You’re probably reading this because you heard that calcium supplements may increase the risk of a heart attack. Because of this let's review the evidence and give you some information to help.
What Kind of Calcium Study Was This?
The study people are talking about was published in the British Medical Journal. This investigation was actually a compilation of previous studies on calcium and looked at heart attacks and other outcomes from 11 different calcium clinical trials, which all totaled included, 12,000 people. In each study, people received more than 500 mg of calcium a day.
These facts are important because the results may not hold true for those who take less than 500 mg of calcium a day. All studies used calcium only.
In other words, none of these were calcium and vitamin D studies.
Also, this study did not directly investigate calcium and heart attacks. Instead, the researchers asked those who did previous calcium studies about their observed side effects. This is important to remember.
Do Calcium Supplements Cause Heart Attacks?
The study found that calcium supplements resulted in a 31% increased chance of a heart attack compared to those who did not take calcium supplements. Calcium was also associated with a non-significant increased risk for stroke and overall death. Non-significant means it wasn't “statistically significant.” It doesn't mean you shouldn't pay attention to it because it's definitely “significant” if it happens 
The risk of a heart attacks seemed to be greatest when people already were getting over 800 mg of calcium from their foods. This was seen in both men and women.
This study is actually a follow-up to another investigation published in 2008 in the British Medical Journal which also found more heart attacks in those who took calcium supplements. This other study involved 1471 older women (average age 74) who were followed for 5 years.
What Type Of Calcium Causes Heart Attacks?
This study noted that it didn’t seem to matter which type of calcium (calcium carbonate, calcium citrate, etc) people took. All types appeared to increase heart attacks.
Do Calcium Foods Cause Heart Attacks?
No. This study does not show that calcium from food causes heart attacks. On the contrary, several studies show that calcium eaten from food seems to decrease
How Do Calcium Supplements Cause Heart Attacks?
While this study did not offer any explanation of how calcium supplements might increase heart attacks, one theory put forth was that calcium increases the hardness (calcification) of blood vessels in a similar way as it increases the hardness of bones. Regardless of theories, more research needs to be done before scientists know how calcium supplements might do this.
My Thoughts About This Study
Let me try to offer some help as you grapple with all of this stuff:
- Everybody is different so talk to your doctor before you stop taking your calcium supplements
- This study found more heart attacks in people already getting over 800 mg daily from food. If you eat a calcium-rich diet now, try to figure out how much you're getting from food. If you believe you need more, try increasing calcium from food before adding a calcium supplement. Food calcium has never been shown to cause heart attacks.
- Most who take calcium supplements don’t know that the best research on the bone-building effects of calcium comes from looking at people who get their calcium from foods. In other words, calcium supplements don’t seem to be as good at building bones as calcium-rich foods.
Craig, as a personal trainer, I agree. I personally work out at a higher intensity with fewer repetitions (8-12) and sets. I encourage my clients to do the same, with proper safety precautions.
I just heard another discussion of the calcium supplement controversy on NPR today. I currently take 1,000 mg. per day with magnesium and trace amounts of boron, as well as Vitamin D3, but starting to rethink the amount of calcium. As far as milk is concerned, I think that is a personal preference. I tend to drink more almond and soy milk but still have organic yogurt, eggs, whey protein, and BGH-free cheese in moderation.
However, I am concerned about calcium absorption in the presence of vegetables with oxalic acid, such as spinach and beets. Joe, have you seen any studies on this?
Craig, sure. When I see women lifting weights in the gym as a way to battle osteoporosis, they often use a resistance that is way too light (5 lb for example). I see women lifting for 15 reps or even sometimes 20 reps.
While this will do some good in the beginning, after the first several months, the bones will need a greater resistance to grow stronger and harder, something on the order of 6-8 or 10RM. I believe the ACSM recommends 50% of 1RM or 70% of 3RM which are pretty heavy.
I was a little vague in the post because I didn’t want a women who was beginner to start lifting very heavy weights before their bodies (ligaments, tendons etc) had the time needed properly adapt to exercise. Progressing too fast would increase the rate and risk of injuries.
When I work with someone who has osteoporosis I don’t specifically think about making the bones stronger for at least the first 3 months of consistent strength training.
Joe, you said “The problem is that most women who lift weights do it the wrong way”. Can you elaborate?
Dena, you said “Unfortunately, most of our food is processed, especially milk products”. Can you elaborate? The milk I drink is pasteurised, nothing else. I’d hardly call that processed.
I highly recommend reading Dr. Know’s posts on this topic. There are two…
http://www.knowguff.com/2011/04/do-calcium-supplements-cause-heart.html
http://www.knowguff.com/2011/04/warfarin-vitamin-k-and-calcium.html
These seem to be the most educated and enlightening discussions on the topic I’ve read…and I’ve read quite a bit since the study was published.
Judy, I agree that there will probably be some disagreement among doctors about the new vitamin D recommendations. Run it by your doctor and see what she thinks. She knows your health history best and can give you better advice than just the those recommendations.
Joe-I do remember reading it now. I had my Vitamin D levels checked over a year ago, when I was taking 800-1,000 IU daily, and while they were in the normal range with supplementation, they still weren’t that high. In speaking with my doctor, she mentioned they were a little on the low side, so I probably would not reduce my intake in the winter months. I think after hearing the IOM report on NPR about the potential harm of taking too much Vitamin D, I became concerned, but it is evident that not all physicians share this view. http://www.npr.org/2010/11/29/131668100/medical-panel-don-t-go-overboard-on-vitamin-d
Hi Judy. the new IOM vitamin D recommendation is for people 70 and younger to get 600 IUs per day. This is up from what it used to be – 400 IUs. I think what we may be seeing is scientists taking a conservative approach by looking at all the research as opposed to individual studies that report amazing outcomes. We have all heard about all the good vitamin D can do but there is also a another side where too much vitamin D may reduce bone strength and maybe promote some types of cancer. I’m guessing these new vitamin D recommendations are supposed to take into account both of these outcomes.
