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Calcium supplements and heart attacks: More data, more questions

Why take a drug, herb or any other supplement? It’s usually because we believe the substance will do something desirable, and that we’re doing more good than harm. To be truly rational we’d carefully evaluate the expected risks and benefits, estimate the overall odds of a good outcome, and then make a decision that would weigh these factors against any costs (if relevant) to make a conclusion about value for money. But having the best available information at the time we make a decision can still mean decisions turn out to be bad ones: It can be that all relevant data isn’t made available, or it can be that new, unexpected information emerges later to change our evaluation. (Donald Rumsfeld might call them “known unknowns.”)

As unknowns become knowns, risk and benefit perspectives change. Clinical trials give a hint, but don’t tell the full safety and efficacy story. Over time, and with wider use, the true risk-benefit perspective becomes more clear, especially when large databases can be used to study effects in large populations. Epidemiology can be a powerful tool for finding unexpected consequences of treatments. But epidemiologic studies can also frustrate because they rarely determine causal relationships. That’s why I’ve been following the evolving evidence about calcium supplements with interest. Calcium supplements are taken by almost 1 in 5 women, second only to multivitamins as the most popular supplement. When you look at all supplements that contain calcium, a remarkable 43% of the (U.S.) population consumes a supplement with calcium as an ingredient. As a single-ingredient supplement, calcium is almost always taken for bone health, based on continued public health messages that our dietary intake is likely insufficient, putting women (rarely men) at risk of osteoporosis and subsequent fractures. This messaging is backed by a number of studies that have concluded that calcium supplements can reduce bone loss and the risk of fractures. Calcium has an impressive health halo, and supplement marketers and pharmaceutical companies have responded. There are pills, liquids, and even tasty chewy caramel squares embedded with calcium. It’s also fortified in foods like orange juice. Supplements are often taken as “insurance” against perceived or real dietary shortfalls, and it’s easy and convenient to take a calcium supplement daily, often driven by the perception that more is better. Few may think that there is any risk to calcium supplements. But there are now multiple safety signals that these products do have risks. And that’s cause for concern.

Calcium is a critically important mineral for body function. It’s not only the major building block in bones, it’s required for muscle contraction, blood clotting, and multiple hormone and neurotransmitter actions. Vitamin D function is closely linked with dietary calcium absorption and its activity in the body, and also facilitates the exchange of calcium to and from bone “stores”. The dietary importance of both vitamin D and calcium have been acknowledged and recommended daily intakes have been established for both agents.

Calcium and vitamin D have been studied extensively because the burden of illness from osteoporosis is so great. Almost 50% of all women over the age of 50 will have an osteoporosis-related fracture. And fracture can mean significant, sometimes permanent decreases in quality of life, increasing the odds of ending up in a long-term care facility, and raising mortality risks dramatically.

About two years ago I asked if calcium supplements were causing heart attacks. New studies were raising questions about efficacy and safety, which was worrying. Some older data had pointed to the potential relationship. In 2010 Bolland et al. published a meta-analysis of all randomized controlled trials of calcium supplements (≥500 mg/day), excluding trials that also gave vitamin D concurrently. Two sets of data were analyzed: those with patient-level data, and those with trial-level data. Both data sets, when analyzed, showed an association of calcium supplement consumption with increased rates of heart attacks — the relative risk increase was about 30%. There was some fair criticism of the analysis after it was published — the studies were never designed or intended to assess cardiovascular events as primary endpoints; a composite endpoint was not significant; and the exclusion of studies of calcium given with vitamin D made the value questionable, given treatment is now typically with both products. Bolland subsequently addressed the vitamin D question with the (161,000 patient) Women’s Health Initiative dataset, and added in two other trials that studied calcium and vitamin D. Once again, he observed a significant increase in heart attacks. Finally he combined all the data into one overall risk estimate: calcium alone, and calcium with vitamin D. The association was still present and statistically significant: A 24% relative risk increase for heart attacks in those that take calcium supplements.

In light of the warning signals, I suggested two years ago that caution be exercised with calcium supplements, and that routine supplementation in the absence of a dietary deficiency was inadvisable. Furthermore, given no harms had been shown with dietary intake, that all possible efforts should be made to maximize intake by that route. Finally, I suggested that in the case of dietary deficiency, that the potential risks of therapy be considered, along with the expected benefits. Given the modest benefit of calcium supplementation on real outcomes, like fracture risks, the cardiovascular warning signals were concerning enough that they should factor into treatment decision-making.

That was 2011. There’s new data and new guidance on calcium supplements. And the risk and benefit perspectives have shifted again.

