A high calcium diet and calcium supplementation: Is it bad for you?

A high calcium diet and calcium supplementation: Is it bad for you?

An article from Sweden was recently published showing that in a very large group of women, over 60,000 of them, followed for 19 years as part of an also very interesting study of the effectiveness of mammograms, women who get more calcium, in their diet or as supplements, had a higher risk of dying of anything, but especially of heart attacks. It is unclear why this would be true, but there are various theories.

Further, the study showed that this risk was more pronounced if the calcium was taken as supplements, but still present in women who got their calcium from the food they ate. The highest level of risk was in women who got more than 1400 mg of calcium a day, and an intake of 700-1000 mg a day did not particularly increase risk. The women with the lowest average calcium intake were not at any increased risk of death, which was a surprise to the researchers. Information about calcium intake was taken from the subjects’ reports of diet and supplement use, which was further validated by phone interviews of recent food intake. Since most women think that consuming calcium is healthy, I would guess that there was a tendency to overestimate calcium intake, suggesting that real risk may be present with lower calcium intakes than the study states.

This is big news. Or is it? No, it actually isn’t. In 2010 the British Medical Journal published a meta-analysis of studies of calcium supplementation in healthy people and concluded that there was increased cardiovascular death in those given supplements. There had previously been studies showing that calcium supplements in dialysis patients accelerated calcium deposition in blood vessels and increased cardiovascular death.

It has been part of our general medical wisdom for my many years of practice to recommend calcium, as food or pills, to our women patients. I remember several years ago when we began to be aware of the real impact of osteoporotic hip and spinal fractures in our aging population that physicians were encouraged to recommend to our post-menopausal patients that they take 1200-1600 mg a day of calcium. That was very hard to do. A cup of milk contains about 300 mg of elemental calcium, yogurt slightly more, cheese not much at all. Calcium fortified orange juice was about as much as milk. Dark green leafy vegetables contain calcium, but not a whole lot. A cup of collard greens, cooked, contains about 350 mg, but people rarely eat that much cooked greens. I would work through how to get all that calcium in the diet and usually suggest my patient take a chewable calcium pill for every meal they didn’t eat something that was high in calcium. Luckily for my patients, I doubt many of them really did this.

Calcium supplementation seemed the right thing to recommend after estrogen, which is well known to reduce fracture risk, was discredited by the Women’s Health Initiative due to what appeared to be an excess of heart attacks and strokes in treated patients. There were other medications for osteoporosis, but they had side effects and were really only approved for established osteoporosis, which most patients don’t want to wait to get.

But why did we ever recommend calcium supplements at all? Did we have any good evidence that they worked? Sort of, but in retrospect, not really.

It does make sense, when you think about it, that calcium would strengthen bones. Bones are, after all, made mostly of calcium. Over the last 3 decades at least we have studied the effects of calcium supplementation on both bone density and on risk of fracture. We care most about risk of fracture, because bone density is just a test, and is not necessarily indicative of whether a person will break a bone. The most important kinds of fractures as we age are those of the hips and vertebrae. These are the ones that cause disability and death and are associated with the thinning of bones that comes to many of us with age, that is to say osteoporosis. Although some studies early on appeared to show that taking calcium, with or without vitamin D, reduced these important fractures, later analysis of all of the well done studies showed no benefit. There was even a suggestion that higher calcium intake might have been associated with more hip fractures. Many of these studies were done in the most scrupulous way possible, using double blind prospective methodology or correcting for factors that might make patients with higher calcium intake be those who were at higher risk of fracture in the first place.

What about vitamin D? Does this make a difference?  In the Swedish mammography cohort, vitamin D supplementation did not reduce the risk of heart attack or death that was associated with increased calcium intake. In a recent large study out of Finland from 2010, combining calcium and vitamin D had a slight but not statistically significant effect on fracture risk in a group of 65-71 year old women living in northern Finland. Vitamin D itself is the subject of lots of research and although it may be good to supplement it, especially in people with risks for low levels, it is not clear that it reduces the risk of fracture in the majority of post menopausal women.

