“Welcome back to the podcast. Today we're going to talk about blueberries. We're going to cover how blueberries improve vascular function, how they protect the brain, improve glucose control, repair the gut, and may even help with exercise recovery.”
“even help with exercise recovery. Then there's the banana smoothie question: why I think leaving ripe bananas out of a blueberry smoothie is a reasonable optimization. By the end of this episode, you'll know where the benefits look most credible, where the science is still preliminary, and how to build a simple blueberry habit without turning this useful food into a miracle cure.”
“One cup of blueberries per day may be enough to measurably change how your arteries function and perhaps influence how your brain ages. Blueberries improve the ability of your arteries to relax and deliver more blood to the brain, heart, and working muscles.” Under review
“The brain findings are especially intriguing. Blueberry interventions have improved aspects of memory and cognition in older adults, while long-term observational data have linked regular blueberry intake to a slower rate of cognitive decline, equivalent to actually being around 1.5 to 2.5 years younger cognitively.”
“I still take a cautious approach when trying to maximize blueberry polyphenol exposure. Before we get into health outcomes, I do think it's important to understand what makes blueberries so biologically interesting. So, blueberries are often described as being high in antioxidants, but I do think that that can create the wrong mental model.”
“Then, it can terminate this chain reaction that ends in oxidation. Blueberry polyphenols can also do that. They can neutralize oxidants, but I think that's probably not their most interesting primary role in the human body. Most blueberry polyphenols circulate at relatively low concentrations and they're very much transformed by intestinal enzymes, by the gut microbiome, and also by the liver.”
“and on. So, let's talk about the major polyphenols that are actually found in blueberries. First and foremost, anthocyanins. These are generally the dominant class. These are actually the pigments that are concentrated in blueberry skin that produce that dark blue and purple color. One cup of blueberries commonly provides roughly around 160 to 385”
“One cup of blueberries commonly provides roughly around 160 to 385 milligrams of anthocyanins, although I would say that really depends on the cultivation of the blueberries, the types of blueberries that we're talking about here, the growing conditions, lots of things. However, anthocyanins also have the strongest direct human evidence, particularly for improving vascular function.”
“We're going to talk more about that later. The next class of polyphenols that I would say is the most abundant in blueberries is chlorogenic acid. These are the most abundant non-anthocyanin polyphenols that are found in blueberries.”
“In addition, blueberries also contain smaller amounts of free catechin and epicatechin, but these are definitely not the dominant polyphenols in blueberries. So blueberries really are not just delivering one type of polyphenol, one type of antioxidant molecule.”
“own metabolism. And it's those transformations, those metabolites that are formed that really explain why blueberries can affect systems as diverse and different as the arteries and the brain and the gut and even skeletal muscle.”
“So let's get into health benefits, starting with the brain. Not because this is where I think blueberry evidence is the strongest, the vascular evidence is stronger, but the brain is where I'm most interested. I think it raises a provocative question.”
“I'm most interested. I think it raises a provocative question. Something as ordinary as a cup of blueberries. Could you eat a cup of blueberries and change the trajectory of your cognitive aging? And I think that the evidence suggests that is possible.”
“Then there's the longer observational studies. These are associations. They're finding regular berry intake, regular blueberry intake is associated with slower cognitive aging. And then there is also separate cohorts that are linking higher blueberry intake or even just the dominant polyphenol in blueberries, the anthocyanin intake, with the lower risk of dementia and Alzheimer's disease as well.”
“You know, sometimes people associate this with brain fog, for example, although they're not necessarily the same thing. So across these randomized controlled trials, blueberries did produce a small improvement in what's called episodic memory. I've talked a lot about this in the past. Episodic memory really is just the ability to form and retrieve memories that are associated with specific events.”
“a couple of days earlier. Language-related memory also improved in those individuals that consumed the blueberry that had mild cognitive impairment. So there's two types of memory that improve, language-related memory and episodic memory.”
“So that's really all we have with respect to the randomized controlled trials with blueberries. Pretty promising, not a ton of data, but there's enough to really, I think, have a strong signal that something as small as a cup of blueberries a day does seem to improve various measurements of cognition and memory.”
