HSOS #39: Is Your Calcium Supplement Doing More Harm Than Good?

You've been told to take calcium. Your doctor handed you a number — 1,200 milligrams — and sent you out the door. So you grabbed the supplements, checked the box, and figured you were covered. But what if some of that calcium isn't going to your bones at all? What if it's quietly winding up somewhere you absolutely don't want it — like your arteries? In this episode, Kim gets into the real, complicated, still-evolving science around calcium supplementation and why the "just take a pill" approach deserves a second look. She breaks down why food-based calcium and supplement calcium behave very differently in your body, which vitamins are the unsung heroes that actually direct calcium to the right places, and how to build a practical strategy that works — with or without dairy. This is the kind of conversation your doctor probably didn't have time for. Kim's having it anyway.

Let's talk.

Welcome to Her Season of Strength, where women over 40 reclaim their bodies, their energy, and their voices, without apologies. I'm Kim Duffy, registered dietitian, personal trainer, mom, and your biggest hype woman when it comes to aging like you mean it.

This show isn't about chasing skinny or counting wrinkles. It's about building real strength: physical, emotional, and hormonal. Each week, I'll share straight-talking nutrition tips, sustainable fitness strategies, and conversations that help you feel powerful in your skin once again.

Menopause is not an ending, it is only the beginning. This is your season of strength.

What I Cover in This Episode:

• Why calcium is so critical during the menopause transition and what's really happening to your bones after 40
• The surprising research on calcium supplements and cardiovascular risk that most doctors aren't discussing
• Why taking a 1,200 mg calcium supplement all at once may actually be working against you
• The critical difference between how your body handles calcium from food versus from a pill
• Where excess calcium can actually end up in your body — and why that matters for your heart
• The three "calcium traffic directors": Vitamin D, Vitamin K2, and magnesium and what each one does to make sure calcium goes where it belongs
• The best dairy and non-dairy food sources of calcium, including which "healthy" foods are actually terrible for calcium absorption
• Why the leafy green you've been counting on for calcium might be letting you down (hint: it's not kale)
• How to figure out how much calcium you're actually getting from food before you ever reach for a supplement
• A practical, no-overwhelm action plan for getting the calcium your bones need — strategically and safely
• Click here to listen to Episode 36:  "The Silen

Links & resources for this episode:

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Transcript

[00:00:00] Hi there, and welcome to Her Season of Strength, where women over 40 reclaim their bodies, their energy, and their voices, without apologies. I'm Kim Duffy, registered dietitian, personal trainer, mom, and your biggest hype woman. When it comes to aging like you mean it, this show isn't about chasing skinny or counting wrinkles.

[00:00:20] It's about building real strength, physical, emotional, and hormonal. Each week, I'll share straight talking, nutrition tips, sustainable fitness strategies. And conversations that help you feel powerful in your skin. Once again, menopause isn't an ending. It's only the beginning. This is your Season of Strength.

[00:00:39] Hello. Hello, this is Kim Duffy, host of Her Season of Strength. Welcome back and thank you so much for coming and spending a couple minutes with me today. So since I did episode 36 and it was about bone health, I have a lot of people asking me questions and. [00:01:00] I decided to do an episode specifically on calcium because there is a lot of controversy out there of whether or not we should be supplementing with calcium, especially when we've been diagnosed with osteopenia or osteoporosis.

[00:01:18] And so I really wanted to talk about the. The nuances around calcium, especially since, so many women leave their doctor's office and their doctor says. You need to take 1200 milligrams of calcium supplements, right? And then they send them out the door. They don't talk about what kind of calcium they should choose.

[00:01:40] They don't talk about that they should split it up during the day for the best absorption. They don't talk about making sure that they have adequate vitamin D levels or they don't check vitamin D before they're making the recommendations. And they also don't talk about K two. All of these things are super important [00:02:00] when it comes to being able to use that calcium that we're consuming and pull, actually pull it into those bones, which is where we need it most.

[00:02:09] And the next question I have is that when we are supplementing with higher levels of calcium, there's been a lot of research done that actually. Says it's controversial because this calcium could be, the excess calcium could be being deposited elsewhere in our body where we don't necessarily want it.

[00:02:33] So I wanna talk about in today's episode, what you can do right now to make sure you're getting the calcium that your bones need without potentially causing other problems down the road. And like I said, if you haven't listened to episode 36 called The Silent Thief, taking Back Control of Your Bone Health, highly recommend it.

