Leah:

Hello and welcome to the Ideal Nutrition Podcast. I am Leah Higl and I’m here with my co-host Aidan Muir and today’s episode is, how much does sodium affect blood pressure? Obviously the title of this podcast leads with the assumption that salt sodium does in fact affect blood pressure. We’re gonna go into this, but it is a little bit more complex than that. It is a complex topic. So we’ll start by unpacking that first and then get more into the specifics.

Aidan:

So the first part of unpacking that is going straight into like, why would there be any case against reducing sodium intake in relation to the blood pressure stuff? So there’s three main arguments that I see that we will address, but three main arguments that commonly come up in relation to this. I’ve seen a lot of like very smart people in the exercise space have really strong opinions on this topic. And the three explanations I see are typically, the first one is if you don’t have high blood pressure and you are relatively fit and active and healthy, then you probably don’t need to worry about this.

The second argument I see is that there is a thing called sodium -mediated hypertension or sodium sensitivity basically, where only the people who are sensitive to sodium need to worry about this. Then the third one is that there is a J-shaped curve where going too high sodium can cause issues, but also going too low sodium causes issues, so you’ve got to avoid going too low as well. So those are the three main arguments.

Leah:

Okay, addressing the first claim, it is mostly valid. So sodium plays a role in blood pressure, which we will discuss. But if someone doesn’t have any issues with their blood pressure, it’s probably not a concern. If somebody is an athlete who happens to have a very low sodium diet, they may actually benefit from increasing it. In practice, when I’m working with someone who is a healthy, active individual, it’s rare that I’ll be too concerned about their sodium intake. If anything, if they’re quite active, like I said, I might actually look at ways we increase their sodium intake.

A really good example of this is working with some powerlifters who you get really lightheaded during training sessions, deadlifts and things like that, I may actually get them to take salt tablets and things before training or athletes taking electrolyte powders and what not. So it is rare that I will be really kind of honed in on reducing someone’s sodium intake if they fall into the category of not having an issue with blood pressure and otherwise being a healthy individual.

Aidan:

Yeah and every now and then when I talk about something like that, some people will be like, oh, do you have it? Do you have research showing that this makes people perform better in the gym? And like, to be honest, it hasn’t really been much research looking at that. But I have had so many people come up to me and say that that has changed things for them. Like I can name at least 10 people who have listened to a podcast where you have said that. They’re like, oh, I used get lightheaded in the gym. Now I don’t. I’m like, okay, like at some stages, like, do we need a study measuring lightheadedness in the, like, if you tried something yourself in this scenario and you’re like, oh, night and day difference.

Leah:

If it works, it works, right?

Aidan:

Particularly if there’s no downside, because if we’re coming back to the perspective about being like, okay, if you don’t have issues with blood pressure, what would be the downside of doing this? Talking through the next one. So sodium mediated hypertension is a thing that is a legitimate thing, but it gets complex when you look at the stats. It seems like the vast majority of people who have high blood pressure or hypertension, it seems like the vast majority of them have sodium mediated hypertension.

So at a population level, it’s like, okay, well, it makes sense for people with high blood pressure to reduce their sodium intake. But if you’re listening to this and you’re like, hey, I’m not a population level, I’m an individual, you can test this, but it’s logistically challenging. Since you have to test and retest this a lot for a long time to confirm if it’s relevant for you, you’d have to get a blood pressure monitor and just sit there and be like, high sodium intake today, did this matter?

So on and so forth. Then you could also make a little bit of an argument that’s like, what if you had sodium mediated hypertension? Is that dangerous to test and retest that? Is that like a bit of a risk? So you can see why at a broad level, like people are just like, just reduced the sodium intake, but you could also go down the individual route there. If you happen to be interested in looking at that claim a little bit further, we’ve added a paper into the show notes on this sodium mediated hypertension, because it’s a bit of a deep topic, but if you are interested, you can find that in the show notes.

Leah:

On the flip side of that, really low sodium diets also have evidence of contributing to cardiovascular events. So you can go too far in that direction as well. But the dosages are so low that it’s really something that you need to be like really trying to do in order to achieve it. So it’s not usually something that is going to happen just as part of a regular diet, like by accident. So it needs to be kind of well below that 1000 milligram per day amount before it appears to be or have a likelihood of causing issues. So it’s pretty impractical that someone is going to get there without actively trying, but I think it’s something to be aware of as part of this.

