Which diets and foods work best for blood pressure?

Ever pondered how to navigate the vast sea of research on diets and blood pressure without losing your way? Join us as we uncover the layers of a recent Advances in Nutrition paper, presenting a valuable guide for healthcare professionals in the integrative medicine field. 

Embarking on systematic reviews in dietary research often feels like embarking on a quest for the Holy Grail. In this installment, we express appreciation for the diligence required to scrutinize thousands of studies. Balancing admiration with a critical eye, we meticulously examine the utilization of tools such as AMSTAR and the Cochrane Risk-of-Bias to separate valuable insights from less substantial findings.

Aljuraiban GS, Gibson R, Chan DS, Van Horn L, Chan Q. The Role of Diet in the Prevention of Hypertension and Management of Blood Pressure: An Umbrella Review of Meta-Analyses of Interventional and Observational Studies. Adv Nutr. 2024 Jan;15(1):100123. doi: 10.1016/j.advnut.2023.09.011. Epub 2023 Oct 1. PMID: 37783307; PMCID: PMC10831905.

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Transcript

Introducer: 0:02
Welcome to the Doctor Journal Club podcast, the show that goes on to the hood of evidence-based integrative medicine. We review recent research articles, interview evidence-based medicine thought leaders and discuss the challenges and opportunities of integrating evidence-based and integrative medicine. Continue your learning after the show at www. drjournalclub. com.

Josh: 0:31
Please bear in mind that this is for educational and entertainment purposes only. Talk to your doctor before making any medical decisions, changes, etc. Everything we're talking about that's to teach you guys stuff and have fun. We are not your doctors. Also, we would love to answer your specific questions. On www. drjournalclub. com you can post questions and comments for specific videos, but go ahead and email us directly at josh at drjournalclub. com. That's josh at drjournalclub. com. Send us your listener questions and we will discuss it on our pod. 

Hello everyone and welcome to the Doctor Journal Club podcast where today we're going to talk about the length of Adam's hair. Adam, do you want to share what you were just saying before we started?

Adam: 1:21
Growing out my hair. Yep, I haven't cut it since October.

Josh: 1:25
Okay, nice.

Adam: 1:26
This is a journey that we're all going to go on together. Uh-huh, uh-huh yep and a lot of self-discovery here.

Josh: 1:33
So I think we should do, we should take bets, so listeners should call in and perhaps make a bet on when you finally fold on total length. And then I think you were saying your podmates are also doing this together, so who has the fastest growing hair? Is that the idea? Or the most ridiculous length at the end of time? What is the end point? What is the clinically meaningful end point here?

Adam: 1:58
We haven't gotten there.

Josh: 2:00
You don't have a protocol. You haven't figured anything out, have you ?

Adam: 2:07
Ad hoc we change the protocol.

Josh: 2:10
Yeah, classic. So I suggested that you go for shoulder length or something, or maybe-.

Adam: 2:17
I'm saying Joe Dirt. I think we're going Joe Dirt style.

Josh: 2:27
I don't know Joe Dirt. Should I watch it.

Adam:
You haven't seen Joe Dirt? Google it real quick, like right now. Everybody Google Joe Dirt, yeah, joe.

Josh:
Oh wow. Okay, that's what we're going yeah, that's something, that's really something. Okay, that's like fancy mullet. That's a very evolved mullet, okay.

Adam: 2:42
The mullets are coming back, man.

Josh: 2:43
Well, no, they're not. They're absolutely not. 

Adam: 2:49
I got my Bieber here, we'll get my mullet and then we'll set a wall.

Josh: 2:52
All right. I'm calling this conversation now. We got to get in before we lose anybody else. But, in all seriousness, listeners, we need feedback and you need to post pictures, I think, on social media, as this evolves.

Adam: 3:08
Can I wear a bright track top because we're bringing the 80s back.