[00:02:51] I will link it in the show notes here so you can go back and listen to it and maybe even listen to it before you listen to this one. But they're gonna be two separate. [00:03:00] I think you'll get a lot of information out of each of them, but consider listening to that one. And if it gives you that full foundation on bone health, osteoporosis and why all this matters so much for us as women over 40.

[00:03:11] So today's episode, I wanna pick up where I left off. I wanna talk about. What is calcium specifically actually doing in our body? Why is it important? I wanna talk a little bit about what current research is saying on calcium supplementation and heart health. Why? Dietary calcium, meaning, the calcium that we're consuming in foods and supplemental calcium, they behave very differently in our bodies.

[00:03:37] I wanna talk about foods, both dairy and non-dairy, that you can get where you need to be. And the unsung hero vitamins that actually help calcium go to the right places. And then lastly, I wanna talk a little about, more of a practical, realistic, action plan that you can actually use to move forward when it comes to using this information.

[00:03:58] So first [00:04:00] of all, why is calcium so por important for women over 40? First of all, women lose. About 1% of their bone mineral density every single year after menopause. About 30% of postmenopausal women in the US and Europe have osteoporosis. And osteoporosis is just the thinning and the weakening, significant weakening of bones with at least 40% of those women developing at least one fracture from it.

[00:04:34] So as women pass through this, menopausal transition, they're gonna lose a shocking 10% of their bone. However, for one in four women, it's even worse, they are fast bone losers so they can they lose bone at a faster, more accelerated rate than the, and than the average woman. And they can lose up to 20% of bone during this window.

[00:04:58] And estrogen. Estrogen [00:05:00] plays a huge part in protecting our bones throughout our lives. So when we see those levels drop dramatically postmenopausal and during, even during perimenopause, we also see that drop in bone density. And right now the RDA for calcium, the recommended daily allowance is 1200 milligrams for women over 50.

[00:05:24] But here's what's get what? What gets interesting. Are we, how much are we getting that through food? Because the median dairy dietary intake in the US for women over 50 or older is usually only around, I would say, 600 to 650 milligrams a day. So barely half of what is recommended. And that gap is what drives women to purchasing these calcium supplements thinking, oh yeah, the doctor told me 1200 milligrams.

[00:05:52] So even if maybe they are consuming 600 a day. They may still be supplementing at 1200 milligrams. So the I what I [00:06:00] want you to ask yourself, is the supplement the right answer or is there a better way? So the research, what does the research actually say about calcium supplementation? And this is the heart of this full episode here.

[00:06:17] I want to, I don't wanna scare anyone about it, but let's discuss. Okay. So calcium supplementation has long been used to promote bone mineral density and strength, and to help prevent osteoporosis, particularly in older adults and postmenopausal women. Now calcium supplementation may help people to meet their calcium needs, especially for, those postmenopausal women whose bodies are producing less estrogen, causing those bones to absorb less calcium.

[00:06:52] And we have increasing calcium loss in the urine. So the science is saying there, there was a [00:07:00] meta-analysis assist done in 2021 and it was of 13 randomized control tiles involving nearly 29,000 participants. And they found that calcium supplements increased the risk of cardiovascular disease by about 15% in healthy post-menopausal women.

[00:07:21] So supplementary calcium intake of about a thousand milligrams per day significantly increased the risk of cardiovascular disease and coronary heart disease. All right. There was another study. It was a meta-analysis that found that 27 to 31% increase in risk of myocardial infarction or heart attack, and a 12 to 20% increase in risk of stroke with calcium supplements.

[00:07:52] Even when they administered vitamin D with the calcium supplements, it didn't lessen those [00:08:00] negative effects. Now they did a 2025 review that was published in the journal current osteoporosis reports, and it concluded that there is now a large body of trial evidence that demonstrates that calcium supplements do not prevent fractures in community dwelling adults and that they commonly produce GI side effects.

[00:08:25] So they give you stomach problems and they can increase the risk of kidney stones. And then finally, one large study of 30, over 36,000 postmenopausal women taking a thousand milligrams of calcium supplements, and they were followed for seven years, reported a 17% increase in kidney stone.

[00:08:49] Now granted you say, oh, wait, do I wanna to risk a fracture versus having a kidney stone? Maybe the risk is higher for the fracture, right? [00:09:00] But the controversy exists because not all of these studies agree. The Woman's Health Initiative, coronary artery calcium study, found that women who received calcium and vitamin D supplementation for seven years had a similar prevalence.

