- Is eating too much protein damaging your kidneys? If you search online, you'll find seemingly contradictory evidence to this question. So in this podcast, we're gonna dive in here. We're gonna explain both sides of the argument and whether or not you should be worried about how much protein you're eating. Let's get started. Welcome back team to the Building Life Along Out of These podcast. Thanks so much for stopping by, really appreciate it. For those who don't know me yet, my name is Jordan Wrennke. I'm a dual board certified physician in family and sports medicine. And the goal of this podcast is to keep you active and healthy for life through actionable, evidence informed education. And today we're talking all about high protein diets if they're damaging for your kidney. And you might notice a little difference here on the podcast. What I'm doing now is I'm having the longer podcast. It's gonna be a little more free flowing and it's gonna be more in detail like it kind of been previously. But then each week I'll have a shorter video if you wanna check that out on YouTube, kind of summarizing things. So this will be kind of the in depth one. This is kind of the to feed my nerdy side and to scratch that itch. But it's not gonna be too much different if you listen to it. I just wanna let you know that resource is also available. So what is the problem? Why are people talking about this? Well, high protein diets are everywhere. They're getting increasingly popular but there's lots of concerns about what are they doing to people's kidneys, right? You look around and you see carnivore this, keto that, low carb, all this stuff. And people are eating a lot of protein. I mean, even mainstream now people are starting to say it's so important for our overall health, for muscle mass, lots of things. And so that's why we care about it. And on top of that, we care about damaging your kidneys 'cause if you hurt your kidneys it can lead to something called chronic kidney disease which is a huge problem. It's a major public health issue. It affects millions of people worldwide and can be super, super terrible. If you progress from CKD, there's different stages. If you get to four or five, you need a transplant. You need dialysis, all those things are bad. And so obviously we're not trying to send anybody to dialysis by eating protein. That's our main goal. So that's kind of the big thing. And so that's why here trying to determine the optimal protein intake for performance, being lifelong athletes, all that stuff while keeping our healthiest kidney, our kidneys healthy is crucial. That's really what we're looking for. And so just to take a quick step back, kidneys for most people are familiar at least with the kidneys peripherally, but kidneys are organs in our body and they're largely responsible for filtering waste. That's their big job. They filter waste products from the blood and maintain a healthy balance of fluids and electrolytes in our body. It is incredible when we do nephrology in medical school. My gosh, it's like the most detailed thing in the world. The nephrons, the filtration unit of the kidney and the amount of stuff that happens there is crazy. Absorbing sodium and potassium and water and all this stuff. And there's so much going on. It's incredible that it can do what it does. It's super sensitive to changes. So when we have changes in our blood, it can pull stuff out, it can concentrate the urine, it can dilute the urine, it can absorb stuff. If it doesn't have enough, it can make sure we're doing it. It's just really, really fancy and it can do a lot of things. And a lot of times also our medications specifically for blood pressure, like high blood pressure medications affect and work at the kidney. So lot of stuff going on, super important. And specifically for protein, about 90% of proteins metabolic waste is excreted by the kidney. So most of it coming through there. And a key function when we were breaking down protein, we produce nitrogen. So that's a thing that happens in this kind of nitrogenous waste. It's primarily broken down into the form of urea, another chemical that is filtered through the kidneys and then urinated out. And that's what's happening when we're breaking down protein. We break it down, create excess nitrogen, and that kind of gets formed with urea and then gets excreted out. So a lot of times, if you look at lab tests, we have multiple lab tests to look for kidney function. The big thing we always look at is someone's creatinine level. That's one. Creatinine is kind of a marker of essentially how well your kidneys are filtering. That's one thing. We also have the glomilliary filtration rate or GFR. That is also another proxy. And the GFR is a measure of how well the kidneys are filtering waste products in the blood. And typically we think like higher is better. As you age, that number will start to go down and down and shrink a little bit, but generally the higher, the better. 'Cause if you have a low GFR, that means we're not filtering very much. And that's what we see in later stages of chronic kidney disease. And the GFR is a calculation and it uses that creatine, creatinine like I talked about, and it's a waste product. So a lot of times our muscle, when we have muscle breakdown, that produces creatinine. And so creatinine can also be altered in patients who have lots of muscle, meaning you have like a really elevated creatinine and people see that and they say, "Oh my gosh." 