Josh: 3:14
But before the show, Adam was like he's got a clinic pager now, right. So he's like Josh, you lived through the 80s, right? I've never felt so old to get that question. He's like how do I shut off this beaver? And so, okay, final thing is, my son will now regularly ask me well, was this in the 80s? Did this happen in the 80s? Like back in the 80s Back in the 80s. Anyway, we're moving on now. Listen, gentlemen, did you? have cars back in the 80s? No, but it's like mind blowing to him that we didn't have cell phones. We were watching. Okay, last comment, listeners please. I promise we're going to talk medicine in a second. But last comment we finally got him to stop watching Disney stuff and we're like they're classic movies and so we put on Honey, I Shrunk the Kids and I don't know if you remember that, but the kids are not. The parents come home from school and the kids are not there and they're just like, oh, it's cool, they're probably at the mall. So the mom goes and drives to the mall to look for them and it was just like mind blowing to Theo that they couldn't like call them on their cell phone and figure out where they were and if they were safe at. The mom was literally driving around town, stopping at the mall which was also like a classic 80s, 90s thing to see where her children were when they were missing and shrunk to the sides of ants. Anyway, we digress upon other digressions. All right, we're going to talk science, dear listener, we're talking about blood pressure today. We're talking about diets, we're talking about the impacts of diets on blood pressure and we're talking about umbrella reviews. So with that segue, Adam, how would you like to start off our professionally produced helmet, the helm hosted podcast on evidence and integrative medicine.

Adam: 5:10
You know, I don't know how to respond to that.

Josh: 5:14
But because we just can't do it.

Adam: 5:16
But what we will do is we'll talk about paper that was published in the Advances in Nutrition. Thank you, and actually this year.

Josh: 5:24
I finally picked up the ball on that one.

Adam: 5:26
Yeah.

Josh: 5:27
Yeah yeah, this is the recent one, so this is cool. So full disclosure. The NAPCP, which is the Naturopathic Association of Primary Care Physicians. Now they asked me to present on blood pressure and integrated medicine and I was like, okay, cool, yeah, I'll see if I can find something. And I found this and I was like, okay, this is awesome. Why don't we do this on your own club, which will force me to read it and prepare for the presentation, which I've learned is not you shouldn't call it killing a bird with killing two birds with one stone, but rather feeding two birds out of one hand. A patient told me that the other day. I loved that. I thought that was great. All right, moving on. So this was an umbrella review, Adam. What is an umbrella review? What does that bring to mind?

Adam: 6:15
Basically it's a review of reviews. So when we have like a meta analysis and we're looking at like a pooling together a number of studies, like let's say, 20 randomized controlled trials of an intervention, and we want to know okay, we have these 20 trials If we were to synthesize all the data, what is all of that kind of showing? What is that one data point for the magnitude of effect? And when we have several systematic reviews or multiple meta analyses of the same question, we can do the same thing, where we basically do a meta analysis of meta analyses to come up with one treatment effect.

Josh: 7:00
Yeah, I would clarify and say a systematic review. Of systematic reviews you usually don't see, they usually won't meta analyze other meta analytic data, but because usually, like what you're doing so, you're systematically reviewing other systematic reviews and it's useful in situations like this where you have multiple different interventions or different populations or there's something different where you wouldn't quantify it all together like in a systematic, in a meta analysis. But you want to describe them side by side, discuss quality stuff like that. It's almost like you know if, like, a systematic review is seeing the forest from the trees, like it's like zooming back and like seeing the biome or something like that, or like earth, like you just want to get like an overall lay of the land using systematic reviews as your primary data point, as opposed to the primary literature, like the randomized trial or observational study or something like that. So yeah, so exactly. So this was an umbrella review. Let's see, let's just go through the methods here and then we can jump into some of the results which I think were interesting. What first thing is they followed the Joanna Briggs Institute methodology. That's a gold star in my book, sort of them and Cochrane are the main guidance providers for systematic reviews, and Cochrane kind of. You know they kind of bogart the standard systematic review and maybe you know individual participant data stuff. But everything else in the evidence synthesis world like the guidance on that pretty much comes out of the Joanna Briggs Institute. So they've done a lot on umbrella reviews, which is great. So that was awesome. They registered it with Prospero. You want to tell us a little bit about Prospero registrations, all that jazz.

Adam: 8:49
Yeah, so with Prospero, basically it's the clinical trials, that gov version of systematic reviews and meta analyses. When you're going to do a systematic review, you also want to register that a priori, meaning prior to actually conducting the review. You want to register it. This way, everyone knows how you're going to do the review, what you're looking for, etc. Etc. I've registered my meta analyses and systematic reviews in Prospero when I was publishing them. You have as well, and it's a very easy to access place to look at what not only what systematic reviews have been registered, but what other people are actually currently studying. So it's also good practice. I have this question that I want to answer. I don't know if there's been a systematic review on this. I can't find any literature to let me see Prospero and see if anyone's actually doing this already, which is actually really good, because you don't want to put all that time and effort into making a systematic review when there's one that's already in process of being done.

