avoid dairy when consuming these polyphenols. So don't mix milk with coffee or tea or cocoa. Instead, go for a non-dairy alternative like almond milk or coconut milk. And the same goes for blueberries.

Rather than adding yogurt to them, unfortunately, you're better off sticking to the water, or if you need protein powder, sticking to the plant-based just in that one scenario versus the whey protein, because there's so many benefits with blueberries. I mean, it increases brain-derived neurotrophic factor, and this is in human studies, improves cognition in young and old. I mean, across the lifespan, there's just every reason to want to get just equivalent of a cup of blueberries a day. And so you don't want to limit the bioavailability of the polyphenols in those blueberries or— inhibit the function or antioxidant function of those polyphenols or anti-inflammatory function of those polyphenols. So I think it's just better safe than sorry.

Everybody knows it's tough to get kids to eat enough protein and calcium-rich foods. Greek yogurt is a great option for kids because it contains lots of protein and calcium and is a great vehicle for polyphenol-rich berries and other healthy toppings. But should you be worried about mixing dairy products with berries when feeding growing children? Probably not. Listen as I explain from Q&A number 57. Lisa asked about mixing berries with yogurt, how it's very frustrating that proteins in yogurt are inhibiting polyphenols, and the bananas we had to worry about, and it's nice to give our children blueberries with Greek yogurt. Do we have to worry about all this stuff? Is sheep's milk better or goat's milk better? What are my thoughts? I hear you loud and clear.

I personally think that adding Greek yogurt, cow milk, goat, whatever, With the berries for your kids are fine. Honestly, the impact on polyphenol bioavailability and absorption, it could be very minor. And overall, getting the protein and the calcium and all that stuff to the kids, it's really important. So I don't know that I would necessarily freak out about having yogurt and blueberries for the children. Now, for us, trying to get the cognitive benefits, we don't want to probably add dairy to our smoothies and stuff. But there's a lot of concerns of getting enough of protein and other nutrients to kids, and it's— the kids are a lot more picky eating, and so it's a very different set of concerns. Goat and sheep dairy products might be a healthier alternative for some individuals.

Obviously, they're a little bit more digestible for some people, but again, I don't know that you have to. So I'm just not terribly concerned about having Greek yogurt with the blueberries and giving that to your children. I think that's fine. As always, thank you so much for listening and for your support, and I'll talk to you soon.