“This was the nurse's health study. This is older women. They consumed at least a half a cup of blueberries per week. They also experienced a slightly slower rate of cognitive decline than women who rarely ate them. And investigators did estimate that the difference in cognitive decline was actually comparable to being approximately between 1.5 to two years younger cognitively.”
“cognitively. So that does not mean or prove blueberries are preventing dementia, but I do think it goes along with the randomized controlled trial story showing that perhaps, you know, these blueberries are affecting cognition.”
“We're talking about actually being diagnosed with dementia. So there's a long-running framingham analysis that found that people who consume blueberries at least occasionally had about one-third lower risk of dementia than people who rarely ate them.”
“And I do think these are pretty striking numbers. The blueberry intake, honestly, in my opinion, was surprisingly modest. So it was defined relative to other people in the cohort. It wasn't like a clear amount, like one cup per day. So the stronger findings also, I think, comes from the secondary analysis, right?”
“So there was one Framingham analysis that found relatively high anthocyanin intake. Remember, anthocyanins are the predominant polyphenol found in blueberries. High anthocyanin intake was associated with a 76% lower risk of Alzheimer's disease and related dementias.”
“I wouldn't focus on a single percentage here. I think the take-home here is that consuming more blueberries clearly is associated with a lower Alzheimer's disease risk and a lower dementia risk. The magnitude, we don't really know what that magnitude is.”
“Blueberries may influence that system, as we're going to discuss in detail in a moment, through improving endothelial function, improving nitric oxide signaling, insulin signaling, inflammatory regulation, actually, even changes possibly in neuronal activation.”
“There have been some small imaging studies that have reported an altered brain activation after blueberry supplementation, but cognitive improvements also do occur without changes in cerebral blood flow.”
“There's also been several animal studies. They've been feeding animals blueberry extract in mice, and they hint at other possible mechanisms. So there's the direct brain exposure mechanism, and this is where intact blueberry anthocyanins actually have been detected in the hippocampus and other brain areas in rodents, which is so interesting.”
“Another potential mechanism that's been shown in animal studies has to do with synaptic plasticity. So in aged rats, they were fed a diet that was about 2% blueberry powder for about 12 weeks, and that did improve spatial working memory. It increased activity among a variety of different hippocampal signaling pathways that are required for memory formation, that are required for memory retention.”
“And then there's also the lower neuroinflammation. So blueberry supplementation has been shown to reduce chronic microglial activation in mice. So microglia are actually the brain's resident immune cells, and you need them there.”
“And this brings us to the area where the human blueberry evidence I think is substantially stronger: the ability of the vascular system to respond to increased demand. I think one of the most robust claims we can make about blueberries is also more interesting than the usual language about quote-unquote antioxidants.”
“The evidence isn't there yet that eating blueberries is necessarily going to prevent strokes or prevent heart attacks. But if we look across controlled human trials, blueberries improve a physiological function that really does sit upstream of cardiovascular disease, and that is the ability of the endothelium.”
“And this is where the blueberry data I think is the most interesting and definitely the strongest. So there's two recent meta-analyses that I want to discuss.”
“just talking about one study, we're talking about many studies. So two different meta-analyses looked at blueberry consumption, generally about a cup of blueberries or equivalent to a cup of blueberries a day, and improved, again, this FMD flow-mediated dilation. It's really just the artery widening.”
“It's really just the artery widening. And what it found is that blueberry consumption was associated with about a 1 to 1.5 percentage point improvement in that FMD, in that response. It sounds small, but actually it's a pretty meaningful change.”
“Now, remember, the equivalent of about one cup of blueberries a day across multiple different randomized control trials, many, many. That was associated with improving one to 1.5 percentage points in that FMD response.”
“And I do think that this group provides kind of one of the clearest indications that the dose of blueberries also might matter. So the participants consumed either an equivalent of one cup of blueberries per day or a half a cup of blueberries per day or a match placebo.”
“per day or a match placebo. After six months, only those individuals in this trial that consumed the one cup of blueberries per day dose had meaningful vascular effects. And there were two of them that we saw improvements in.”
“Also in this study, this is important to point out, the half a cup equivalent dose of blueberries did not have the same vascular benefits as the full cup. It was the full cup that was required. So really, we don't know what the exact threshold is because there was only a half a cup or a full cup.”
“There wasn't anything in between. But I do think that what we can definitively say here is that a half a cup of blueberries a day or equivalent to a half a cup may not have these beneficial vascular effects.”