[00:09:17] And quantity of coronary artery calcified plaque. So that's the kind of stuff that will cause the problems like the heart attacks and the strokes as women that were assigned to the placebo, which suggests that moderate supplementation may not affect coronary artery calcification levels in menopausal women.

[00:09:38] So that kind of says the opposite of what some of these other things are saying. And so the honest answer is that their research is mixed. And the conversation among experts it's ongoing. We need more studies, we need to learn more. What we can say is that the idea that calcium supplements are a harmless, automatic bone fix, it's no [00:10:00] longer the consensus.

[00:10:02] So what, where does the real concern come in? And this is the most compelling and the surprising part. Is, if you think of it this way, calcium is like that delivery truck, and it has this specific intended destination, which is your bones, right? But if it doesn't have the right GPS, it doesn't know really where it's going.

[00:10:25] It can end up somewhere that you don't want it, and that's your arteries. So over prolonged periods of high calcium intake. Retained calcium is likely to be deposited in soft tissues and preexisting atherosclerotic plaques. So those are those plaques in the arteries that causes the problem. So what they're saying is if you already have those plaques in your arteries, that calcium can come and stick to it rather than in your bone.

[00:10:57] And high calcium intakes might be [00:11:00] considered a potentially modifiable. Accelerant of atherosclerosis as well as the stiffening of the arteries. So meaning that might be something that we can take away to see if it decreases the plaques in our arteries. Okay, so calcium supplements rapidly increase circulating calcium in your blood.

[00:11:24] Makes sense, right? So we take calcium supplements, they're gonna increase the levels of circulating calcium in our body, and high levels of that circulating calcium has been shown to increase our cardiovascular risk, dietary calcium. So what we're consuming in food, on the other hand, it provides us calcium.

[00:11:45] To, with a slower assimilation, meaning it allows the body to maintain more of that physiological calcium levels. It doesn't cause that spike in our circulating calcium, which can reduce the risk of [00:12:00] cardiovascular disease. So what is the distinction here? Research shows that calcium supplementation, but not dietary calcium in our food.

[00:12:10] Positively correlates with abdominal aorta, calcification in postmenopausal women. So contributing to the plaques and what they're thinking, the kind of the way it, it works for cardiovascular list, sorry, cardiovascular risk. It includes transient hypercalcemia, which leads to hypercoagulability.

[00:12:34] Coagulability, sorry, it's hard to say these as large words. But it's where our blood clots, right? Coagulates and vascular calcification. So plain English, it's taking large dose of calcium supplement can cause a spike in those blood calcium levels. And your body doesn't know where to put it all.

[00:12:53] So some of it ends up in the artery walls and that's a problem. So the biggest thing is that [00:13:00] we don't fully know this is science in motion, right? The bottom line is that food-based calcium does not appear to carry these same risks, which is why the direction of current research strongly points toward doing your best to get calcium from your plate, not a pill, at least as your first strategy.

[00:13:19] And I know that is not always easy, especially if you know you have Diler diet. Di dairy intolerance, right? It causes diarrhea. That's why I was think I had diarrhea in my brain. Dairy intolerance, right? Or if you are allergic to dairy, then you, it takes out a large chunk of those foods that are gonna give you the calcium.

[00:13:40] So now let's talk about the calcium traffic directors, and that's a vitamin DK two, and magnesium. So getting calcium into your body, it's only step one. What happens to it after that is where these three nutrients come in. Vitamin D helps the body to absorb calcium. [00:14:00] So general adult dosing guidelines for Vitamin D three can range from 800 IUs to 2000 IUs daily.

[00:14:07] And I even recommend typically 4,000 IUs in the wintertime, especially if you're living up here in the north. I believe the line is if you take a line across the upper half versus lower half of the United States, the upper half is where we're gonna need. The northern climates where we don't have as much of that sunshine in the winter time, we're gonna need more vitamin D in the winter.

[00:14:29] So you probably, and not to mention, if you get your vitamin D levels checked and they find that you are. Are very low. You may need even higher dosages, but that's something I never recommend more than 4,000 I use, unless you have a lab draw and they show, the doctor recommends that you need, 10,000 a day or 5,000 a day, or 50,000 a week or something like that, right?