Regardless of what the recommendation is I think its best if people have their vitamin D levels checked by their doctor first so they can get an idea of how much might be best for them.
Here is something I wrote about vitamin D in case you missed it http://supplementclarity.com/vitamin-d-facts/
What do you think about the new IOM recommendations for Vitamin D? I still believe more than 600 IU are necessary for most people, especially during the shorter days.
Hi Mary. I have never heard of any study showing the calcium supplements reduced memory. Have you spoken to your doctor or pharmacist or dietitian about this? That is what I would recommend. if you find an answer I hope you comment again so everyone can learn from your experiences.
Hello,
I came upon this site serendipitously while looking for an article describing the effects of calcium supplements and memory. I ask this because eight months ago I took calcium supplements (with D, magnesium and zinc) along with B12 supplement, and noticed my memory power decreasing slightly. I attributed it to the B12 and ceased that. Then, a few weeks later I discontinued my calcium supplements without any reason. Over the next five months or so I didn’t notice any deficiency in my memory power and forgot about the problems I had encountered. Now I have been placed back on calcium supplements for prevention of osteoporosis and have once again noticed my memory getting fuzzier. All this to ask if you have any information about calcium supplements causing memory fuzziness?
Ashlegh. Thanks for your comments. you make some good points and I like the emphasis on calcium from foods because that is where the research is strongest. A lot of people do use calcium only though -think about Tums. Its always being marketed as a calcium supplement. Hopefully you are lifting weights too for your bones. Many women unfortunately dont lift weights correctly when it comes to offsetting bone loss.
A calcium supplement worth taking is only one that is combined with D3 and Magnesium. Mine has zinc, also… Otherwise, if it’s just straight calcium and nothing else, it does no good anyway, as it won’t be absorbed properly, so who takes that kind? No-one! So it’s a bit of a bogus “study” to claim that Calcium supplementation causes heart attacks, and then not even bother to explain why or how that happens… I notice the age was 74 for most in the study that followed them for 5 years (age 79) — maybe that age group had something to do with the heart attacks, too… If that were so patently true that calcium supplements cause heart attacks, then why do doctors recommend 1200 mgs daily via supplementation? I’ll still take my 666 mg (333 per tablet; I take 2 per day)… With the other 534 mgs of Calcium the doctor says I need, to try and come from fresh foods like fat-free cottage cheese, low-fat ricotta cheese, fresh spinach, and other fresh leafy greens and fresh veggies, and melons, and organic milk, and low-sugar yogurt…
Judy. I also would like to see what happens when the 3 are taken together. I would even settle for more vitamin D + calcium research on heart disease. As hyped as this study was on TV etc, it only asked researchers about the bad stuff that happened to people enrolled in previous studies. While I am leaning toward thinking there maybe something going on, this fact is a big problem that does give me pause.
I take calcium with Vitamin D, as well as magnesium, which decreases blood pressure, if that makes a difference. It would be interesting to see the results of research on these 3 substances taken together. My doctor recommended 1500 mg. of calcium per day, not that I take that much, but I agree with Dena that it is tough to obtain sufficient amounts from food. Not everyone can get adequate food sources on a daily basis. As someone with a strong family history of osteoporosis and decreases in bone density already, I am more concerned with the risk of fracture, and I do weight train, but I cannot make up for not doing so in my 20’s, when bone loss begins.
Hi Dena. The news media may have taken the study out of context. I read the study and the authors do say that we do not know what would happen if calcium is combined with vitamin D. This is a limitation to the study that didn’t get a lot of attention. I mentioned this fact in my review.
Apparently, the study about calcium was taken entirely out of context. Taking calcium WITH Vitamin D does NOT cause heart problems. And calcium taken without vitamin D is not effective at preventing osteoporosis.
Dena. I drink organic milk which tastes better. I also eat fruits/veggies. More than that I lift weights which acts synergistically with calcium. Can you show me a peer reviewed study published in a nutrition journal that calcium in milk is not bio- available? Also no studies show calcium from food causes heart attacks. Studies do seem to show calcium supplements may.
Of course it’s best to get all of our vitamins and minerals from foods. Unfortunately, most of our food is processed, especially milk products. The calcium in milk products is simply not bioavailable. On the other hand, the calcium in almonds, sesame, broccoli and other PROCESSED foods is not. How do YOU get your daily calcium, Joe?
Dena. Regardless of what Professor Edelstein says, the research on the bone building effects of calcium is strongest when you look at people eat calcium foods -NOT supplements. If food calcium really was less bioavailable, then why do we see stronger bones in people who eat calcium foods. The effect is not as great in people who take calcium supplements. I say food first supplements second because we were designed to absorb food best.
Food first, supplements second. Except that it’s almost impossible to get all your calcium from food. You would need to eat about a kilo of calcium a day! According to Professor Shmuel Edelstein, International Osteoporosis expert and developer of the osteoporosis drug Alpha D3, most of the calcium in milk products is simply not bioavailable because of the lousy ratio between calcium and phosphorus in them! That leaves us with some green leafy vegetables, almonds and sesame. I think the calorie content in nuts sort of precludes getting 1200 milligrams a day of calcium from them!!!