Leah:

Hello and welcome to the Ideal Nutrition Podcast. I am Leah Higl and I’m here with my co-host Ada Muir and today we’re gonna be talking about creatine and kidney function. So in the fitness world, we do see a lot of concern regarding creatine and kidney function. Since creatine is filtered through the kidneys, this can also result in kind of abnormal kidney function results on a blood test, which is definitely something we’re going to unpack during this episode.

But a lot of people do avoid creatine for this reason, or are told by medical professionals to stop taking creatine or to avoid it. So again, we’re gonna unpack it all and kind of come to a general conclusion on this one.

Aidan:

So starting off with the mechanism, creatine breaks down to creatinine and that then gets excreted by the kidneys. Creatinine levels are often used as a marker of kidney function just in general. This is because creatinine levels building up in the blood is often a sign that the kidneys are not functioning effectively. But obviously this gets skewed if we are taking creatine which breaks down to creatinine.

Leah:

Yeah, so whilst normally this creatinine is a marker of kidney function, it is often kind of falsely elevated by consuming creatine because you know the creatine breaks down to creatinine so it’s kind of this elevated amount of creatinine in the actual blood. So whilst it is an elevated level it is kind of not really a great way to look at kidney function because it’s kind of being falsely elevated. And in general like the safety of creatine in people with healthy kidneys is it is really safe. So we have decades of research on creatine and long-term outcomes and we know that this is not a problematic issue.

Aidan:

So let’s talk about that research. The main study I want to point to, it’s a relatively old study but I’ll explain why I’ve gone to this one. It was titled long-term oral creatine supplementation does not impair renal function in healthy athletes. And it explored basically all the research that there was at that time and found it clearly does not increase the rate of decline in kidney function which is what we would care about. If creatine was bad for kidney function, we would see declining rates over time, right? I am generally hesitant to reference studies that are that old. And you can find that in the show notes if you want to look at it, but creatine has been studied for so long and new research has not given any reason to change this belief about the safety of creatine. We have an abundance of evidence showing that for people with healthy kidneys are the baseline. It’s just not an issue.

Leah:

Is there just one issue with kind of having these elevated creatinine levels? Is it could mask actual issues with kidney function that may be declining kidney function over time for other reasons outside of having kind of creatine on top of that. So if it was going to have like elevated creatinine levels regardless, it’s like, well, we could just brush this off as being, it’s just the creatine instead of, there’s actually kind of a decline in kidney function.

So I definitely see value in either dropping the creatine supplementation for a period of time and then retesting kidney function. And then if all the levels have normalised, we can go, all right, it was just the creatine. It was just falsely elevated for that period of time. I can now kind of safely continue taking creatine ongoing and that’s not gonna be an issue.

The second recommendation we could have here is testing something called cystatin C which is also a way to test kidney function or EGFR, which again is kind of our general kidney function. So we can have a look at cystatin C as a marker of overall kidney function and that is not going to be falsely elevated or changed by creatine supplementation. So it’s like, if we had these elevated creatinine levels, we could just kind of chuck this on a blood test and go, all right, we’re going to check this as well. And if that’s normal, then we can kind of continue supplementation because we know it’s a false elevation.

Aidan:

And it’s worth just being aware of that anyway, just because people who have a lot of muscle mass and or who train hard in general anyway, can have blood tests coming back showing increased creatinine levels, even if they’re not taking creatine anyway. So it’s good to have this is sad and see thing as another backup as well.

Now, a bit of an obvious question that should come up in relation to the fact that I very clearly stated with healthy kidneys to the baseline is what about people who do not have healthy kidneys to the baseline? What about those who have lower kidney function? I obviously understand more caution with this. The logic simply would be that because the kidneys are struggling to filter out waste in general, because they have lower function, it doesn’t make sense to add more to that burden. That’s the logic. In the show notes, we’ve added a bunch of studies looking at this and they range from looking at older adults with CKD through to people who’ve recently undergone transplants and none have identified issues.

And one little underrated thing that I do want to talk about for a second is that most older people have declined kidney function. A lot of people over the age of 60, like the majority of people would be classified as stage three chronic kidney disease. And that’s so worth being aware of whenever you look at research looking at higher protein intakes in people over a certain age and or creatine supplementation in people over an age, they actually already fit into this category. Stage three, typically not an issue for stuff like this. I would understand caution with somebody very, very, very progressed chronic kidney disease or acute kidney injury as well.

But then you’d also question it’s like, well, is creatine supplementation your priority? that’s like, it’s not like you’re out there smashing weights and stuff like that. Like if you’re in that acute kind of phase, but going just one step removed from that very, very far progressed area, from what we’ve got, it seems pretty safe. It’s another area where people say more research is needed and I would agree, but it has also been studied for decades with no issues so far. So that’s also something to be aware of. I’d be aware, I’d understand caution is what I would say, but I haven’t seen anything that convinced me that in many cases it’s an issue.

Leah:

As a little bit of a summary, we can kind of say that creatine in general is super safe, which is why it is so commonly recommended to people in the kind of the sports and athletic space. We know that its safety levels are really, really high. But as Aidan said, caution should be taken if there is already declining kidney function or very low kidney function. More research would be nice here. We don’t know exactly what the outcomes would be. So a little caution on that one. But if you are someone who is concerned about this, who has good kidney function overall, but has that elevated creatinine level, just get that cystatin C checked and make sure that that’s all good and golden. And then you can go from there in regards to your supplementation. But overall, creatine is safe for those with healthy kidneys.

Aidan:

This has been episode 171. As always, if you haven’t left a rating or review, we’d massively appreciate that. We actually had a massive spike in downloads after the last time I put on my story just asking for ratings and reviews. It generally means so much. Like we had a massive jump in the podcast charts. We actually got it up to top three in Australia for the nutrition thing. Like ratings and reviews, like the podcast charts are massively skewed based on these things. They matter so much. So if you haven’t already, we would massively appreciate one.