'Cause if you have a really high creatinine and you worry about something called an AKI or acute kidney injury, and somebody who's just really muscled and has a higher baseline creatinine that people get freaked out and sometimes get, referrals or nephrology or stuff. That's a whole nother podcast talking about athletic labs. And we've talked about that in other podcasts as well, but you can get something like a Sistatin-C, which is another way we can measure the filtration that's going on in our kidneys, but it takes kind of the muscle out of it. And so that's one thing to think about. But typically in a lot of the studies we're gonna talk about here, GFR is like the big one that you use creatinine with that typically. And when we talk about like, why do we talk about this? Where does this idea come from that it's bad for them? It's not crazy talk, right? This is not people trying to scare tactic you in a specific diet. There's definitely some mechanistic plausibility behind this as well as literature. And there's multiple reasons what could be going on. You know, one thing first, one postulate that people have is that you can have what's called intraglomerular hypertension and hyperfiltration. So high protein intake can elevate the pressure within the glomeruli, which is the filtering section of the kidney. And this intraglomerular hypertension can lead to hyperfiltration, meaning the kidneys are filtering blood at an accelerated rate. So if you think about your normal rate, it's cranked up when you have a big nitrogen load after you want the protein. And while the kidneys have a functional reserve to handle this, it's not a problem. They can do this temporarily. Prolonged hyperfiltration induced by high protein diets may potentially may stress the kidneys and contribute to damage over time. That's like the general ideas, like why people think this may be problematic. Like, hey, like, hey, can handle this, but you know, we don't want to do it all the time. If it's too long, that's an issue. So that's why people think this might be an issue. And people think sustained hyperfiltration can result in glomerular injury, which then impairs the kidney's ability to filter waste products effectively. And then, you know, once we can't filter things appropriately this can manifest and lead to proteinuria, which we have protein in the urine, which signals kidney dysfunction. And several studies have linked high protein intake, particularly from animal sources to an increased risk of albumuria, which is a specific type of protein in the urine. And that's another reason why people say, "Hey, like we've seen some of this observational studies, we're worried about it, this is there." And on top of that, high protein intakes also lead to a higher production of urea and other nitrogenous waste products, which potentially increases the burden of the kidneys, once again, for excretion, that's what we think about. And then these animal-based proteins as well, in particular, they can also contribute to metabolic acidosis. So a condition where the body's acid-base balance is a little disrupted. And this can be problematic for individuals with CKD, or chronic kidney disease, who already have impaired acid excretion. So if you have chronic kidney disease, you're already not functioning at a hundred percent in terms of your kidney capacity. And then you start to overwhelm it with more nitrogenous waste, more acids, that may lead to an issue. And having your acid-base balance be off, so essentially your body lives in a very, very strict pH and levels, like how acid and how basic it is. And it's very, very, very tightly regulated, a lot of the kidneys do a big role in that. And if you meet too many potentially, potentially acidic things with an already damaged kidney, it may lead to issues, that's what we think about. But if you have this chronic low-level metabolic acidosis, that can be linked to kidney injury and accelerated GFR decline. So that's what we're worried about. On top of that, high protein diets also associated with increased phosphorus intake, and hyperphosphatemia or elevated phosphorus levels is a risk factor for cardiovascular disease and can also contribute to kidney damage. And so that is why people think high protein, specifically high animal-based protein diets could potentially harm the kidney. So mechanistic things are great and observational studies are great. And that's what we see and that's how we base things. And that's where the current understanding is of why this could be an issue. And so I do wanna talk about the source of protein real quick though. The sources of protein, they vary, between animal and plant. And it may, depending on what's eaten and what type of protein you bring in, it may have an impact on kidney health. So specifically, like I mentioned, animal protein, they specifically from red and processed meat, those have been linked to an increased risk of CKD in several observational studies. And once again, potential mechanisms for that include the higher dietary acid load compared to plant protein. Also, other things they say is it may lead to gut microbiome dysbiosis or an abnormal gut microbiome may lead to inflammation, increased phosphate content like we talked about as well. And it is important to note that while these arguments suggest potential mechanisms for how high proteins, specifically how high animal protein diets might affect the kidneys, more researchers needed to kind of establish definitive causal links. It's definitely not there. And many of the studies that I looked at, they were observational in nature, which means we can only show associations and cannot prove anything, right? No causality and the long-term impact of high protein diets in kidney health is still up for debate. And so today I wanna dive into a couple papers specifically here and talk more about what their findings are, they're kind of more recent and bigger studies. So we're gonna talk about, the first is article Chang 2024. And this was a systematic review and meta analysis. This was the first meta analysis to explore the correlation among