“They were given the equivalent of about one cup of blueberries per day, and it did improve their flow-mediated dilation response. So, their blood vessels did become better at dilating. However, other biomarkers of blood pressure, arterial stiffness, didn't change.”
“There's also observational evidence that supports this story on vascular health. It's not all blueberry-specific, some of it is anthocyanins, the predominant polyphenol found in blueberries. But mostly, these studies are looking at berry consumption.”
“So, you're having improved cardiovascular outcomes with more anthocyanin intake. We know that from randomized controlled trials, blueberry trials specifically, that we are improving endothelial function, which is really important for cardiovascular function. It has also been associated with lower cardiovascular events as well.”
“preservation and reduce oxidative suppression. This is from animal studies. So, I think this really creates this, you know, more cohesive story that blueberries really are improving endothelial function. They're decreasing cardiovascular disease risk, they're decreasing the events of cardiovascular events like heart attacks.”
“nitric oxide, it has to do with reducing oxidative stress as well. So, the totality of evidence really does signal that the equivalent of about one cup of blueberries per day is improving endothelial function and is associated with reduced cardiovascular events, cardiovascular disease, and cardiovascular mortality.”
“We need to widen, right? Blueberries appear to help preserve this nitric oxide-dependent response. And they may do that because the blueberry anthocyanins are converted to these metabolites that are actively influencing vascular signaling.”
“So the more anthocyanins produced a larger vascular response. When the anthocyanin dose was comparable to the amount supplied by whole blueberries, the improvement in that flow-mediated dilation was also comparable. But control preparations containing similar amounts of blueberry fiber, vitamins, minerals did not have the same effect. Now, pause.”
“So that aside, I also want to mention the effects extended beyond nitric oxide. Daily blueberry intake also changed the expression of more than 600 genes. I mean, crazy, 600 genes. It also changed the expression of three different, what are called microRNAs circulating in our immune cells.”
“them were associated with vascular function, 17 were doing a long-term response. It's just so cool and amazing, and so much more than just a blueberry, right? So much more than just a single polyphenol. I mean, it's changing so many different biological processes in our body.”
“I think that I want to switch gears and talk about metabolic health now. This is probably what you've heard a lot about with respect to blueberries and their health benefits. But I will say the metabolic data on blueberries is a lot more complicated than the vascular data, and it's also a little bit more interesting than the usual blueberries simply lower blood sugar.”
“fasting blood glucose levels. That's important to point out. With that said, I want to talk about one of the strongest blueberry studies that did test this directly. So, adults with obesity and with insulin resistance were given about the equivalent of approximately two cups of blueberries per day for six weeks.”
“Insulin sensitivity improved by about 22% in that blueberry group without any change in body weight or body fat. They became more responsive to insulin without losing weight.”
“Bruce Ames lab, I was involved in a clinical trial using blueberries. Actually, it was a freeze-dried blueberry powder in part to test whether we could reproduce this exact finding that I just told you about, the 22% improvement in insulin sensitivity.”
“It was a double-blind trial. It was in overweight adults that had insulin resistance. The participants in our trial consumed the equivalent of two cups of blueberries per day or a placebo powder. We measured glucose tolerance, we measured insulin resistance, we measured blood lipids, we measured inflammation, oxidative stress, DNA damage, a range of different metabolic pathways.”
“either a placebo or the equivalent of one cup of blueberries. The blueberries did not prevent the initial rise in glucose, but three hours later, the glucose was lower and insulin was less than half of that in the placebo condition.”
“required dramatically less insulin to get there. That does suggest that blueberries might alter later handling of a meal rather than just simply blocking or slowering the initial absorption of, you know, the carbohydrate, for example.”
“body's own gut hormone and nutrient sensing pathways. And I do think that may help explain why the metabolic effects of blueberries are often easier to detect after a meal or in someone who already has insulin resistance rather than just looking at fasting blood work or looking at a metabolically healthy person.”
“person. So let's talk about the observational evidence because it does point in the same general direction. There were three different large cohorts that found every additional three servings of blueberries per week was associated with a 26% lower risk of developing type 2 diabetes.”
“response. But this is just a correlation. So where do I land on blueberries and metabolic health? I think this is where the evidence is very credible that they do improve insulin sensitivity in some people with insulin resistance.”
