Feb 28 2013
Calcium supplements and heart attacks: More data, more questions
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“Calcium supplement consumption was associated with more heart attacks, but not strokes or overall cardiovascular death. ”
More MIs but no change in cardiovascular death? These MIs are just postcards from Captain Karma warning people to ease off the Ca supplements?
Supplemental calcium comes in different forms (e.g. carbonate, citrate, etc.). Any differences in morbidity data?
An ounce of cheese has ~200mg of calcium, a glass of milk ~300mg. Reaching the RDA of 1000mg from nutritional sources doesn’t seem at all difficult.
Hmm… I wonder whether the calcium supplementation in other foods, such as orange juice, is safe, or if it’s the same as taking calcium pills.
There’s a part of me that also wonders whether the common source for most calcium supplements, cuttlefish bones, may be the factor that’s being missed here for why supplements are that much more dangerous than dietary calcium.
I used to take calcium–around the time of menopause, but gave up all supplements in my journey to skepticism, a process which included my weight loss and general health improvement. I don’t do much dairy for caloric reasons, and get my calcium from mostly from leafy greens, cheese as a garnish only, and plain non-fat yogurt (which is dairy, I know, but I use it sparingly).
I’ve come to realize that old people don’t really need to eat much at all to be perfectly healthy!
It’s good to see the data, which support my current stance of no supplements without good evidence of benefit. Of course, the caveat is that one needs to eat a balanced diet–not much calcium in Cheetoes, alas.
@Duggan
I didn’t know that cuttlefish bone was the source for supplementary calcium. Thanks. Cuttlefish bone is primarily calcium carbonate. Calcium occurs in milk as a phosphate. It would be interesting to learn if there is a significant difference in the way the body metabolizes the two.
Not all calcium supplements come from cuttlefish bone. For instance, Tums (which is primarily sold as an antacid but is also widely used as a calcium supplement) gets it from limestone. Which is sort of the same thing, plus a few hundred million years. Their website says they do not use animal byproducts except in their sugar free products, but I guess the compressed shells of fossil invertebrates don’t count.
I have used Tums as a supplement; when I’ve given platelets, that’s what they had me chew to counteract the calcium depletion due to the anticoagulant binding to calcium in my blood. And I’ve used it *lots* as an antacid. I have acid reflux disease. I’m on omeprazole now. I remember reading about a study done before the invention of H2 inhibitors like cimetidine, looking for a way of treating erosive esophagitis due to acid reflux. In the study, people were given large amounts of oral calcium carbonate for I think a couple of weeks. These were people with really severe acid reflux. They found that in most of the patients, it worked, allowing the damage to heal — but people had to drop out of the study because it was causing heart attacks due to hypercalcemia, and I think there was even a death. So the study found that the treatment worked, but should only be done in extreme cases. I don’t remember the details, but I remember the bit about an increased risk of death due to heart attacks. So not only is this not surprising to me, it isn’t new knowledge either. The increase in heart attacks should be *expected* from indiscriminate calcium supplementation, IMHO.
What is the suspected mechanism by which calcium would lead to increased cardiovascular health issues? Does it contribute to arterial plaque? Is calcium supplementation outcompeting magnesium absorption? If it is due to calcium contributing to arterial plaque, does that suggest too much is being consumed and not enough being deposited in bone properly? Is vitamin D, or lack thereof, a factor in that? According to a quick stats search, osteoporosis is expected to continue to rise unabated, despite decades of calcium supplementation so there must be more to the problem than a simplistic “more calcium = less osteoporosis”.
http://www.iofbonehealth.org/facts-statistics#category-23
@Calli:
I stand corrected. All of the pill varieties of Calcium I’ve seen have a warning saying that the product is derived from shellfish and may trigger such allergies. I’d forgotten about Tums, although it too uses Calcium Carbonate. Apparently, juices use Calcium Citrate Malate, which is more water-soluble, but is less calcium dense. I wonder whether the studies accounted for different sorts of supplements.