Josh: 9:56
Yeah, it's a good point. I don't use it that way and I totally should. And I think there's even a question when you're trying to register your study, like have you done a search and is someone else already doing this work essentially, which I think is you know to your point not to be duplicative Very cool, okay. So they register, which is great so far, like A plus with everything. Their literature search. They search multiple databases PubMed, m-base, web of Science, cock and Register, and I don't see any gray literature search. So maybe that's a little bit of a strike against them, but they've done a number of good databases, you know, maybe there's maybe missing would be Epistemoticos, which is like a database of evidence synthesis and systematic reviews, but otherwise I'd say this is pretty good and they're looking for systematic reviews and meta-analyses of randomized controlled trials but also of observational studies. So they're going to be inclusive of both of those.

Adam: 11:01
Which I think is actually appropriate, because, when it comes to studying diet, a lot of the times you're looking at dietary patterns yes, and it's kind of hard to to randomize someone to, let's say, like a Mediterranean diet, because there's no specific way of providing the Mediterranean diet. If that makes sense, like yes, you can standardize them to say like hey, aim for this number of servings of fruits and vegetables and limit animal fats and have more olive oil and whatnot, but ultimately, it's a dietary pattern that includes, like hey, it's a style of eating, as opposed to a specific intervention. If you will, yeah.

Josh: 11:40
So let's take a little bit of time on this, because I got into the weeds on this really crazily with a study we published recently which was also an umbrella review on saturated fats, and so, yeah, so there's like it used to be like back in the day, like you were to be interested in like saturated fat, like a macronutrient essentially, or even a micronutrient, and to see what the effect that was. And then people were like, well, that's stupid, you don't eat macronutrients, you eat food. And so then it was like, okay, we're going to do studies on eggs and red meat and things like that. And then it was food based. And then people were like, well, that's dumb, people don't eat food, they eat in dietary patterns and like that's. My understanding is like that's where nutrition research is going these days is focused more on these, just like you said, these dietary patterns which are a little more amorphous, but we group them into things like the Mediterranean diet, the dash diet and things like that. And you can do randomized trials, like prety med was a randomized control trial of the Mediterranean diet, but there's lots of problems with it. To your point, right, and like it's essentially what you said, like you give people guidance, you train them. Maybe you provide nuts or olive oil, I think in this example. But for the most part, like you're doing observational studies of dietary patterns, which you know, there's pros and cons. Like the observational studies it's more real life In the RCTs there's less bias and it's just. You need both essentially to get a good picture, I think, of dietary research.

Adam: 13:15
Yeah, I would agree.

Josh: 13:17
Cool, all right. So we're doing so. We're looking for systematic reviews and meta analyses and they are inclusive of all this stuff, right, they're looking for whether it's micronutrient, macronutrient, specific foods or dietary patterns. They're looking at all of that as it relates to both reducing blood pressure so like someone like a hypertensive population reducing blood pressure but also the risk of developing hypertension, so in like high risk or primary prevention environments. Basically like what's the relative risk grads ratio if you do this diet and then develop hypertension versus not? So they're looking at both of those, which I think is cool and they're trying to pull now. This is interesting, like if you're pulling every systematic review ever done on eggs for high blood pressure, you're gonna get multiple usually multiple systematic reviews, multiple meta-analyses, and they're gonna have overlapping coverage, right. So you might have one done in 2017 that was excellent quality, but you know you've got a new one done in 2024 that is up to date, but maybe the quality is not so good. Or maybe you have two done in 2023, and you know there's like 50% overlap, but you know there's still covering, because the searches were different or something like that. And like that's a big debate in umbrella research. It's like what do you include? How do you describe overlap? And it's a real pain in the behind. But I think what, what these folks did, which was interesting, very pragmatic I thought, was they basically took the. They. If there was multiple systematic reviews, meta-analyses on a specific food, they would take the one that had the most data. I think is how they kind of defined it. And they were very they seemed to be very methodical in how they defined that and you know, first we would look for this and then we would look for that, and if there was a tie, we would do this, and so I was. I thought that was reasonable in terms of like what you do in a situation like that.

