a large pile of vitamin pills, calcium supplements

Millions of men and women swallow a big calcium pill every day because they have been told it is good for their bones. That advice may be misguided, especially in light of research suggesting that high doses of supplemental calcium could pose risks for the cardiovascular system.

What Is the Evidence on Calcium Supplements?

One study suggesting that calcium supplements might have unexpected risks was published in JAMA Internal Medicine (online, april 22, 2013). Between 1995 and 1996 nearly 400,000 men and women were recruited into the National Institutes of Health-AARP Diet and Health Study. Their calcium intake was assessed with a very thorough questionnaire. They were then followed for 12 years. Men who consumed more than 1500 mg of calcium daily were at increased risk for cardiovascular disease death. The researchers did not find an elevated risk in women who took calcium supplements.

The authors concluded:

“We found a significant interaction by sex. Elevated CVD [cardiovascular disease] mortality with increasing supplemental calcium in-take was observed only in men; however, we cannot rule out the possibility that supplemental calcium intake may be associated with cardiovascular mortality in women.”

Some women took heart from these results, as women seemingly avoided the problem of cardiovascular mortality despite taking calcium supplements. That finding was probably misleading, however.

More Research Shows Women Are Also Vulnerable:

Other research suggests that women may not be immune to this problem. A study in 2012 involving nearly 24,000 German adults found that those taking calcium supplements were more likely to have heart attacks during the 11 years of follow-up (Heart, online May 23, 2012).

The researchers speculated that excess calcium circulating in the body might lead to calcification in blood vessels. Few people realize that the plaque that clogs coronary arteries is made up predominantly of calcium.

Another study involving women only also suggested that large doses of supplemental calcium might lead to heart complications. In this research (BMJ, online, April 19, 2011), more than 16,000 women over the age of 40 were randomized to take both calcium and vitamin D or placebo. Those taking the supplements had about 20 percent more heart attacks and other vascular problems.

A Pattern in the Findings:

Results from 13 other studies of calcium with or without vitamin D were consistent: those taking supplements were slightly more likely than those on placebo to suffer a heart attack or stroke. The researchers estimated that if 1,000 people took calcium for five years, six of them would have a heart attack or stroke and only three fractures would be prevented. Such a risk/benefit ratio is not favorable.

An editorial titled “Calcium Supplements: Bad for the Heart?” in the journal Heart [June, 2012] reviews the medical literature on this controversial topic. Here is the executive summary from the editorial: calcium supplements have been linked to kidney stones, constipation and other more serious digestive complaints, coronary artery calcification, heart attacks and strokes. After considering all the data that has accumulated over the last several years, the authors conclude:

“Thus, the consistent evidence is that calcium supplements do more harm than good and that other interventions are preferable for reducing the risk of osteoporotic fractures…We should return to seeing calcium as an important component of a balanced diet and not as a low-cost panacea to the universal problem of postmenopausal bone loss.”

The Fallacy of Taking Too Much:

Many people figure that if a little calcium is necessary for strong bones (as it is), then a lot would work even better. It is estimated that one of two older men in the U.S. takes a calcium pill and nearly three out of four older women do so. Many health care practitioners have reinforced this attitude and even encouraged older men and women to take around 1500 mg of calcium a day in pill form. The evidence, however, seems to suggest that such large doses of calcium are linked to kidney stones, constipation, coronary artery calcification, heart attacks and strokes (Heart, June, 2012).

In the study published in JAMA Internal Medicine the authors propose a mechanism to explain how too much calcium creates complications:

“One plausible biological mechanism through which calcium may exert a harmful effect on cardiovascular health is vascular calcification–the deposit of calcium phosphate in cardiovascular structures…Emerging evidence has linked calcification of coronary arteries with increased atherosclerotic plaque burden, risk of coronary heart disease and mortality.”

The authors also point out that excess calcium might increase blood coagulation and lead to “stiffness” in the arterial wall.

A more recent study has confirmed that people taking calcium supplements were more likely to have calcification in their coronary arteries (Journal of the American Heart Association, October 11, 2016). In the MESA study (Multi-Ethnic Study of Atherosclerosis), those taking calcium supplements had the highest calcification scores. People getting the most calcium from their diets, however, had the cleanest arteries. You can read more about this study here.

But What About Taking Calcium Supplements for Strong Bones?