total protein, plant protein, animal protein intake and CKD risk. So essentially looking at, hey, if you take an animal versus plant versus total, how does it lead to chronic kidney disease or does it all? It included six studies and about 8,700 participants that had CKD in a total of 148,000 cases. So essentially that 148,000 participants in the study in these RCTs looking at it and 8,000 of them had CKD. And the study found a significant association between higher total protein, higher total plant protein and higher animal protein intake and a lower risk of developing chronic kidney disease. So pretty much the opposite of what I was just kind of teasing there in the intro, they found a lower risk there. And overall total protein intake was linked to an 18% reduction in CKD risk. And plant protein intake was associated with a 23% reduction and just specifically down to animal, animal protein intake showed a 14% reduction as well. Notably within the animal protein category, fish and seafood consumption demonstrated a particularly strong link to reduce the CKD risk as well, 16% lower. And they also did notice a dose response relationship, meaning a dose response analysis was done and revealed a nonlinear relationship between plant protein intake and CKD incidence. Meaning they looked at plant protein and consuming 15, 30 or 45 grams of plant protein per day was associated with a 28, 43 and 45% reduction in CKD respectively. So when they mean nonlinear, what they're saying is, hey, as you increase plant protein consumption, we had improvement in reduction of the CKD risk, but it wasn't linear. It wasn't like, hey, I went from 15 to 30 and then we went from 25 to 50, it didn't double like that. It wasn't linear kind of tailed off, but we did see that as we increase plant protein intake, we decreased the risk for chronic kidney disease. And this was a pretty cool study, from a strength perspective, pretty large sample size, over 140,000 people, 8,000 cases of CKD. The analysis they did show that there was a low risk for bias in the studies, which is always good to see as well. And what is it, like, why is this happening? What's the potential explanations for findings? Well, the paper discusses several potential mechanisms that could explain the observations that we saw here between higher protein intake and lower CKD. They're not sure. They thought that potentially for plant protein, plant-based diets can sometimes thought to be less inflammatory than animal-based products. That's not necessarily always true, but we sometimes see that. And plant proteins might exert a lower burden on the kidneys compared to animal proteins. And plant-based foods are rich in dietary fiber, which has been linked to lower CKD as well. But what about animal protein? Well, the beneficial effects observed for animal protein could be attributed to the fact that these, a lot of these studies are done in Japan and Korea, where fish and seafood are the majority dietary components. And red and processed meat consumption, in contrast, has been linked to increased risk of CKD in other studies. Once again, there's no causative thing. They're saying, "Hey, that's definitely it." But they're saying, "Hey, why this animal group? This is not what we expected. Why is it?" They say, "Well, maybe it's 'cause we're in a different group, you know, kind of in Asia, as opposed to just Western studies." But they really didn't have a good explanation for it, but that's one thing they did kind of say, "Hey, it might be happening." And limitation-wise, they're definitely worse than limitations. There are always limitations, right? Despite a comprehensive search, they only killed with six studies. A decent amount of people, but only six studies. And then also the heterogeneity between the different protein types, right? There's lots of variability in results between the different studies, looking at plant protein specifically, suggesting that other factors may be influencing this as well. And then also, they didn't have the most consistent CKD definitions and protein intake measurements. And the included studies use different criteria for defining what CKD was and measuring protein intake, which could potentially, you know, introduce bias and also not be as accurate. But overall, the paper highlights, we definitely need some more future research. It was super exciting, but it was kind of, yeah, I thought it was really cool to look at, and it's something that I didn't expect to see, but pretty big analysis done recently, I thought it was helpful. We're gonna move on to the next article now, and this is by Carbiol in 2024. And this was a multi-cohort study, which explored the relationship between protein intake and all-cause mortality in older adults, comparing those with and without chronic kidney disease. And the research people used data from three main cohorts. They were in Spain and Sweden predominantly. And the study focused on adults age 60 years and older and excluded those with advanced CKD or underlying kidney replacement therapy. So if they're getting dialysis, they've had a kidney transplant or have really advanced CKD, CKD4, they were exempt there. So specifically four and five were excluded. Also on top of that, people undergoing dialysis or kidney transplant, just 'cause that's a very different population than the people walking around in public. So protein was tracked with surveys and food frequency questionnaires, and the study outcome was 10-year all-cause mortality. And so what were the main findings? Well, the higher total protein intake that was seen, higher total protein was associated with lower mortality in participants with CKD. And this association was observed across different levels of protein intake with hazard ratios decreasing as protein intake increased