Incidentally, the link above does mention the 2010 study, but also notes that the data seems to suggest that people who were already taking supplements didn’t show the increased risk, but rather people who had not taken Calcium supplements and had recently started with the suggestion being that it’s the sudden change in Calcium levels that causes the issue, not the supplement itself. Maybe that partially explains the results from food where one’s calcium consumption is generally spread out over the course of the day instead of two pills daily?
@windriven: Connie Weaver at Purdue (a leading expert on Ca bioavailability) tells me that most of the calcium supplement forms have similar bioavailability. There are modest percentage differences, with citrate being higher and the carbonates phosphates being a little lower. Her recommendation was that it didn’t really matter; take what makes you comfortable. You would want to take the carbonate form with meals since the acid helps solubility but can compete with iron intake. The citrate form can be taken anytime.
I would like say about this topic, because I think there are some important caveats to raise, but sadly it is the case of writing grant vs. commenting on someone else’s blog. I am deeply concerned that the USPMTF recommendation will be misinterpreted. I hope I can make time to read it and track what my Ca VD colleagues are saying.
What I will point out is that 1000 mg/d supplement may put a person in excess of the AI, which is 1200 mg/d for both males and females >50 yrs. UL is 2500mg/d. Since mean Ca intake for women 60+ is 660 mg/d and men 60+ 797 mg/d (1999-2000 NHANES), this population group is at risk for Ca deficiency. Scott is right in pointing out that a 1000 mg/d supplement could put them well over that, so a person needs to find the right intake to balance their needs. Preference is always for Ca-rich foods but not always suitable due to issues such as lactose intolerance. A better practice would be to take a smaller supplement (eg 500 mg) at a lesser frequency (2-3 x week) depending on dietary calcium intake. So I very much take issue with a blanket condemnation of calcium supplements given the low dietary intake in at-risk populations.
I will also add that the point of calcium is not to keep bone strong but to keep blood supersaturated at about 5 mM. When levels drop, calcium is pulled from bone, dietary uptake is increased, and renal losses are retrieved. If intake is less than losses, the necessary calcium is pulled from bone. This is a loss that can take decades. Peak bone mass occurs in the early 30s, so one is then looking at a lifetime thereafter of gradual bone loss. As intake declines with age, osteomalcia risk is going to increase.
I often wonder if the apparent risks of supplementation are due to the unnatural concentration of what are generally rather difuse atoms and molecules (in food anyway). I realize natural isn’t always better, but there’s something to be said for the evolutionary history of the human body. That history simply didn’t include gram-level intakes of most substances in a single swallow.
Is the lack of increased risk for dietary calcium simply due to the fact that it’s spread out over time?
As usual, a critical part of the equation gets totally dropped out. This time, it’s Vitamin K, which is responsible for moving the calcium in your body to where it’s needed, in your bones, and not where it isn’t wanted, namely, your arteries, where it can lead to heart disease.
It may not be a question of sufficient calcium, but rather, insufficient Vitamin K. Of course, none of the studies mentioned incorporated Vitamin K, making them totally worthless for assessing calcium supplements.
Also no mention of the fact that cultures with the highest calcium intake have the highest rates of osteoporosis, and many cultures with little or no calcium intake have very low rates of osteoporosis.
@ stanmrak:
OK then, where are the PMIDs demonstrating that vitamin K + calcium is better?
Leaving aside the fact that this comparison has way too many confounders to mean much, surely that would tend to imply that supplementation is unwise?
@windriven -
Unless your stupid, stubborn body reacts to dairy products as if they were poisons. Ahem. What I wouldn’t give for a chocolate milk.
@stanmrak
[citation needed]
[citation needed]
And for the hat-trick-
[citation needed]
Stan, if research is so easy, why not get off your ass and prove your ideas. If vitamin K is so crucial and the feature that makes it easy for you to take as much calcium as you want without risking cardiac events, it should be trivial to demonstrate in a well-controlled trial. You’re encouraging people to take risks on imperfect information that you pretend is more reliable than it is because you are attempting to justify your personal choices.
If this fact is so important, so crucially overlooked but casually dropped in a comments section of a blog post, then it should be easy to prove. So drop in some references. Take those references and start a clinical trial. Show your work, present the reasons why you believe this. Anyone can make a claim, making a truthful claim is far more difficult than you pretend it is.