Adam: 15:22
Yeah, yeah, I agree. And for those who are listening, when they were looking at the number of studies, they started off with just over 17,000. Yeah, and ended up looking at 175. Yeah, this is massive. Like this was a massive undertaking.

Josh: 15:38
And I was feeling bad for myself. We're in the middle of a review that had 21,000, as 21,000 citations we have to review as before, like secondary searching, and I'm like, yeah, it's like driving me crazy. And they had about that number. But, like, the full text that they went through was like what was it? It was something like a thousand full text articles they went through yeah, 1,277. 1,277, yeah, can you even imagine Like I would, just I'd shoot myself in the head. I cannot even imagine. And it's not like they even had a massive team and they went through 1,277 full text papers. So hats off to them. Like this is a prolific field Dietary systematic reviews, apparently, and so yeah, go ahead. Or they just use chat GPT and said to summarize it Review these 1,277 publications and summarize them? Yeah, that would be. That would be interesting. I wonder. You know, I hope that there's the dream that something like that is possible. Like, ai has changed the way we do abstract and title screening, but it's not quite there yet for full text screening, but one day soon, like. One day soon like when we're better at PDF and they're doing it. They're actively doing that research, but currently not so much. I think that was human and at least they didn't say otherwise. Okay so they have. This is massive, right, it's really massive. And, like you said, like, actually they have 175 papers that are included, which is just insane. So what other things? Methods wise. Okay, so they got all these studies. They looked at the quality of the study and so the way we think about quality here, there's like three levels of quality. So there's the quality of the systematic review itself, like was it well done? Did it do everything? Right, and that's am star, that's am star. Two is what we use for that. Then there was the quality of the evidence right, so you could have a crummy systematic review that's describing the Mediterranean diet, that claims that there's high level evidence that the Mediterranean diet works, for example. Right. So the quality of the systematic review and the quality of the evidence are not the same and, conversely, you can have a great systematic review that found that, yeah, the evidence for eggs is super weak and low right, so that's sort of different things. And then, of course, within the systematic reviews, they need to assess the evidence of the studies, the individual primary literature studies, and that's usually done with, you know, cochrane-riske-bias tool or Ottawa, what is it? Brown Ottawa, black, black Ottawa, I can't remember. There's a few of them for observational studies that people will use. Okay, so that's what we're talking about with quality and cool, I think we can jump into results. Oh, minimal, important difference, let's talk about that. So they also. Yeah, I like that. You want to talk a little bit about the MIT for this?

Adam: 18:39
Yeah, they said that basically dietary exposures that reported a clinically significant change in blood pressure were identified and what they considered to be clinically significant was anything greater than three millimeters of mercury. I thought that was kind of low.

Josh: 18:53
Yeah, I did too.

Adam: 18:54
Yeah, I wish they would have expanded upon that as to why they view that as clinically significant. It seemed a little bit arbitrary. Yeah, I for me I think like the absolute floor minimum should be five. It really like a like five to 10 would would be something that would be significant to me.

Josh: 19:17
Yeah, like like gut check as a clinician, that's what I would be looking for. And they don't have any citation for where they got three from. Maybe that is a standard. Lee accepted MIT, but I didn't. You know. Quick searching online I didn't see that. And yeah, they don't provide any citations. That's hard to say. I mean, I like that they talk. They're talking about minimal important differences, but that one seems a little bit low.

Adam: 19:38
Yeah, and as a clinician, if I saw someone whose blood pressure only went down by three points, I wouldn't be, you know swayed to change my practice. Really, I probably like, hey, this probably isn't enough, we need to, we need to kind of ramp it up.

Josh: 19:51
Yeah, now, totally Okay. So I think that's the last thing. From method's perspective. 