[00:14:53] So vitamin D, very important for absorbing calcium Vitamin K two. So [00:15:00] vitamin K two is associated with the inhibition of arterial calcification and arterial stiffening, both of those things for cardiovascular disease, right? So an adequate intake of Vitamin K two has been shown to lower the risk of vascular damage.

[00:15:17] Because I'm not gonna explain it. It activates the matrix, GLA protein, so it's called MGP, that just basically inhibits the deposits of calcium on the walls of blood vessels once activated by K two. That MGP can bind calcium and escort it out of those areas where that the mineral is destructive, right?

[00:15:40] So where it's not supposed to be like arteries and soft tissues. And MGP is the only known potent inhibitor of cardiovascular calcification, and published data shows that people with a higher intake of vitamin K two have about a 50%, [00:16:00] 57% reduction in the risk of dying from cardiovascular disease and as much as 81% reduction in vertebral fractures, so of the spine, food sources of K two. Where are you gonna get it from? You're gonna get it from things like aged cheese, like gutta, gonna get it from egg yolks, from pasture raised hens. You are gonna get it from nato fermented soybeans and grass fed butter. Yes, I know that's not very many food sources of K two, right?

[00:16:29] So I always recommend if you're doing a vitamin D supplement to do a vitamin D three plus K two, but. I wanna as add a little caveat that you should always ask your doctor about that, especially if you are taking any kind of blood thinners. Okay, next, let's talk about magnesium. Because magnesium is one of those vitamins, minerals, that we it's often forgotten, but it is essential for the enzymes that regulate calcium transport.

[00:16:59] So it works [00:17:00] hand in hand with that vitamin D to make sure that calcium actually makes it into your bone tissue. We're gonna find magnesium in dark chocolate and avocado in nuts, seeds, leafy greens. So a lot more foods that you can get that magnesium in. And magnesium is also helpful for sleep at night.

[00:17:21] And recommendations are, even if taking a magnesium glycinate supplement can help promote sleep a little bit better. So the recommendations I believe are for somewhere between 200 and 600 milligrams at bedtime. But the takeaway is if you're supplementing with calcium.

[00:17:36] Make sure that you have adequate vitamin D and K two on board. It's critically important. They're those traffic directors. They're gonna make sure that calcium gets to where it needs to go. But also making sure to have your vitamin D levels checked also, to know exactly what you should be supplementing, how much you should be supplementing, right?

[00:17:57] So the [00:18:00] absorption of calcium from dairy products and fortified foods, it's about 30%. While absorption from certain plants might even be lower than that due to, there's these compounds that form indigestible salt with calcium, so it's gonna decrease the absorption of calcium. Like the absorption of calcium from spinach, it's only about 5%, whereas for milk, it's a lot higher at about 27%.

[00:18:27] So not all plant sources are equal bioavailability. It really does matter. Where can you get it in? Where are you gonna get calcium In dairy, plain non-fat yogurt, it's gonna have almost 500 milligrams for one cup. Plain y, plain low fat yogurt is gonna have about 450 milligrams per cup. One cup of low fat milk's gonna have about 300 milligrams.

[00:18:55] Keifer is gonna have a little over 300 milligrams per cup. [00:19:00] And then cheeses, it's gonna vary widely between cheese to cheese, but cheese is gonna have maybe somewhere between 150 to 250 milligrams per ounce of cheese. So that's gonna be like, a dice, a chunk of cheese, like a dice. Size of a dice.

[00:19:16] So what are some non-dairy sources of calcium? A can of sardines contains about 350 milligrams of calcium. Collar Greens actually combine a substantial 270 milligrams, and it has a low level of those oxalates, which means that the body can absorb it better, more efficiently than, like we were talking about spinach above, right?

[00:19:44] So a co, a cook, a cup of cooked collard greens delivers about, 270 milligrams of calcium. Bok Choy will give you about 190 milligrams per cooked cup, and kale provides [00:20:00] about 180 milligrams. Kale is also low in those oxalates, so your body can actually absorb about 41% of its calcium. If you would have a cup of fortified soy milk, that's gonna give you about 350 milligrams of calcium, which is actually even more than that cup of cow's milk.

[00:20:21] Calcium set tofu has about 250 milligrams per half cup, so check the label. Look for calcium sulfate in the ingredients. White beans are gonna give you about 130 milligrams for a half of a cup. Chia seeds, about 180 milligrams per ounce. And finally, canned salmon with the bones are gonna give you somewhere between 180 to 240 milligrams of calcium per three ounce serving.