“a substantial challenge. For practical protocols, it really seems in general approximately one cup of whole blueberries per day is a reasonable place to start, ideally consumed with a meal or used to replace a refined carbohydrate dessert, right?”
“day really seems to be the standard. Now I want to shift gears and talk about the gut. And I do think the gut may be one of the most important and most misunderstood places where blueberries act. We often hear things like blueberries feed good bacteria.”
“And that may be true, but I think it misses the more interesting biology. The microbiome does not simply just respond to blueberry polyphenols. It transforms them into entirely new compounds. Only a small portion of blueberry anthocyanins is absorbed intact.”
“Some of the compounds that ultimately reach our blood after eating blueberries are actually manufactured by the bacteria in our gut. So what does that mean? Part of the vascular effects, the metabolic effects, and even perhaps some of the cognitive responses to blueberries may actually begin in the colon.”
“gastrointestinal disorders. They consumed about 30 grams of freeze-dried blueberry powder. That was equivalent to a little more than a cup a day of fresh blueberries for six weeks. And they also completed a match placebo control period in a randomized crossover design.”
“So the same people were consuming either the blueberry powder or the placebo powder. During the blueberry part of the trial, 53% of those people reported clinically meaningful relief of abdominal symptoms compared to the 30% during the placebo period.”
“That trial was in older adults that had overweight or obesity. They consumed the equivalent of about one and a half cups of blueberries per day for about 12 weeks. And there was really no broad transformation of the gut microbiome, but there was an enrichment of a bacterial group that helps metabolize dietary polyphenols.”
“So it may be that blueberries are fine-tuning the microbiome function more than rebuilding the entire community. So the gut mechanism becomes especially interesting at the intestinal barrier.”
“In rodent models of diet-induced obesity, blueberry powder increased muc2 expression by approximately 150%. It also restored the intestinal villi height.”
“So now I'm going to shift gears and talk about exercise performance and recovery. And I think one of the more interesting questions is whether blueberries can improve exercise performance or whether their real value is in improving exercise recovery. We know hard workout is a controlled biological stressor.”
“You want those adaptations to the stressor to happen. So this is where blueberries come in. Blueberries do not appear to be a reliable performance enhancer in most cases. If you look across the human data, they have not consistently improved speed, endurance, soreness, or even any other conventional markers of muscle damage.”
“If we start by looking at one crossover study in women, these women consumed repeated blueberry smoothies before and after a bout of damaging eccentric exercise.”
“of damaging eccentric exercise. Blueberries did not prevent the initial muscle damage or strength loss, but muscle strength returned faster. More recent studies may help explain why.”
“So in two separate clinical trials, consuming approximately the equivalent of one cup of blueberries per day for about two or three weeks shifted the post-exercise oxylipin response.”
“weeks shifted the post-exercise oxylipin response. So several pro-inflammatory signals were lower, while some omega-3 derived signals involved in inflammation resolution were actually higher after blueberry consumption.”
“The participants didn't necessarily feel less sore, and blueberries didn't really prevent the initial decline in muscle function. So the evidence isn't that blueberries are eliminating exercise-duced inflammation, which is good.”
“They're resolving the inflammation more efficiently, and that's really what you want. So obviously, I'm not saying that blueberries replace carbohydrates during prolonged exercise. They're not going to replace adequate protein after resistance training or sleep.”
“We tend to think of digestion beginning after we swallow food. So we chew it and we swallow it. But if we're making something like a blueberry smoothie, some of the chemistry begins in the blender. Breaking open plant cells can bring enzymes in from one ingredient into direct contact with the polyphenols from another.”
“But the question that I'm asking is actually much more narrow. And that question is, what happens to blueberry polyphenols when blueberries are blended with a food that contains a very high activity of an enzyme called polyphenol oxidase?”
“kilo units in avocado or 12 units in a high blueberry bush. So you're talking about 136 times more PPO activity in a banana compared to an avocado and about 270 times more activity than that found in a high blueberry bush blueberry.”
“than that found in a high blueberry bush blueberry. That's a pretty big difference. It's enormous actually. And that's why the banana becomes relevant in this story that we're going to talk about.”