Look, the thing is we don't do this for money. This is pro bono and, quite honestly, the mother ships kind of eeks it out every month or so. Right, so we do this because we care about this, we think it's important, we think that integrating evidence based medicine and integrative medicine is essential and there just aren't other resources out there. The moment we find something that does it better, we'll probably drop it. We're busy folks, but right now this is what's out there. Unfortunately, that's it. And so we're going to keep on fighting that good fight. And if you believe in that, if you believe in intellectual honesty and the profession and integrative medicine and being an integrative provider and bringing that into the integrative space, please help us, and you can help us by becoming a member on Dr Journal Club. If you're in need of continuing education credits, take our Nancy Acke approved courses. We have ethics courses, pharmacy courses, general courses, interactions on social media, listen to the podcast, rate our podcast, tell your friends. These are all ways that you can sort of help support the cause. So let's jump into the results. So the results are kind of voluminous, it is. They went through a lot, a lot of studies. One of the things I really liked about this paper was you know we ran into this with the Saturated Fat Umbrella Review. It's really hard to describe, like just the volume of data that you are reviewing in a way that the narrative like survives for the reader. You know of your actual paper. Yeah.

Adam: 21:36
And it's almost not like analysis, paralysis by analysis. You just have so much that you're not really sure where to look. Now I think the good thing is they do pretty clearly lay out the data in their figures, yes, and so if you are interested in like, oh, how does vitamin C impact blood pressure, you can just kind of scroll down and find it. So they did organize it well. I just I got kind of lost in the text and honestly had to stop reading it and I just said, all right, let me just go look at the figures.

Josh: 22:10
Yeah, I thought they did a good job with the figures and they have a lot of supplementary data, which is what you need to do here. But I did think, like going through the discussion and even the written part, yeah, I also started skimming and just looking at the figures, like some stuff is just easier. But what I would say is, if you're, we'll post the link for this study, but table one, like it's just like there are like cheat sheets, I think, for clinicians here. Let me see, actually not table one, if you start on, is it figure two? They start just listing out all the different studies, all the different types of interventions, the different diets, the. The effect size is just really clear. It's so nice, right? They tell you immediately how many you know millimeters of of mercury change, what's the quality of the study, what's the quality of the evidence. It's all in one picture, it's all in one figure and I just freaking loved that and I thought that was just so for clinicians. Cheat sheet, you know, figure one's going to walk you through all of the randomized controlled trial data for systolic blood pressure. They've got a similar one for diastolic, similar one for observational, and I just thought that was a great way to present this data, and so, before we jump in on that one, though, I did want to highlight one other thing. Sort of a theme that popped out at me was the quality. So this is just nuts to me, and this has been shown in multiple nutrition studies already, but I never believe it. And then it's like sitting again and again. People don't realize how crummy nutrition research is, and this just drives that home. So they look I mean, this is a massive review of nutrition systematic reviews, and looking at the quality tool, amstar two, which is the fully accepted, you know, quality assessment tool for systematic reviews, only seven and a half percent had high quality from a methods perspective. In other words, like you could put faith in the systematic review. You're reading only seven and a half percent of the time Right, and 92 plus percent of the systematic reviews out there are like low quality, critically low, like it was just, like you know, very surprising to people that don't know the nutrition literature, but this is like this has been shown time and time again. There's a researcher out of Texas which is showing that the same thing with their nutrition research as well. Like, across the board, the evident that the quality of the studies and nutrition systematic reviews in general, but also the primary literature, are just appalling. So that's number one I thought was interesting. The other terrifying thing okay, well, josh, maybe that's just the systematic reviews. No one knows how to do systematic reviews. What about, like, the quality behind all these diets and all these bad things that are in the news all this time? It's even worse. So looking at NutrGrade, which is a way it's sort of like grade, but for nutrition studies there are some differences we probably don't have to get into they found that only 4.1% of the meta-analyses of randomized controlled trials, which of course would have the highest level stuff, were rated as having a high NutrGrade score 4.1%. So basically, eat whatever you want. Yeah. So talk about evidence, nihilism, right? It's like the evidence behind all this stuff is garbage and the research evaluating the evidence behind all this garbage stuff is also garbage. So, anyway, just like mind-shockingly crazy, there's so much research out there, 175 systematic reviews they're going through and the vast that, like over 90% of this stuff is like, is garbage. So, with that being said, let's focus on the non-garbage. We're going to talk about the non-garbage now, which will make our conversations a lot briefer. If you're interested in more, then I would say go to all these tables, go to the supplementary stuff. You can literally look up your favorite micronutrient, your favorite vitamin, etc. And see what the overall effect is and what the quality of the evidence is. But just to talk about the best evidence, so just the pattern from a pattern perspective. Very low carbohydrate, aka ketogenic diets, versus low-fast diets that was high quality evidence for that, or high quality reviews for that? No, high quality evidence for that. Dash diet, flaxseed, potassium diets, high in potassium, probiotics, grape in its products I thought that was interesting. Nitrates and Stevia, glycoside Is that like stevia? Is that what that is? Mm-hmm.