In 2012 Li and colleagues examined a group of Heidelberg, Germany residents enrolled in the publicly-funded European Prospective Investigation into Cancer and Nutrition study. Like Bolland, the goal was to evaluate the relationship between dietary calcium, calcium supplements, and cardiovascular events like heart attacks and strokes. Participants were asked if they took vitamins and supplements regularly — dosages were not recorded. Over 23,000 patients were examined for an average duration of 11 years, and 354 heart attacks, 254 strokes, and 267 cardiovascular-related deaths were reported by participants and confirmed by examining medical records. A long list of potential confounders were adjusted for, including total dietary calcium intake, consumption of anti-inflammatory drugs, and reported high cholesterol levels, in order to isolate the potential association of supplements with any cardiovascular benefits.

There were significant differences between the groups, which complicates the interpretation. Consuming higher levels of dietary calcium was associated with a number of other factors including younger age, more education, more physical activity, less smoking and less alcohol consumption. Supplement users were more likely to be women, more active, and less likely to be overweight. However there was more smoking and less education in this group. Controlling for these factors, the authors observed the following:

  • Dietary calcium intake did not appear to affect the risk of cardiovascular disease. When consumption was divided into four groups by total intake, the third quartile had fewer cardiovascular events than the lowest quartile. The risk for stroke was increased in the second quartile for two years, then disappeared. Overall, there was no clear pattern observed.
  • Calcium supplement consumptionwas associated with more heart attacks, but not strokes or overall cardiovascular death. The observed rise in heart attack risk was substantial and statistically significant (hazard ratio of 1.86, confidence interval of 1.17-2.96). This elevated risk was even higher in calcium-only supplementers, where a 2.39x elevated risk was observed (confidence intervals 1.12-5.12).

There were a number of important limitations to the conclusions, a notable one being that calcium supplement doses were not collected. However, the large population, long duration of study, and confirmation of all outcomes, like heart attacks and deaths, supports the credibility of the analysis. The lack of association between dietary calcium (dairy and non-dairy) and cardiovascular death is reassuring. On the other hand, the relationship between calcium supplements and heart attack risk is consistent with the Bolland meta-analyses, and troubling. We now have different authors studying a different dataset and identifying the same signal,which strengthen the hypothesis that this association is real.

Next we have an analysis by Xiao and associates. The study, Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality was published in JAMA Internal Medicine in February 2013. It also used a massive cohort of patients, pulling data on almost 400,000 adults enrolled in the NIH-AARP Diet and Health Study. This study started in the mid-1990′s and assessed dietary and supplemental calcium intake over 12 years of follow-up. Calcium supplements were taken by about a quarter of all men and over half of all women. Again, there were differences between calcium supplement users from non-users: They were more likely to be non-Hispanic whites, to have more education, to be active, to rate their health as “excellent”, and to eat more fruits, vegetables and whole grains. Supplement users were less likely to smoke and consumed less alcohol.

They found the following:

  • Calcium intake as supplements (>1000mg/day) by men was associated with a 20% elevated risk of cardiovascular death, due to an increased incidence of heart disease (confidence intervals 1.05-1.36). There was no effect on rates of stroke.
  • Supplemental calcium intake by women was not associated with cardiovascular death. There was a slight but non-significant increase in supplement users compared with nonusers.
  • There was no relationship of dietary calcium intake to cardiovascular death in men or women.

Once again, the lack of any association between dietary calcium intake and cardiovascular disease adds strength to the findings in other studies. Some reassurance, but more questions. The association with cardiovascular death in men only, but not women, is puzzling. Is the association real? My personal sense is that the association identified by Bolland looks more real than it did two years ago, despite the Xiao findings. So while we don’t have consistent evidence of harm, we do see an association that probably should not be ignored.

So what’s the role of calcium supplements? If it comes down to an evaluation of risk and benefit, where does calcium supplementation fit?

Two days ago the Vitamin D and Calcium Supplementation to Prevent Fractures in Adults: U.S. Preventive Services Task Force Recommendation Statement was published. As should be clear from the name, the USPSTF makes recommendations about prevention — not treatment. It does not consider cost, but only benefit and harms. This was an analysis that looked at primary prevention — the supplementation for adults (community dwelling, not hospitalized) for bone health in the absence of confirmed osteoporosis or a vitamin D deficiency. It did not look at the appropriate dietary intake levels, or the effects of calcium supplements alone. It also did not consider outcomes unrelated to bone health such as prevention of falls, cardiovascular disease, or overall mortality. Consequently, the data set studied by the USPSTF excluded the studies discussed above. With respect to cardiovascular outcomes, it remarks that the association of harms is “not consistently demonstrated”.