“And it's not that the bananas are unhealthy. It's that when a banana is blended with a polyphenol rich food like blueberries, it can bring a very large amount of enzymatic activity in direct contact with those compounds.”
“enzymatic activity in direct contact with those compounds. So the next question is, which blueberry polyphenols can PPO actually oxidize? What are the direct PPO substrates? This is where the distinction between direct and indirect targets becomes very important.”
“Blueberries contain these compounds, although they are not the dominant polyphenols in blueberries. The strongest human evidence for banana interaction does involve epicatechin, and we'll get into that later.”
“So the chlorogenic acid is often the most abundant non-anthocyanin polyphenol in blueberries. Banana PPO enzyme directly targets them. It directly oxidizes them. And when that happens, chlorogenic acid is converted into that highly reactive compound I referred to earlier called a quinone.”
“When that quinone forms, and if you look in a blueberry model system, which has been done, anthocyanins don't get targeted by the PPO enzyme when they're tested alone.”
“reacts with anthocyanins. In that blueberry model, approximately two anthocyanin molecules were degraded for every one chlorogenic acid molecule oxidize.”
“So PPO does not directly need to bind to anthocyanin directly to affect it. It can oxidize other blueberry polyphenols first, generate a reactive quinone, and that quinone then degrades the anthocyanins. As we have been discussing, anthocyanins are the dominant polyphenols in blueberries. They have the strongest human evidence for many of the vascular benefits.”
“What we do not yet know is how much of that chemistry occurs in actual banana blueberry smoothie or how much it changes the physiological benefits of the blueberries themselves.”
“changes the physiological benefits of the blueberries themselves. No research has ever looked into that important question or these important questions. But it does give us a strong mechanistic reason to take the interaction seriously.”
“It was a very large banana, and they blended it with almond milk. They compared the high PPO drink with a low PPO mixed berry smoothie, which had berries, blueberries, strawberries, blackberries, and raspberries. Both drinks also contained the same standardized dose of cocoa extract.”
“So this is not a direct test of every polyphenol on blueberries. It was a very controlled test of what the banana PPO enzyme does to epicatechin. It is one polyphenol that is in blueberries in a small amount.”
“And we do know that PPO directly oxidizes that polyphenol. So the banana smoothie contained about 93 times more PPO activity than the mixed berry smoothie. That effect is very striking. After the banana smoothie, peak levels of epicatechin derived metabolites were 84% lower and total exposure over six hours was 81% lower”
“However, I do want to clarify the headline. This was not an 84% reduction in all blueberry polyphenols. It was not an 84% reduction in the anthocyanins or blueberry health benefits. It was an 84% reduction in the peak blood concentrations of epicatechin-derived metabolites, primarily from cocoa extract that was added to the drink.”
“ultimately reaches the circulation. As I mentioned earlier, epicatechin is present in small amounts in blueberries, but epicatechin is not the only blueberry-relevant polyphenol that banana PPO can oxidize. As I also mentioned earlier, other studies done in blueberry models found that chlorogenic acid does interact and is”
“anthocyanins indirectly. That is why the broader blueberry question remains biologically plausible, even though it hasn't yet directly been tested in people. So, where does the totality of evidence leave us?”
“I think there are several things that are now well established. One, PPO directly oxidizes a number of dietary polyphenols that are present in blueberries, including chlorogenic acid, caffeic acid, catechin, epicatechin.”
“PPO enzyme was inhibited. What has not been measured is the complete blueberry question. We do not yet know how much blueberry chlorogenic acid or anthocyanin is altered when banana and blueberries are blended together. And no study has tested whether that interaction changes the vascular or the cognitive or the metabolic or the gut or the exercise-related benefits from blueberries.”
“effective dose to have the health benefits. So when I make my blueberry smoothie, I am trying to maximize the polyphenols, and therefore I leave out the banana because it has high PPO activity. I swap it with an avocado, which has low PPO activity because I like the creaminess.”
“I think someone else might reasonably decide they like the taste of the banana. They like to add bananas to the blueberry smoothies and they're going to continue to do that. That's fine. I think the accurate message here is that banana PPO does reduce exposure to susceptible polyphenols like epicatechins.”
“We also know that it oxidizes chlorogenic acid, which is high in blueberries, and that those quinones that are formed from the epicatechins and the chlorogenic acid do affect anthocyanins.”