actually. So once again, kind of find similar things where more protein was taken in, the less we saw. And so the adjusted hazard ratios were, when we're comparing one gram per kilogram per day versus 0.8, 0.8 is kind of our baseline, right? That's the recommended dietary allowance, RDA. So when they looked at one versus 0.8, the hazard ratio was 0.88 for 1.2 compared to 0.8, that was 0.79. And for 1.4 grams per kilograms per day versus 0.8, it was 0.73. So as we saw, we kind of increased there. We tended to see a decrease in hazard ratio. It wasn't perfectly linear, meaning that jump from 1.2 to 1.4 didn't increase a whole heck of a lot, but it did show an improvement. So going down to 0.73. So as we see there, we kind of go from 12%, down 21%, down to 27%, increased reduction in risk with mortality when we go up in protein intake. And both animal and plant protein intake were linked with lower mortality in individuals with CKD. And the study found no significant difference in the strength of association between two protein sources and mortality, meaning like animal versus plant-based specifically. And there were associations with mortality. They were, they're comparable once again for plant animal proteins, hazard ratios like 0.8, 0.88, kind of the same thing. And so slightly better with plant protein is what they found, but nothing huge. And the association between protein intake and lower mortality was stronger in patients without CKD compared to those with CKD. So we did see it in both, those who had CKD and those who didn't, both of them got the benefits, but they got even more benefits when they didn't have CKD. And this suggests that while higher protein intake benefits both groups, the benefits might actually be slightly greater for those without CKD. And of note, the study did not find a significant association between the proportion of plant protein in the diet and mortality risk. However, increasing plant protein intake over time was linked to lower mortality, even though increases in total or animal protein were not necessarily. So statistically, stuff didn't really pay out differently, but they saw maybe there's a little trend of plant protein being a little better, but it wasn't like huge. And so what does this mean? Well, these studies findings challenge the traditional recommendation of restricting protein intake in individuals with CKD, particularly those with mild or moderate CKD. The research of the studies propose that the benefits of proteins, such as improved muscle mass, strength, bone health, and immune function, might outweigh the potential risks in older adults with early stage CKD, which is kind of the big thing. There definitely were limitations. The study acknowledged multiple limitations saying, "Hey, the methods used to estimate protein intake varied between cohorts and may have introduced some error." Once again, a lot of food frequency questionnaires and reported self surveys, that can lead to a whole bunch of errors potentially there. And then once again, observational studies can't eliminate lots of confounding factors as well. And then there's also, they wondered how generalizable is this? The majority of the participants in this study consumed a Western diet with high proportion of animal protein. And so therefore the results may not be generalizable to populations following a plant-based or very low protein diet or those with severe CKD. And despite these limitations though, this study provides valuable insights into the relationship between protein intake and mortality in older adults with CKD. And really these findings suggest that moderate protein intake may be beneficial for older adults with mild or moderate CKD. Further research definitely needed, particularly randomized controlled trials are needed to confirm this finding and establish optimal protein intake recommendations for this population, but it's kind of cool. And on top of that, it appears that both animal and plant protein appear to contribute to a lower mortality risk in older adults with CKD. And overall, it seems like a balanced diet with diverse protein sources is likely to be the best and the most beneficial. And overall, I just thought it was kind of cool. We hear this protein is bad for kidneys and based on what we're seeing in the most recent meta-analysis, I'm not as sure about that. And this is not medical advice saying, "Hey, let's go do this." But it seems like tide might be shifting a little bit. It might be changing from, "Hey, you gotta keep a low protein diet" to, "Hey, actually maybe there's lots of benefits to protein that may be beneficial long-term." But that's gonna be it for today. Thanks so much for stopping by. If you did find this information helpful, please take a moment to leave a five star review on your favorite podcast, platform or choice. It really does help other people find this. And that's my goal is to help as many people as possible. And to stay up to date with the latest health news, please sign up for the newsletter, so no miscounts that I email out very rarely. But every once in a while, I email things out just to kind of some updates on things. But that's it for today. Now get off your phone, get outside, and we'll see you next time. Disclaimer, this podcast is for entertainment, education, and informational purposes only. The topics discussed should not solely be used to diagnose, treat or prevent any condition. The information presented here was created with an evidence-based approach, but please keep in mind that science is always changing. And at the time of listing this, there may be some new data that makes this information incomplete or inaccurate. Always seek the advice of your personal physician or qualified healthcare provider for questions regarding any medical condition.