The new statement reflects the findings of two systematic reviews and a meta-analysis which sough to understand the relationship between vitamin D, calcium, bone outcomes like fractures, and adverse effects of taking supplements.

With respect to the net benefits of supplements, it made the following observation:

Except for postmenopausal women, there is inadequate evidence to estimate the benefits of vitamin D or calcium supplementation to prevent fractures in noninstitutionalized adults. Due to the lack of effect on fracture incidence and the increased incidence of nephrolithiasis in the intervention group of the WHI trial, the USPSTF concludes with moderate certainty that daily supplementation with 400 IU of vitamin D3 and 1000 mg of calcium has no net benefit for the primary prevention of fractures in noninstitutionalized, postmenopausal women. Although women enrolled in WHI were predominately white, the lower risk for fractures in nonwhite women makes it very unlikely that a benefit would exist in this population.

The final recommendations summarized as follows:

  • insufficient evidence to determine benefit of calcium & vitamin D supplements in premenopausal women or in men to prevent fractures
  • insufficient evidence to determine benefit of calcium (>1000 mg/day) and vitamin D (>400 IU/day) in postmenopausal women
  • sufficient evidence to recommend against supplementation with calcium (<1000mg/day) and vitamin D (1000mg of calcium and >400IU of vitamin D) in postmenopausal women and older men.

It’s also nicely summarized in this handy table:

USPTF image

It also calls for prospective trials to study the benefits of vitamin D and calcium supplementation in early adulthood on fracture incidence later in life. Quite frankly, we’ll be waiting decades for this — if it ever appears.

Conclusion

Assuming benefit from a drug or supplement, in the absence of confirming evidence, can lead to bad health care decision-making. Yet we do this all the time, particularly with supplements that are generally believed to be safe and effective. These studies show that supplements can indeed be rigorously studied, and that surprising findings can emerge. Not only have calcium supplements been closely scrutinized for therapeutic use in dozens of prospective clinical trials, the evidence suggests that use in the absence of deficiency is at best, probably useless, and at worst, substantially elevating the risk of heart attacks and cardiovascular death. Without any clearly established benefits for most people, but exhibiting worrying signs of harms, it’s time to take the health halo off calcium supplements.

References

Li K., Kaaks R., Linseisen J. & Rohrmann S. (2012). Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg), Heart, 98 (12) 920-925. DOI:

Xiao Q. Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality: The National Institutes of Health–AARP Diet and Health StudyCalcium Intake and CVD Mortality, JAMA Internal Medicine, 1. DOI:

Moyer V. (2013). Vitamin D and Calcium Supplementation to Prevent Fractures in Adults: U.S. Preventive Services Task Force Recommendation Statement, Ann Intern Med, DOI: 10.7326/0003-4819-158-9-201305070-00603

Posted in: Herbs & Supplements, Nutrition

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30 thoughts on “Calcium supplements and heart attacks: More data, more questions

  1. windriven says:

    “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.

  2. DugganSC says:

    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.

  3. Janet says:

    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. :-)

  4. windriven says:

    @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.

  5. Calli Arcale says:

    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. :-P

    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.

  6. Robb says:

    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

  7. DugganSC says:

    @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?

  8. Angora Rabbit says:

    @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.

  9. WilliamLawrenceUtridge says:

    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?

  10. stanmrak says:

    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.

  11. Scott says:

    @ stanmrak:

    OK then, where are the PMIDs demonstrating that vitamin K + calcium is better?

    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.

    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?

  12. elburto says:

    @windriven -

    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

    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

    It may not be a question of sufficient calcium, but rather, insufficient Vitamin K.

    [citation needed]

    Also[ ...] cultures with the highest calcium intake have the highest rates of osteoporosis

    [citation needed]

    many cultures with little or no calcium intake have very low rates of osteoporosis

    And for the hat-trick-

    [citation needed]

  13. WilliamLawrenceUtridge says:

    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.

    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.

    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.

    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.

  14. windriven says:

    @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.

  15. mousethatroared says:

    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.

  16. WilliamLawrenceUtridge says:

    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.

  17. Angora Rabbit says:

    “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. :)

  18. WilliamLawrenceUtridge says:

    @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.

  19. RUN says:

    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?

  20. pharmavixen says:

    If calcium supplementation results in transient rises in plasma Ca that can result in intravascular calcification, perhaps sustained-release dosage forms are warranted.

  21. egstra says:

    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.”

  22. annappaa says:

    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. :)

  23. Alia says:

    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.

  24. egstra says:

    “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

  25. Nema Tode says:

    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?

  26. Purenoiz says:

    @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

  27. Reading Frame says:

    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

  28. marilynmann says:

    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.

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