Although we have been repeatedly told that calcium supplements will be good for bones, if one really looks at the research, and there is an amazing amount of it, you will discover that the data demonstrating that calcium can be helpful in preventing fractures are exceptionally weak. Over the years more than 140 studies have examined the effects of calcium on fracture risk. About one third suggest benefit. Over half show no reduced risk. The rest were inconclusive.

Let’s take a look at epidemiology. In countries where people consume a LOT of milk, dairy products AND calcium supplements (Scandinavia, the United States and the UK), hip fractures are very common. In countries where milk and dairy consumption is low and calcium pills are rare (Africa, China, New Guinea and Iran), the hip fracture rate is much lower.

What about vitamin D?

Many people believe that if you just add vitamin D to calcium, the problem is solved. The meta-analysis of various studies only analyzed the research that has been completed. Most of the big studies were done with calcium alone. The doses of calcium that were employed in the various studies ranged from 500 mg of calcium carbonate to 1,400 mg of calcium citrate and 2,000 mg of lactogluconate-carbonate.

As for vitamin D, of the nearly 40 studies that have been published involving both calcium and vitamin D combined, roughly half showed fracture reduction and half demonstrated no benefit.

Unless there is a clear benefit from something, we are unwilling to accept a risk. Although the risk of heart attack may seem small in absolute numbers, if tens of millions of women are swallowing large doses of calcium, the number of people who may be vulnerable is actually quite substantial.

We encourage visitors to actually read the BMJ article. It is free and very comprehensive. It is also understandable.

You may also want to listen to our radio show about the pros and cons of calcium supplements with Michael Castleman and Amy Lanou, PhD, authors of Building Bone Vitality and Water Willett, MD, DrPH, Chair of Nutrition at Harvard School of Public Health.

Getting Calcium Without Taking Calcium Supplements

Getting calcium from your diet is not risky. In fact, it is the BEST way to get calcium safely. When your mother said, drink your milk for strong bones, her common-sense approach was far better than today’s recommendation to swallow horse pills of calcium. If you don’t like or can’t tolerate milk, there are other options. Here are some non-dairy sources of calcium:

  • Almonds
  • Beans
  • Broccoli
  • Bok Choy
  • Corn Tortillas
  • Fortified Orange Juice
  • Kale
  • Mustard Greens
  • Salmon (canned, bone-in)
  • Sardines
  • Spinach
  • Swiss Chard
  • Tofu
  • Turnip Greens

Our Guide to Osteoporosis discusses some of the other things you can do to reduce your risk of weakened bones.

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  1. Gail

    I’m glad you included canned salmon with bones. Many recipes using canned salmon say to remove skin and bones. This is not necessary. The bones are quite soft and a good source of calcium. I never remove the skin, either, but I suppose that’s a matter of taste.

  2. BriCorn

    My understanding is that Vitamin D may help absorb Calcium, but Magnesium is the “horse that carts it around” in your body. Without Mg the Ca isn’t mobile–and in any case, the presence of enough magnesium will make sure the blood calcium is fairly level, so testing blood for calcium levels isn’t really a great test — if there isn’t enough calcium in the blood, the magnesium will go to the bones and teeth to get the necessary calcium needed for proper nerve and muscle function. So perhaps it is the magnesium and the calcium levels that should be studied and addressed? Most people are short of magnesium, leading to muscle cramping and jumpy legs…because the calcium transporter is not present.

  3. Jj

    What about fosamax? My doctor wants me to take it because of osteopenia, I have heard bad things about it and I don’t want to take. What can I do as alternative? Thank you

  4. Linda

    So what can we do if we think our arteries are clogged with calcium?

  5. Elizabeth Hillerstrom
    Cary, NC

    Would the calcium derived from cocoanut milk be considered to be supplemented calcium, assuming it is added to the milk in processing? (unless cocoanuts provide calcium?) I assume the calcium in almond milk would probably derive from the almonds themselves.

  6. dj

    Can you please state how much and in what form you were using of calcium I am having joint problems also.

  7. SJS

    I would counter these findings depending on the bio-availability of the calcium product used. My understanding is that these forms of calcium are not readily bio-available. I would also like to know who funded the study published in JAMA.