“epicatechins and the chlorogenic acid do affect anthocyanins. They degrade anthocyanins. We know it does in a blueberry model system. And I think that gives us a reasonable basis for caution, even though the precise effect on blueberry health benefits has not yet been measured.”
“I'm choosing not to blend them with my blueberry smoothie. I'm deliberately trying to maximize for polyphenols. But the banana question really is only a small part of a much bigger story. The more important takeaway here from this episode is what blueberries themselves can do when they are consumed consistently and across the brain, the vascular system, metabolism, gut, exercise recovery.”
“The strongest benefit is vascular. Blueberries improve the ability of the arteries to sense increased blood flow and respond by dilating. That matters not only for cardiovascular health, but also for the brain, which depends on rapid delivery of oxygen and glucose and all kinds of goodies whenever neurons become active.”
“The brain data is also compelling. In older adults, blueberries have improved aspects of memory and cognitive flexibility. Long-term observational studies associate regular blueberry intake with slower cognitive aging. The metabolic effects appear most clearly when the system is under strain. So, blueberries seem to help people that are insulin-resistant.”
“And after demanding exercise, blueberries may help shift inflammatory signaling toward resolution and recovery. What ties these effects together is that blueberry polyphenols are not only acting as antioxidants that mop up free radicals, anthocyanins and their metabolites function like signaling molecules.”
“So, my practical recommendation is pretty straightforward. We can consume approximately one cup of whole, fresh, or frozen blueberries per day consistently. We can add them to yogurt, to oatmeal, we can eat them by themselves, blend them in a smoothie. And the larger takeaway is that these blueberries are worth eating.”
“It's a dose that's practical, affordable, it's easy to sustain. They can measurably improve vascular function and they may support brain health, improve metabolic resilience, gut biology, exercise recovery, and more. And they're delicious.”
“even help with exercise recovery. Then there's the banana smoothie question: why I think leaving ripe bananas out of a blueberry smoothie is a reasonable optimization. By the end of this episode, you'll know where the benefits look most credible, where the science is still preliminary, and how to build a simple blueberry habit without turning this useful food into a miracle cure.”
“I will also revisit the controversial blueberry and banana smoothie question: what the evidence really shows, where the uncertainty remains, and why I still take a cautious approach when trying to maximize blueberry polyphenol exposure.”
“Under certain conditions, it's actually kind of becoming this reaction chamber. And this is where bananas enter the story. Before we get into the banana-blueberry interaction, I want to be very clear. Bananas are a healthy food. A medium banana provides roughly three grams of fiber.”
“We all know that Americans fall short in the recommended fiber intake. So as a snack, a banana is a much, much better choice than any other ultra-processed food that comes in a package. But the question that I'm asking is actually much more narrow.”
“of an enzyme called polyphenol oxidase? Bananas have an enzyme in them called polyphenol oxidase. So what exactly is that enzyme? Polyphenol oxidase, or PPO for short, it's an enzyme that is found in many plant foods, including bananas, apples, potatoes, avocados, even berries.”
“So a banana turning brown is essentially that polyphenol oxidase chemistry that you can see. When the plant cells are disrupted, the polyphenol oxidase or the PPO becomes in contact.”
“So in one assay that was used by smoothie investigators, PPO activity was approximately 3,258 kilounits per 100 grams in banana compared with only 24 kilo units in avocado or 12 units in a high blueberry bush. So you're talking about 136 times more PPO activity in a banana compared to an avocado and about 270 times more activity than that found in a high blueberry bush blueberry.”
“And it's not that the bananas are unhealthy. It's that when a banana is blended with a polyphenol rich food like blueberries, it can bring a very large amount of enzymatic activity in direct contact with those compounds.”
“So banana polyphenol oxidase can directly oxidize polyphenols like epicatechin, catechin, and related what are called flavin-3-ols. Blueberries contain these compounds, although they are not the dominant polyphenols in blueberries.”
“The strongest human evidence for banana interaction does involve epicatechin, and we'll get into that later. But I do want to talk about the more consequential direct target for blueberries may actually be chlorogenic acid.”
“So the chlorogenic acid is often the most abundant non-anthocyanin polyphenol in blueberries. Banana PPO enzyme directly targets them. It directly oxidizes them. And when that happens, chlorogenic acid is converted into that highly reactive compound I referred to earlier called a quinone.”
