Leah:
Hello and welcome to the Ideal Nutrition Podcast. I’m Leah Higl and I’m here with my co-host Aidan Muir. And today we’ll be answering the question, do calcium supplements increase the risk of cardiovascular disease? Now this is something that I frequently get asked a fair bit by clients when recommending calcium supplements. So we figured it would be good to just do an episode on it, explore it a little bit and see where we land.
Aidan:
So there’s a few reasons or proposed mechanisms as to why it could contribute to this. The main one, I think the easiest one to understand is that elevated calcium levels from supplements might contribute to calcium deposits in blood vessels, which is obviously a factor for heart disease. There’s a bunch of other mechanisms, but I think that one alone seems to be like the main one that is contributing to this. All the other ones can play a small role, but are a little bit more speculative than that one. That’s pretty clear.
Leah:
Yeah, so getting into the evidence, we are fortunate that there is actually a lot of evidence looking at this space or a lot of research that we can look to to come to a conclusion. So instead of going through individual studies, we will go with the most relevant review, which is a 2021 meta analysis of clinical trials that featured 13 double blind randomised control trials and a sample size of over 40,000 people.
So really good review that is quite recent. The finding was that there was actually a small increased risk of cardiovascular disease specifically in healthy post menopausal women. The increase was around 15 percent. So based on this particular group of research we could say that there there may be an increased risk. Yes.
Aidan:
So there have been five similar reviews that have been done over the years with heaps of research and of those five, three of them found a small increased risk and two found no difference. So it’s not really clear cut. One thing I’ll note, and I’m pretty sure it was the one that you just mentioned, Leah, that review kind of pointed out all the flaws of all the other reviews and it’s like, here’s why these ones didn’t find any link. But it’s not clear cut, but I would kind of say that a safe interpretation is that there’s probably a small increased risk.
Leah:
Yeah. So definitely something to think about. I think the other thing that people will point to is like, what about dietary calcium? Like it is just having a high calcium intake through food going to have a similar risk factor. And at this stage, it only appears to be a risk if it is supplemental form.
So from what we’ve seen dietary calcium intake, it doesn’t increase the risk of cardiovascular disease or cardiovascular events. And some of the reasons could be that a) the dosage in a single sitting is often much smaller. So instead of having like massive amounts of calcium in one hit, we’re usually having that spread over the course of the day. We’ve also got other associated nutrients such as like magnesium, phosphorus and vitamin K coming through whole food sources or food sources of calcium that may have the reduced vascular calcification.
So coming from food as opposed to supplements may be different just from that angle. And then we also have the absorption. So the absorption from food might be slower due to integration with other nutrients in food. So it’s again, not just this like lump sum of calcium being deposited. So calcium levels in the blood rise a lot more slowly from food than they do from supplements. So that’s some of the reasons as to why we may not see this just coming from dietary calcium intake.
Aidan:
Yeah, and adding even more context on that. So calcium supplements are typically done in around 1,200 milligrams per day type dosages, often split two times a day, so 600 milligrams in the morning, 600 at night, partly due to absorption reasons in terms of you’re probably not going to absorb that full 1,200 in a single go. If we add more context around food, like a cup of milk might have around 300 milligrams of calcium. So it’s like, it’s pretty rare that you’re getting well into that type of territory. One of the ones that comes to mind is those John West calcium plus.
Leah:
Yeah, that’s what always comes to mind for me.
Aidan:
What are they like a thousand milligrams of calcium like that? Per can, it’s crazy. So they’re super high. They’re one of the few things that gets into this territory. So it’s like one of the few occasions where it’s like, okay, it’s going super high. But even then you’re like, okay, there’s a bit of magnesium in there. There’s a bit of phosphorus in there that could contribute to that other mechanism you talked about. And then there’s the absorption where it’s like, you’ve got to digest the food and everything like that. So it’s still rise a little bit slower than supplementation by itself.
Now going deeper, we’re going to talk about fractures because, since there is a potential risk associated with calcium supplementation it is worth also exploring the benefits. Because what if there was a small increased risk of cardiovascular disease but there was a massive reduction in the risk of fractures? Like sometimes there is a trade-off that can be worth making. Talking through that though the evidence in relation to reducing fractures is weaker than many would expect and being a little bit cautious with my wording here because there’s a lot I want to talk about.
I’ve mentioned on the podcast before that I did do a systematic review in university, literally on calcium and vitamin D supplementation in terms of reducing fractures. That was obviously 2016, it’s 2024 now. It’s not as relevant. Bit of a tangent, but somebody commented on one of my posts the other day about how they did the honors thesis on something and I stalked their LinkedIn and I was like, that was 1990.
Leah:
That was a little while ago now.
Aidan:
Things have changed a little bit since then, like I wouldn’t be. Yeah. Anyway. 1990 is so, so long ago. Yeah. It’s just not, not that relevant anymore. But, um, the bit that I bring up with that kind of thing is obviously I’ve stayed up to date on that research because I’m interested in that research because I spent so long looking at it. It became a little bit of a passion area. So I know a little bit about this topic, so I’m going to talk about it. So a 2017 meta-analysis note that that was after my research project, 2017 meta-analysis covering 33 randomised controlled trials.