Adam: 27:09
Mm-hmm.

Josh: 27:09
Okay, and that's, that's stevia. So I just thought that was. That was interesting. So that's where we have high quality evidence for that, for those interventions, and everything else is moderate, low or very low. So where do you want to go from here?

Adam: 27:25
So I did like how they had that table, because as a clinician if you're like, oh you know, if someone wants to do something, you just without even looking at the data you can just kind of say, see, okay, is this going to decrease, increase or just have no effect, and sort of like. In the ND world we always hear about like licorice causing a blood pressure increase, and then you can kind of see here that when you look at herbs, bison, condiments, there is moderate quality of evidence suggesting that licorice actually has no effect on systolic blood pressure and it does increase the diastolic blood pressure.

Josh: 28:02
Where are you? What table are you?

Adam: 28:04
That's on table one. If you scroll down to the neutral grade of moderate and then you kind of go down to where it says yes, herb, spice and condiment, and then look to the right, there is licorice. Right, there Got you. And so you can see that it increases the diastolic blood pressure, has no effect on the systolic blood pressure, and then if you actually want to see quantitatively what that effect is, you can then scroll down and actually look for that in the forest plot. Yeah, this is which is what I'm actually trying to look for right now.

Josh: 28:45
This is fun. Let's pick a few favorites and kind of like talk about this. So I'm looking to looking for licorice, licorice.

Adam: 28:54
Okay, so here it is. It's actually on figure six Figures. Okay, figure six, on the bottom of figure six, when you look at licorice, first controls, there were 590 subjects that were studied. It looks like and if you were concerned about it increasing the diastolic blood pressure, it increased it by 1.74 millimeters of mercury and that ranged from 0.84 to 2.62. So not even clinically meaningful increase in licorice or increase in your blood pressure. Okay, so that's interesting. In your diastolic blood pressure, okay, yeah, and remember, the diastolic blood pressure was the one that was considered to have an effect. There was the systolic blood pressure was considered to have no effect.

Josh: 29:45
That's right. So if you look at figure six A on the systolic, it crosses the line of no effect. And then to your point diastolic I'm just catching up with you here. It is a statistically significant effect of increasing, but, like you said, 1.74 does not cross that minimal important change. And then the Okay, so this is cool. So okay, so everyone is freaking out about licorice and actually when we look at the data on, it doesn't seem to affect systolic, does increase diastolic, but not by much that would be considered clinically meaningful. And you say, well, josh, maybe that's just because it's low level evidence and really it's terrible. But actually when we look very clearly at figure six B I love these figures you can quickly see that the quality of the evidence was moderate, which is pretty darn good. Right, it's just one level blow high. And then the quality of the systematic review evaluating it, telling us it was moderate, was moderate as well. Not bad either. So we've got decent evidence suggesting that this increases diastolic, but not to a meaningful degree. What a useful figure Like. In a few moments you can look this stuff up and fact check all this crazy stuff that everyone's talking about. So this is great. What are your other favorite things to think about from a blood pressure perspective.

Adam: 31:03
Well, one that I always you want to go straight to is the dash diet. There's high level of evidence for it. It's recommended all the time. When you actually look at, like the American College of Cardiology, like guidelines within their guidelines, my understanding is that they have an estimate of it reducing your systolic blood pressure by around 10 or 11 millimeters of mercury. But when we look at this that seems high, which is high, yeah, which is a lot, which is actually very clinically meaningful. But then when we look at this paper, even though there's high evidence for it to improve systolic blood pressure, based on this paper, when the study that they included apparently had just over five and a half thousand participants and it only reduced the systolic blood pressure by 3.2 millimeters of mercury in that range from 2.3 to 4.2, which seems really quite low and not consistent with what the American College of Cardiology has suggested.