“They have the strongest human evidence for many of the vascular benefits. So the argument that banana PPO enzyme only affects a relatively small amount of free epicatechin in blueberries is not accurate. It's incomplete. What we do know is that the banana PPO enzyme can directly oxidize epicatechin.”
“What we do not yet know is how much of that chemistry occurs in actual banana blueberry smoothie or how much it changes the physiological benefits of the blueberries themselves.”
“systems. But when we ask the human question, does consuming a high PPO food such as a banana actually reduce how much of a susceptible polyphenol reaches the circulation?”
“This study was published in 2023. Researchers blended about 177 grams of a ripe banana. It was a very large banana, and they blended it with almond milk. They compared the high PPO drink with a low PPO mixed berry smoothie, which had berries, blueberries, strawberries, blackberries, and raspberries.”
“So this is not a direct test of every polyphenol on blueberries. It was a very controlled test of what the banana PPO enzyme does to epicatechin. It is one polyphenol that is in blueberries in a small amount. And we do know that PPO directly oxidizes that polyphenol.”
“And we do know that PPO directly oxidizes that polyphenol. So the banana smoothie contained about 93 times more PPO activity than the mixed berry smoothie. That effect is very striking. After the banana smoothie, peak levels of epicatechin derived metabolites were 84% lower and total exposure over six hours was 81% lower”
“than the same compounds that were taken in the capsule without the banana smoothie. In contrast, the low PPO berry smoothie produced epicatechin levels similar to the capsule.”
“So in this part of the study, 11 men alternated sips between two drinks. The banana and the epicatechin were not actually mixed together beforehand, like in the previous study that they did. Even then, though, the blood levels of the epicatechin metabolites were 37% lower, which did suggest that the interaction continued after swallowing.”
“Then, the researchers went on to look at the mechanism, and I think that was also very convincing. So, in the blended banana drink, half of the epicatechin disappeared in less than 10 minutes at room temperature. When the researchers inhibited the PPO enzyme, that disappearance was prevented.”
“banana smoothie or whatever. It was the PPO enzyme that was driving that interaction. However, I do want to clarify the headline. This was not an 84% reduction in all blueberry polyphenols.”
“ultimately reaches the circulation. As I mentioned earlier, epicatechin is present in small amounts in blueberries, but epicatechin is not the only blueberry-relevant polyphenol that banana PPO can oxidize. As I also mentioned earlier, other studies done in blueberry models found that chlorogenic acid does interact and is”
“a direct target from PPO enzymes that are found in bananas, and the quinones that are formed from that reaction then degrade anthocyanins indirectly. That is why the broader blueberry question remains biologically plausible, even though it hasn't yet directly been tested in people.”
“And in that one human publication, a high PPO banana smoothie produced a very large reduction in circulating epicatechin derived metabolites from cocoa extract. So this was found in human circulation, right?”
“PPO enzyme was inhibited. What has not been measured is the complete blueberry question. We do not yet know how much blueberry chlorogenic acid or anthocyanin is altered when banana and blueberries are blended together. And no study has tested whether that interaction changes the vascular or the cognitive or the metabolic or the gut or the exercise-related benefits from blueberries.”
“a cup did not produce the same effect. So I'm not sure. That doesn't prove that adding banana removes enough polyphenols to eliminate the benefit, but it does tell us that you need an effective dose to have the health benefits. So when I make my blueberry smoothie, I am trying to maximize the polyphenols, and therefore I leave out the banana because it has high PPO activity.”
“I personally like that. It's not because I think bananas are unhealthy. It's just an optimization decision based on the chemistry we currently understand. I think someone else might reasonably decide they like the taste of the banana.”
“They like to add bananas to the blueberry smoothies and they're going to continue to do that. That's fine. I think the accurate message here is that banana PPO does reduce exposure to susceptible polyphenols like epicatechins. We also know that it oxidizes chlorogenic acid, which is high in blueberries, and that those quinones that are formed from the”
“yet been measured. So, where do I land on the banana question? I am not avoiding bananas. I'm choosing not to blend them with my blueberry smoothie. I'm deliberately trying to maximize for polyphenols. But the banana question really is only a small part of a much bigger story.”