Of course you won’t, you’ll drive-by comment and put people’s life at risk with your unfounded certainty. If this were as settled and concrete as you believe, chances are it would be included in the recommendations made by communities of researchers who are genuine experts in their fields. Is your name on that document? Are we to believe that somehow you are smarter than people who spend their professional lives doing nothing but studying this? You may be right, but masturbating in blog comments won’t get your searing insights into the medical literature and mainstream recommendations. So go on, prove it. Or just go.
Cue “wah, we can’t because of BIG PHARMA” in 3…2…1*
*which, of course, ignores the fact that BIG PHARMA would LOVE another vitamin they could package and sell, just like they sell calcium supplements.
Stanmrak needs to read this…
http://www.cracked.com/blog/5-easy-ways-to-spot-b.s.-news-story-internet/
@mouse
stanmrak is the poster boy for why we test for comprehension as well as speed. Clearly, he can read the words. But he is as a blind dog in a meathouse when it comes to finding meaning among the words.
@elburto
Sorry to learn you are lactose intolerant. Nice job on the three-fer with stammerak!
@ WLU
Eloquent as always. But in this case, pearls before swine.
windriven – okay, that was just my really bad attempt to make my completely unrelated link seem relevant. I just posted it because it’s funny and I thought some readers here might get a kick out of it.
The nice thing about stan is, he’s just here to troll once then leave. Makes me wonder why he reads at all. Probably doesn’t, probably just reads the headline and leaves some useless nonsense. But still, you don’t have to play whack-a-mole with a hydra-head comments thread of nonsense, thankfully he just leaves.
“It may not be a question of sufficient calcium, but rather, insufficient Vitamin K. Of course, none of the studies mentioned incorporated Vitamin K, making them totally worthless for assessing calcium supplements. ”
Wow! VK! Which makes calcium binding sites on proteins by carboxylating Glu to make GLA. We nutritionists and bone researchers *never* thought of that. Thanks, Stan! Oh. Wait. We did think of it, and if you bothered to search on PubMed [VK x osteoporosis] you would find a bunch of clinical and animal studies looking at it. Try searching on Neil Binkley as an example. And guess what happened. It didn’t pan out. The clinical intervention trials just didn’t see a big effect. It was so unconvincing that my colleague who is an expert on the topic switched his NIH research on osteoporosis from VK to VD, where the data are much more convincing. Sure, there’s a good “just so” story with VK but when the human studies were run, a good hypothesis wasn’t supported. Which is why this is Science Based Medicine.
Incidentally, Stan, VK does not “move” calcium. It helps make calcium binding sites on proteins, including much of the clotting system, which, if you don’t know, is actually in the arteries (and veins) not the bone. Which is why K is named the anti-Koagulant factor and not the pro-bone factor.
And our physiology / endocrinology of calcium regulation is *not* to keep bone mineralized. That’s a useful side product. The purpose of the endocrinology (PTH, calcitonin, VD) is to maintain serum Ca at 5 mM for normal muscle function and neural firing.
Stan would be so much more interesting if he would pick up a nutrition text and read it.
Sorry for the sarcasm – grant writing makes me crabby.
@Angora Rabbit
Your smackdowns are delicious, I love your comments with or without both snark and sarcasm. Very informative at a very understandable level. You should blog, or write guest posts here
There are few things I like more than a specialist laying out the technical reasons why a pseudoscientists just-so stories are pseudoscientific. Skeptics should use the term “just-so stories” more often. Such a handy and evocative way of framing things.
Thank you Angora! I agree with WLU that it would be great if you had a blog or wrote articles for this site from a nutrition expert perspective. I love when you comment!
I had also heard similar things that Stan had heard about lack of vitamin K playing a role in not only cardiac events, but also kidney problems. Honestly, I can look up research articles, but that is why I have come to a blog like this, to find help with experts interpreting them, so thank you.
This was a quote from an article (for the lay person) written by someone that has her doctorate in nutrition. She also included a variety of research articles to help with supporting this idea. “Vascular calcification, a known cardiovascular risk factor, is another side effect related to the problem of inducing low vitamin K status in patients on anticoagulants and among the population at large. Failure to activate the hormone osteocalcin because of inadequate vitamin K results in failure to move calcium from the bloodstream into bone. Instead, calcium is deposited inappropriately in other tissues, such as blood vessel walls and the kidneys. This results in arteriocalcinosis (an independent risk factor for cardiovascular disease.) It also results in renal calcinosis because increased calcium needs to be excreted.”