Josh: 32:07
Well, so this is interesting because it says the quality of the evidence is high. But look at, the quality of the systematic review is low. And I was curious about this because there must be I don't know 20 systematic reviews on the dash diet, right, and they picked the one according to their criteria that had the most data. But clearly that wasn't a very good systematic review. It's ranked as low and so I wonder if maybe they're missing important studies. Maybe the ranking of high for the evidence level is not done well, like it isn't done properly. So this is a good. This is a great example of when I saw that in the method session I was like I wonder how that's going to play out and we don't have any discussion or comparison about. Well, of all the 10 systematic reviews, the high quality reviews say X, versus just the ones with the most data. So that's interesting, good point. But on its face it meets that three parts, three millimeters of mercury, minimal, important difference, which we say is a little bit suspect too. Okay, that's great, great example. What else should we look up?

Adam: 33:14
I do think that when you're interpreting this, there's a lot of sort of precautions that you do have to take when you're when you're interpreting it, like we just kind of did right there, where you're having all of these different sort of comparisons that you can look at and you pay attention to like, okay, breakfast skipping versus breakfast, there's only 69 subjects in that in that study. So you know you would have to take that with a grain of salt pun not intended there the dietary intervention versus controls. They don't really identify what dietary interventions are. So you would have to go to that gay 2016 article to kind of understand what the definition of dietary interventions is, because on that paper there's just shy of 24,000 subjects with a clinically and statistically significantly meaningful reduction in systolic blood pressure, with a moderate Amstar and moderate Nutrigrade rating. So you know that would be something that would be of interest, but I just think it kind of in general, one thing that that unfortunately is is kind of disappointing is that all of these interventions seem to really have just really small effect sizes and when we look at like a dietary carbohydrate intervention Bueno 2013, very low carbohydrate ketogenic diet versus a low fat diet with just under 1300 participants that was rated high by both Nutrigrade and Amstar, on average only reduced blood pressure by just shy of 1.5 millimeters of mercury. And so, yeah, I mean just, it's just. These effect sizes are so small and they're so small and like almost.

Josh: 35:00
Yeah, you really have to ask. If they matter, it's just almost, you know yeah, you have to ask if they matter. And well, let's talk about effect sizes. So you know, I think this breakfast one that was I highlighted that one too. I think we did a Dr Journal Club video on that one that when one of those papers came out, because I remember getting all excited about like skipping breakfast is so awesome but and it has the largest effect size here of dropping at six. But to your point, the reason it's so high is it's only on 69 people. It's essentially a tiny, tiny systematic review and so your, your, your confidence interval is extremely wide. So it could be the you know the best estimate of six but it could be is actually increase your blood pressure. For all we know, it crosses that line of no effect. And then you look at the quality of the evidence very low and the quality of the of the systematic review critically low. So, yeah, that's a great example where you know it's both. You have to look at a bunch of things. You have to look at the effect size, but also that has to be tempered by the quality of the evidence and that needs to be tempered by the quality of the systematic review to all really important data points, all presented in cheat sheet fashion, in these great, wonderful figures. I just, I absolutely love it. Yeah, all right.

Josh: 36:17
What else should we talk about?

Adam: 36:19
What did that stood out that was actually pretty interesting was that pomegranate juice lowered the, the systolic blood pressure, by basically five millimeters of mercury, and that range from from two to eight. The neutral grade on that was moderate, but the am star was critically low. So I mean that would be something that would just be, you know, interesting to just kind of look at.

Josh: 36:43
Yeah, and I and I just had a thought right now and it wasn't clear to me from the methods, but I think they must have done De novo neutral grade assessments, because most people don't use neutral grade and it would be unlikely, of course, that all these systematic reviews would have used neutral grade and impossible actually and so it must have been that they themselves, the authors, whom I'm very impressed with, based on this study, did a de novo neutral grade assessment of those systematic reviews. They didn't rely upon what those review authors said was the quality of the evidence, and that is actually quite useful, I think, because if that's true, then when we were talking about, like dashed diverse control even though the am star rating on that systematic review is low, we can be confident that that systematic review at least had the most data. And then these apparently excellent researchers then went in and said well, let's look at the quality of the evidence based on the most data, and it is high. So actually that's kind of good. I kind of like that. If that's the correct understanding, that gives me a little bit more confidence here.