“So in one assay that was used by smoothie investigators, PPO activity was approximately 3,258 kilounits per 100 grams in banana compared with only 24 kilo units in avocado or 12 units in a high blueberry bush.”
“it has high PPO activity. I swap it with an avocado, which has low PPO activity because I like the creaminess. I like the monounsaturated fat, which increases the bioavailability of some of the other components that I add to my smoothie, which is kale.”
“and found that those that had the highest intake of anthocyanins, and this is from a variety of different berries, had a 26% lower cardiovascular disease incidence, an 18% lower risk of having a heart attack, a 9% lower cardiovascular-related mortality, 8% lower hypertension incidence, and there was no significant reduction in stroke.”
“It was a very large banana, and they blended it with almond milk. They compared the high PPO drink with a low PPO mixed berry smoothie, which had berries, blueberries, strawberries, blackberries, and raspberries. Both drinks also contained the same standardized dose of cocoa extract.”
“There was another interesting, what I think is an interesting 12-week trial that gave older adults, again, the equivalent of around one cup of wild blueberries per day. And at the end of the 12 weeks, the blueberry group did recall more words immediately after hearing a list of words. And they also performed better on a task that required them to rapidly switch between different rules.”
Also filed under Blueberries
“The microbiome findings themselves have been a little bit more subtle. If we look at a different study, this was a six-week study, it used about one cup of wild blueberries per day. That study found an increase in bifidobacterium in some participants, but the response, there was a lot of individual variation, right?”
“There's also been several animal studies. They've been feeding animals blueberry extract in mice, and they hint at other possible mechanisms. So there's the direct brain exposure mechanism, and this is where intact blueberry anthocyanins actually have been detected in the hippocampus and other brain areas in rodents, which is so interesting.”
“It's also the predominant polyphenol found in coffee. I've talked a lot about coffee in the past as well. The chlorogenic acid also contributes to vascular, metabolic, and some of the microbial effects that we're going to talk about today.”
“risk of developing type 2 diabetes. Fruit juice actually moved in the opposite direction. It increased type 2 diabetes risk and it really comes down to the food matrix is really important for slowing the glucose response. But this is just a correlation.”
“is kale. It has lutein and zeaxanthin. It's been shown to increase the bioavailability of those compounds by fourfold. It also has higher levels of potassium and other micronutrients and has more fiber. I personally like that.”
As referenced on air, with the quote and the moment. Reported, not evaluated.
“So there's two recent meta-analyses that I want to discuss... two different meta-analyses looked at blueberry consumption, generally about a cup of blueberries or equivalent to a cup of blueberries a day, and improved, again, this FMD flow-mediated dilation.”
“There was another meta-analysis of 35 different studies that found for each one percentage point higher in the FMD, that was associated with about a 12% lower risk of future cardiovascular events, like heart attacks, like strokes.”
“This was a six-month randomized controlled trial in adults with metabolic syndrome... the participants consumed either an equivalent of one cup of blueberries per day or a half a cup of blueberries per day or a match placebo.”
“This was a 12-week trial that was in postmenopausal women that had elevated blood pressure. They were given the equivalent of about one cup of blueberries per day, and it did improve their flow-mediated dilation response.”
“There was a systematic review and meta-analysis of many different studies that compared the highest intake of anthocyanins with the lowest intake and found that those that had the highest intake of anthocyanins, and this is from a variety of different berries, had a 26% lower cardiovascular disease incidence”
“adults with obesity and with insulin resistance were given about the equivalent of approximately two cups of blueberries per day for six weeks. Researchers then measured insulin sensitivity using something called the hyperinsulmic euglycemic clamp... Insulin sensitivity improved by about 22% in that blueberry group”
“I have a very personal connection to this study because during my postdoctoral work in Dr. Bruce Ames lab, I was involved in a clinical trial using blueberries... what we did is that we conducted an eight-week clinical trial. It was a double-blind trial. It was in overweight adults that had insulin resistance.”
“we conducted an eight-week clinical trial. It was a double-blind trial. It was in overweight adults that had insulin resistance.”
“There was also a 2026 dose response study that provided a potential mechanism. So when healthy adults consumed higher doses of wild blueberry anthocyanins with a carbohydrate rich breakfast”
“There was the 2025 B active trial. That trial was in older adults that had overweight or obesity.”