Huge sample size, so randomised control trials, placebo control. Note, once you’ve got 33 randomised control trials on something, maybe there is a point that’s like, maybe we don’t need more research. Maybe we’ve got enough. Including more than 50,000 participants over the age of 50. And I know because I’ve done research in this space, the reason why they’ve looked over the age of 50 is because there’s a lot more research on that than if you had a cutoff of like 65. In my research, I also had a cutoff of 50. Even though fractures are far more likely to occur beyond 65 than they would over 50.
But anyway, 50,000 participants over the age of 50 for calcium and vitamin D supplements, and they found no reduction in fracture risk. That is really interesting, particularly when we factor in that there’s a little bit of a risk associated with calcium supplementation. But let’s go deeper. I think it’s really important to go one more layer deeper. The first really important thing is that similarly sized research, looking at the exact same demographic, found a 0.5 to 1.5% increase in bone marrow density. That doesn’t sound outstanding, but I wanna note a few things.
One, in that age group, most people’s bone marrow density is decreasing. Calcium is a single variable in bone marrow density. It’s not the be all and end all, it’s just one of the factors. And addressing this one factor led to a small increase rather than the decrease that you would expect. So that’s kind of cool. The increase in bone marrow density of 0.5 to 1.5% is a positive, but do we really think that that’s going to massively reduce the risk of fractures? Obviously that’s not going to, but if we take this slightly zoomed out multifactorial view, you can say this like, maybe it’s worth addressing calcium and a bunch of other variables, and maybe we’ll get even more than the 1.5% increase in bone marrow density.
And then let’s go one more layer deeper again. Looking at this research, in many cases, they’re not assessing baseline intake of calcium. Some people in these studies have good intakes, some have poor intakes. They’re just getting a group of people over the age of 50. If you did a subgroup analysis of the people who had low baseline calcium intake and you gave them calcium supplements, they’re getting even more benefit. And then the craziest thing that I found when I was doing my research on this was that many people didn’t take their supplements. And if you looked at the conclusion based on what is known as the intention to treat as in the people who are told to take the supplements, it would say that there was no reduction in the risk of fractures.
And then in some cases, if you just did a subgroup analysis on the people who actually took their supplements, there was a small reduction in the risk of fractures. And that’s just because calcium supplementation is a little bit tricky to take. You have to take it morning and night. The second you go do something twice a day, compliance just drops off a cliff versus just doing something once a day. So that is a very broad deep dive of like, the reason I’ve added that nuance is my actual take is, okay, the evidence for calcium supplementation and fractures prevention is pretty weak.
But if you go deep down the rabbit hole and say you’re working with a professional who has recommended calcium supplements for you and they’ve analysed your individual situation, maybe there is a chance that it’s still a good recommendation.
Leah:
Yeah, like they’ve obviously or ideally weighed up the pros and cons and still think it’s going to be overall beneficial.
Aidan:
Yeah, 100%.
Leah:
The other thing we want to just touch on briefly is vitamin K. So we have previously done a podcast talking about vitamin K2 in regards to when it’s supplemented in isolation or alongside vitamin D and has led to reductions in cardiovascular disease risk. The evidence here also isn’t super overwhelmingly positive, but it’s worth being aware of because it could have potential to partially offset the issues presented with calcium supplements. Particularly if you’ve got one of those like classic bone health supplements, it’s calcium, vitamin D and vitamin K, which is pretty common.
Aidan:
Yeah, exactly right. I’m of the opinion at this stage that although you’re right, the evidence is an overwhelmingly positive for vitamin K too. It’s mildly positive for reducing the risk of cardiovascular disease, but it’s also pretty positive for improving bone mineral density, which is also the goal of what we’re trying to do with calcium as well. So it’s like, if you get a little bit of either of those benefit, it makes sense to add them together. And statistically speaking, it seems like most people don’t get enough vitamin K2 in their diet. So in many cases, it could be a worthwhile addition in just one of those supplements that contains calcium and vitamin K2 and potentially vitamin D as well.
Leah:
Yeah, I think what we miss when we talk about just individual supplements or nutrients is that we miss like the potential synergy of combining multiple nutrients.
Aidan:
Yeah. And I know I spoke about this recently on the podcast as well, but this comes back to the whole thing about there’s been a little bit of criticism of vitamin D not being the magical cure-all kind of thing. And it does come back to it. It’s just one thing. Like it’s just one thing. The same thing, how we looked at that calcium thing being 0.5 to 1.5%. That’s actually pretty cool considering all they did was supplement a individual thing. And there’s so many things going on. But now giving a bit of a interpretation of all this. If somebody doesn’t have a good reason to supplement calcium, they probably shouldn’t supplement it.
Even though it is only a small increase in the risk, that’s still an increase. And if you’re not getting a noticeable benefit from it, I would increase your risk for no reason. If a food first approach is an option, it obviously makes sense to explore that first. So I’d only be really exploring this in people where getting enough calcium through food is not going to be feasible or realistic. And the nuanced approach that I was talking about is that in some cases, calcium supplements can still have benefits. It just only makes sense to take them when the benefits would offset the small potential risk.
Leah:
This has been episode 187 of the Ideal Nutrition Podcast. If you haven’t yet left a rating or review, it’s always greatly appreciated for you to do so, but otherwise, thanks for tuning in.