Adam: 37:49
Yeah, I mean, I think I think that this is a good sort of like desk reference to have as a starting point of like if it comes in. Yes, yeah, yeah yeah, ask me about like, oh, if I, if I did this, how would that affect my blood pressure? Well, you know, you could kind of quickly reference this and kind of look for it, that's right. But it's also really easy to get get super lost in the weeds in this one, yeah, I think. I think really it's one that's a good sort of like reference, to kind of have like a bird's eye view on a question. But I still think that the main takeaway, like as you're kind of going through the data, is that kind of healthier dietary pattern patterns to note to no surprise seem to improve your blood pressure and sort of these less quote unquote healthy dietary patterns seem to to trend towards an increase in blood pressure.

Josh: 38:47
Yep, yeah, I think that's fair. I don't think there was anything earth shattering from this that I saw, with the exception to your point, which is that the effect sizes were pretty small, and I don't know how this stacks up with conventional medications. Maybe you do. Do you have a sense of what the average effect size is of some of the standard blood pressure medications? Is in this ballpark?

Adam: 39:12
My understanding is that on in some past systematic reviews that I have read, it seems that about six is the standard there. Okay, but whether or not that's just from starting doses, max doses, etc. Etc. My understanding is that the average sort of blood pressure reduction, if there's no sort of titration of a medication to a specific target, is about six.

Josh: 39:40
Interesting. Okay, I'm curious, so it'd be neat to stack some of this stuff up against, you know, alternative medications, and of course it doesn't have to be one or the other. The presumption, I guess but that may not be a fair presumption is that it's somewhat additive, I guess, which would be interesting. The discussion did a good job, I think, going through a potential mechanism of action for some of this, for some of the interventions that seem to work, which I thought was interesting. Yeah, I'm pretty sure you glossed over that and rolled your. I'm pretty sure I could. I could see you rolling your eyes across these United States as I was reading through that section. But, yeah, interesting, interesting stuff I would, I would agree. And one thing last thing I'd say on this, because I don't think there's a lot more to say is one of the real values of evidence synthesis work is to be able to map evidence and make the job of the reader and the clinician and the researcher easier. And honestly, I can't think about a better example of these tables where it is just mapped out so clearly, like all the essential data and, again, just super useful. My hats off to them. Like not getting lost in the weeds but presenting all the weeds if people want to look them up, and like that really is the purpose of evidence synthesis. So I don't know any of these researchers but I am like very impressed. So hats off to you guys and gals. Really nice work. I will be putting this on my desktop Desktop reference. I think it's amazing. It's up to date. So, yeah, so we'll see Any last minute things that you wanted to add. Oh, I did. I am curious about vegetarian diets because lately I'm I have delusions of becoming a vegetarian Again. Let me see so, vegetarian versus omnivore. We have 870 participants, 15 studies, statistically significant improvement in systolic two and a half points and so not not cleanly clinically meaningful moderate level evidence, but critically low systematic review Interesting. Okay. So nothing too earth shattering there, but that's about in line with some of the other stuff we're seeing, coolio, anything else you want to add Adam?

Adam: 41:59
No, sir, that's it.

Josh: 42:01
All right. Well, thank you for listening. Dear listener, that was a lot of fun, very useful paper. I have now almost ready to start my slide deck for the NAPCP and awesome. We'll see you next week. Take care, everyone. 

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Hey y'all. This is Josh. You know we talked about some really interesting stuff today. I think one of the things we're going to do that's relevant. There is a course we have on Dr Journal Club called the EBM boot camp. That's really meant for clinicians to sort of help them understand how to critically evaluate the literature, et cetera, et cetera.Some of the things that we've been talking about today. Go ahead and check out the show notes link. We're going to link to it directly. I think it might be of interest. Don't forget to follow us on social and interact with us on social media at Dr Journal Club DR Journal Club on Twitter, we're on Facebook, we're on LinkedIn, et cetera, et cetera. So please reach out to us. We always love to talk to our fans and our listeners. If you have any specific questions you'd like to ask us about research, evidence, being a clinician, et cetera, don't hesitate to ask. And then, of course, if you have any topics that you'd like us to cover on the pod, please let us know as well. Welcome to Learn More.