Aidan:

So let’s answer the question. Does sodium raise blood pressure on average? And the answer is really nice and yes, it does. It’s not really debatable at a population level. It does raise it at a population level on average. A 2019 review covering the majority of research up until that time concluded that reducing sodium intake not only decrease blood pressure, but on average, it reduces morbidity and mortality coming from cardiovascular disease. That’s pretty compelling. Like that’s a pretty strong claim. And that is the summary of the evidence.

There are a bunch of mechanisms that play a role here. The simplest one for me personally is that sodium draws water into the blood that would obviously increase pressure. But it also does things like increasing arterial stiffness and a few other things. But I think just at a population level, it’s super interesting to just like be like, okay, it increases blood pressure on average at a population level.

Leah:

Yeah. And adding a little bit of context around that. So talking about how much this actually does play a role in increasing blood pressure. There are actually some pretty nice clear numbers that we have from randomised control trials on this. So an RCT that involved reducing intake of sodium from 3,700 milligrams to 2,000 milligrams per day found a reduction in systolic blood pressure by around 7.1 millimeters of mercury on average.

A little more context here is that healthy is often considered 120 millimeters of mercury over 80 millimeters of mercury. So again, adding a little bit context of how much that 7.1 actually is. And then from a sodium intake perspective, lot of the majority of the population appears to be kind of around that 3,500 milligram intake all the way up to 5,500 milligrams of sodium per day. So that particular study is super relevant to the average person who is consuming like around that 3 to 5,000 milligrams of sodium per day. And if they were to reduce it to more that kind of 2000 milligram amount, we would likely see this reduction in blood pressure overall.

Aidan:

Yeah. And this is where it gets complex when communicating just to a large mass of people in general, because you could look at that person that is really smart in the fitness space talking about potentially increasing sodium intake. And you can go to angles that cycle. Hang on. The average person is consuming this amount is putting out a message of having more really helpful. But then you could also be like, are people in the fitness space who are so dedicated to clean eating and they happen to also not add salt to anything who could end up with quite a low sodium intake unintentionally because they’re not really focusing on that.

But I absolutely love numbers like looking at the like that 7.1 units reduction. Like I love numbers like that because it gives context about being like, how much of a difference does this make? Like I think it’s useful, like I would rather hear, okay, this is the kind of difference you can expect versus just being like, this helps with this. It adds a bit of context. But obviously there’s nuance there. We want to unpack a little bit about that. Those are just averages, of course. And then sodium is only one small factor in blood pressure. I believe we have another podcast where we talk about nutrition for reducing blood pressure, but there are so many other variables.

Potassium intake, body weight, activity levels, overall diet, like if we look at stuff like the DASH diet, like from memory, like the original DASH diet study had actually a relatively high sodium intake and they reduced blood pressure significantly. They later redid more research with low sodium intakes and it reduced even more. So it’s like, this is a variable that matters. It’s not the only variable that matters, but it’s good to know how much you can kind of expect with it.

Another complex thing that is really hard to communicate and also go through with research is how much consistency versus inconsistency matters with sodium. going deep into this one, your hormones such as aldosterone influence partly based on how much sodium your body expects to be coming in based on your recent intake. There’s a little bit of a lag effects there. If somebody has a low intake of sodium normally, and then randomly has a high intake, they will experience more water retention than somebody who normally has a high sodium intake all the time.

Because if you had a high sodium intake all the time, your hormones are set up in a way where your body’s trying to excrete sodium a little bit more quickly. This likely plays a role in acute changes in blood pressure too. It’s very complex to try to summarise simply with numbers and stuff like this, but I think it’s also worth being aware of with this consistency versus inconsistency with sodium intake too.

Leah:

To summarise, sodium does play a role in blood pressure on average. That is something that we know. But like Aiden said, it’s not the biggest variable, but it does matter. So it is something that if you’re looking to reduce your blood pressure, potentially this is something that you look at changing or reducing overall. But there is a huge individual variation and that will be the biggest factor in how much this matters on a person to person level.

Some people are so far away from having an issue with high blood pressure due to other variables that this won’t, it’s not something they have to consider. Whilst other people have a really high sodium intake, which may be contributing to their issues with high blood pressure. And in that case, we potentially should look at reducing. So it’s not like we can have this blanket statement for everybody around sodium, but it is a factor to consider in blood pressure issues.

Aidan:

This has been episode 159 of the Ideal Nutrition podcast. If you have not already, if you could please leave a rating and review, we would massively appreciate that. But apart from that, I hope you enjoyed listening to this and hope you learned something in the process as well.