My very basic understanding of this process is that we need VD to help with absorbing the Calcium, but we need VK to help with processes to put the calcium in the bone. Like described earlier, the blood likes a calcium balance, so if calcium is starting to increase, the body tries to keep in balance by placing the calcium in other areas…blood vessels and kidney for example.
Angora, I would love your impression of this, and my other question is, some of the studies that looked at vitamin K, was vitamin D also looked at?
If calcium supplementation results in transient rises in plasma Ca that can result in intravascular calcification, perhaps sustained-release dosage forms are warranted.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2683650/
“This study does not support a role for vitamin K supplementation in osteoporosis prevention among healthy, postmenopausal, North American women receiving calcium and vitamin D supplementation.”
Thanks. I’m vegan and have a family history of osteoporosis, so I’ve been taking calcium supplements for years (only 500 mg). I feel like the benefits outweigh the risks, especially since I don’t really have other risk factors for heart attacks, but I admit it’s more of a gut judgment and that I haven’t done a proper risk/benefit analysis. So I’m definitely interested in reading about the emerging evidence. While I lean toward calcium-heavy greens, I haven’t taken the time to track just how much calcium I’m getting through dietary intake; taking a daily supplement (even only a half dose) probably doesn’t help my sense of complacency.
And I wonder about one more thing – tap water as a source of dietary calcium. I come from a place where the tap water is naturally very hard (which makes washing a true nightmare) and rich in minerals, including Ca. And then there was this Finnish (I think) study in the early 2004 which indicated that drinking hard water may reduce the risk of heart attacks.
“tap water as a source of dietary calcium”
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2488164/
Conclusion
Calcium concentration in water varied substantially from different sources in the USA and Canada. Bottled waters presented with concentrations of calcium covering a very large range. Certain tap and bottled waters present with concentrations of calcium sufficient to exhibit a deleterious effect on bisphosphonate treatment. Alternatively, certain waters may be used as a source of calcium that may provide over 40% of the recommended daily intake for calcium.
So…. it depends
I get healthcare from an HMO that is all about using only evidence-supported medicine. They don’t allow their doctors to prescribe medicine that isn’t supported by evidence. They changed their recommendations about mammograms in response to evidence that more-frequent mammograms are more risky than helpful. But they’ve consistently told me to take calcium+D supplements in spite of all the evidence, even though I don’t have any special risk factors. Any guesses about why an HMO like that would still recommend calcium supplements?
@Robb
There is a common misconception about Calcium and magnesium competing for absorption. They have two different pathways to absorption from the intestine. http://physiologyonline.physiology.org/content/23/1/32/F1.expansion
Magnesium is a calcium channel blocker. http://medicine.johnstrogerhospital.org/cru/resources/chf/25_HF25_iseri.pdf
http://asia.elsevierhealth.com/media/us/samplechapters/9781416045748/Guyton%20&%20Hall%20Sample%20Chapter.pdf
Any association between calcium supplementation and high blood pressure?
Also, my mother sees a naturopath as a PCP, and was recently prescribed megadoses of Vitamin D to make up a supposed ‘deficit’. I’m curious if that actually did anything for absorption or if it might have affected her high blood pressure at all.
Thanks in advance!
-RF
[...] you’ll find several recent scientific references questioning it. For example, see this, and this, and this, and this, and this. If you bother to click through and read the articles, you may well [...]
Another study worth looking at:
Michaëlsson K, Melhus H, Warensjö Lemming E, Wolk A, Byberg L. Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study. BMJ. 2013;346:f228.
http://www.bmj.com/content/346/bmj.f228
This study found that high intakes of calcium in women were associated with higher death rates from all causes and cardiovascular disease but not from stroke.
Although the data are not completely consistent, this and other studies were disturbing enough to me that I asked my mother’s doctor to stop her calcium supplement. She gets enough calcium from food anyway.