[00:20:54] I'll give you a little pro tip on that. Spinach, it's packed with those oxalates that bind the [00:21:00] calcium to and prevent the absorption. So don't you know, don't count on spinach as your calcium source, even though you know it looks impressive on paper. Instead, maybe reach for the kale or the bok choy or the collared greens if you are working to get increase the.

[00:21:16] Calcium, right? I love spinach. Don't get me wrong. I eat spinach every single day. But when it comes to calcium by itself, it's not gonna be a great source. The bottom line from Harvard Health, 500 to 700 milligrams of calcium through diet and 800 to 1000 IUs of vitamin D as a supplement should be adequate to preserve bone density for many women.

[00:21:41] And getting there through food first is always the preferred strategy. So the question is, should you supplement? I want you to this is how I want you to think about it. Ask yourself, how much calcium am I actually getting from food each day? Maybe you track it for a little while, for a week.

[00:21:58] You might actually be surprised. You might [00:22:00] get closer to your goal than you think, or you might find you know that you get in none. If you do decide to supplement, choose calcium citrate over calcium carbonate. Okay, it's gonna be better absorbed and it doesn't require food. Calcium carbonate is cheaper, but it needs stomach acid to actually be absorbed properly.

[00:22:23] Calcium supplements should not be more than 2000 milligrams total per day for adults 51 and older. Okay? And I usually recommend, 500 milligram tabs. And depending on how much you're consuming over the day, but splitting them up, maybe you take 500 milligrams in the morning, maybe you take 500 milligrams later in the day.

[00:22:49] If you're not getting any calcium, but maybe a 500 milligram supplement is enough, maybe that's all you need. Most experts suggest that if you're supplementing less is [00:23:00] more smaller doses, you space 'em out through the day are gonna be better absorbed than one large dose. There was a 2023 research review that does not recommend calcium supplements because they can increase cardiovascular risk.

[00:23:16] But it does suggest getting enough calcium from food sources. And like I said, once again, if you take blood thinners like warfarin, talk to your doctor before adding K two because it can interact and it can decrease the effectiveness of your blood thinners. And that's definitely some a conversation to have with your healthcare provider.

[00:23:39] We started this episode, asking about is calcium supplementation helping your bones or potentially hurting your heart? And the honor ans the honest answer is it's complicated and the science is still evolving. So this is not a scare tactic. I'm not, don't go to your doctor and say.

[00:23:58] Kim Duffy, the dietician, told me [00:24:00] not to take supplements for calcium. And then he's gonna say, what is she? Crazy? But I think it's okay to question your doctors because doctors don't always know a lot about nutrition. Okay? But have a conversation with them. But what we know for certain food-based calcium is safer.

[00:24:19] It's better absorbed in that context of a whole meal, and it comes with a package of other nutrients that your body can actually use. That's the same with all supplements, right? When we're taking these supplements and we, they have taken them out and they are just a single solitary supplement, we are never gonna absorb it, as well as those foods which contain that.

[00:24:43] Nutrient as well as other ones that potentially help it to be absorbed much better in that whole package, that whole food form. So first, prioritize food. Try to build that calcium rich plate using the foods that we discussed, whether it's dairy or [00:25:00] non-dairy. Pick what works for you, for your body, for your lifestyle, what you tolerate.

[00:25:05] And don't forget those co-factors. Don't forget your vitamin D three, your vitamin K two, and your magnesium. Because those are the traffic directors. Remember, without them even good calcium intake might not be doing its best work. So if you supplement, do it strategically. Use supplements just to close that gap, but not as your primary source.

[00:25:27] Choose calcium citrate. Take it in split doses and loop in your doctor. Have a chat with them. Let 'em know what you're doing. And refer back to episode 36 for that full picture on bone health Osteo pros prevention and those lifestyle factors like strength training and protein intake that are gonna work right alongside all of this and sometimes can make an even bigger difference on your bone health than just calcium.

[00:25:55] But before you go, if this episode made you think differently about what's in [00:26:00] your supplement cabinet, I want you to share it with a friend who needs to hear it. And if you haven't already, please hit the follow button on the podcast. So you never miss an episode every week, we're gonna talk, we're gonna have real conversations about, what's actually going on.

[00:26:13] What is important for women over 40. And the more women who have access to this information, the better. And as always, remember, this is about progress over perfection. We're in this for the long haul, and this is your season of strength. Have a fantastic week.