So what is the bottom line here? It does appear that taking calcium supplements and deliberately pushing high calcium foods increases risk for death and doesn’t save a person from disabling fractures. Doctors have so many things that they need to advise people about in a preventive office visit, getting exercise, quitting smoking, controlling their blood pressure, getting vaccinated against dread diseases. Now we just don’t have to also tell our patients to drink milk and take large and unpalatable calcium pills. We should probably tell them if they are already doing that, to stop the pills and concentrate more on a healthy balanced diet, with plenty of fruit and vegetables and fish and olive oil. We can rejoice in having one less thing to fuss about!

Janice Boughton is a physician who blogs at Why is American health care so expensive?

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  • George Wilson

    Perhaps weight bearing exercises combined with a good diet is a better choice. Just increasing calcium in the diet doesn’t mean the body will automatically place it in the bones. Excess vitamins and minerals are excreted from the body as anyone who has tried energy drinks discovers when they see their bright yellow urine. I think it would be better to stimulate osteoblasts with weight bearing exercises than by trying to create a hypercalcimic environment that could have negative effects elsewhere in the body. Great article. Thanks for raising awareness.

  • MarylandMD

    The big question is why so many physicians were suckered into recommending so much calcium and screening so many patients for vitamin D deficiency based on the weak initial evidence. Sure, it might make sense that more calcium and vitamin D would help, but then again, it might not. Why should you think that megadoses of calcium or vitamin D (a fat-soluble vitamin–you did go to medical school, didn’t you?) would not have a potential downside? It became such a fad. We were suckered by the Folic Acid craze of the early-mid 2000s (remember that?), and instead of learning our lesson, we happily rode the calcium and vitamin D bandwagons. Honestly, if we keep getting fished in by these silly trends, we are acting more and more like a bunch of Dr Oz clones…

    • Guest

      It doesn’t do much for the image of so-called “science-based medicine” when real doctors buy into and then promote these ephemeral alt-health crazes.

      • MarylandMD

        Every lecture I have been to about “evidence-based medicine”, you have some physician stand up and declare: “We have always practiced evidence-based medicine!” I feel like standing up and responding with a big laugh, “No, we don’t, buddy. Really, we don’t.”

  • http://twitter.com/TFontyn Trish Fontyn

    How many of these 60,000 supplemented K2 with the calcium and D? Or maintained alkalinity? With those two factors unaccounted for, this does not tell us anything that was not already known years ago.

    • Dorothygreen

      Because vitamin K2 is not on the researcher’s or physician’s radar.
      Until physician’s recognize the synergy of nutrients and the importance of K2 – directing calcium (that D has helped to be absorbed), into the bones, AND through activation of a protein, keeps calcium out of the arteries – the right questions will not be asked.
      Vitamin K2 and the Calcium Paradox is the book to read and understand vitamins K2, D, and A. and their relationship to one another. Very well researched. Since the last study in Osteoporosis International (I think) I have upped my supplement of MK7 to 180 mcg. Natto is just too difficult to eat.

  • Guest

    “Lots of people are Vitamin D deficient, so many of us that the Australian Government recently queried why testing for Vitamin D has gone through the roof over the last ten years.”

    Is there a correlation to the “slip-slop-slap” campaign and the government-promoted paranoia about any citizen being exposed to any sunlight whatsoever? Yes, sunbaking is bad and it’s wonderful that Australia is taking steps to prevent more melanomas, but SOME sun exposure, maybe 20 minutes while walking to school or to the shops, especially before 9am, is not unreasonable for people to get.

    • elizabeth52

      You’re probably right, it would be having an effect. It’s a campaign that started many years ago now. I stay out of the sun to protect my fair skin that burns so easily and I have a couple of skin issues. (vitilego and dermatitis now and then) I still try to get some sunshine though, obviously not enough, my reading was only 21, so I take supplements.

      There is some interesting research that suggests melanoma is not caused by sun exposure. That turns things on it’s head…also, it’s being over-diagnosed, like breast and prostate cancer.

      “Melanoma Epidemic: A Midsummer Nights Dream” Journal of Dermatology, 2009

  • http://twitter.com/piyoaworld Dennis Lee

    It’s because the pills are never isotonic capable and will burden the digestive system and can’t really dissolve in water!! There is only one of a kind that is water soluble and safe!!! Just scan my QR code to learn about it.

  • Faxon

    Dr Boughton, Please provide the study name, authors, where/ when published! I want to discuss this with my doctor, and ” I read something on the Web” will not do! I have done several google searches with the info you provided and can not find which study you are referring to. Thank you so very much-

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