  8. Russ1a

    Regarding the post from MJM, I totally agree.
    When speaking of calcium metabolism, the first consideration is: how much calcium is in the diet? The next consideration is: how much of that calcium is actually absorbed from the gut? Vitamin D is the gatekeeper of how much calcium is absorbed from the gut. If you are a child and you have too little vitamin D, you will get rickets due to lack of absorbed calcium. If you are an adult and you have too little vitamin D, you will get osteomalacia from too little absorbed calcium.
    The next question is: What is the fate of blood calcium if you have enough vitamin D? This is greatly affected by how much vitamin K2, and I am not referring to K1, you have on board. If you have enough K2, the calcium will go to the bones, and if not enough, some of the calcium will be deposited in the arteries, See: Vitamin K2 prevents Cardiovascular Disease and maintains Bone Strength: http://www.vitak.com/index.php/background6 . If I quote the whole page, this post will probably never get published, so I will just give you one short snippet:
    “Now, new clinical research carried out by researchers of VitaK at the University of Maastricht revealed that vitamin K2 can stop the calcification of the arteries and may actually even reverse it (Schurgers et al.). The new study is published this month in the American Hematology Society Journal Blood. According to Dr. Leon Schurgers “arterial calcification is a major and independent risk factor for cardiovascular mortality. This new study demonstrated that in rats with existing arterial calcifications the total amount of aortic calcium could decrease by 37% in 6 weeks during a high vitamin K2 diet”.”
    On the topic of the study: Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality, the Relative Risk in men is in the form of a U shaped curve for total intake of calcium which includes food plus supplements, where the lowest risk is approximately at 1000 mg/day. The median intake from food in the middle quintile is nearly 750 mg/day. That leaves a beneficial supplement of 250 mg/day. Supplementation above that progressively increases the Relative Risk. I emailed the lead author of the study, Dr. Qian Xiao, inquiring if vitamin K2 had been considered in the study; and he replied that it had not. So as far as I’m concerned, an absolutely critical factor in calcium metabolism reported in this study is not addressed, and I would wait for studies which include the effect of vitamin K2 before I put much faith in the study’s conclusions, as I take approximately 200 mcg/day of K2 in the form of natto.
    Regarding the recommendation of Fortified Orange Juice
 as an alternate source of calcium, I cannot agree. IMHO, the concentrated fructose in the orange juice is detrimental to health, by being the primary cause of the Metabolic Syndrome. See youtube for “Sugar, the Bitter Truth”: https://www.youtube.com/watch?v=dBnniua6-oM , and “Dr. Mercola Interviews Dr. Richard Johnson About The Fat Switch” https://www.youtube.com/watch?v=3W2zSN0JOa8 .
    Sincerely, Russ S.

  9. Danielle R. R.

    Hi thank you so much for the wonderful work you do.
    I have Fibromyagia and need to take about 400 mgs of Magnesium. I was taking 600 mgs of Calcium with it, but since I read the articles about calcium I threw the pills out. Then I had muscle drawing and pulling in the groin area and thought I had restless legs for awhile.
    I thought about it and tried a 1 1/2cup serving of Greek Yoghurt and the misery stopped. So should I just try to figure out how much milk and yoghurt I need per day and avoid the pills?

  10. M. A. Lawnicki

    It’s great to see someone shedding light on health issues related to calcium supplements. Several years ago, a family member was suffering from kidney stones, and her doctor suggested that they were caused by too much calcium. That’s what prompted me to do extensive research into nutritional supplements and ultimately led to the publication of my book, The Day I Stopped Taking Vitamins. There’s no doubt in my mind that the best source of calcium is good old-fashioned food.

  11. Karen

    > but surely they must be different from other calcium supplements?
    In some cases, I would agree with your naturopath, but in the case of calcium (and vit C), I’m not so sure. The fact that there are a number of different compounds used for calcium supplementation doesn’t do much to change what happens to an excess of calcium in the bloodstream, when all the other supporting players in the bone health story are not there.
    OTOH, if you’re eating enough “whole food sources” to get all the magnesium, silica, D3 (not possible) and vitK that are required to maintain bone, PLUS getting load-bearing exercise, PLUS no history of extreme dieting or anorexia / bulimia, PLUS no family history of osteoporosis (and even even better, history of NO osteoporosis* which is not the same thing), AND you don’t take acid suppressing PPIs, AND you don’t drink sodas, you might be ok.
    *that is, women lived long enough to be in the risk pool for osteoporosis and didn’t get it; if they died young you can’t say you have no history of o.

  12. PP

    To deal with leg cramps my husband takes magnesium and Potassium. This last really made a difference for him. But you don’t want to take potassium if you are on an ACE-inhibitor for high blood pressure.
    PEOPLE’S PHARMACY RESPONSE: We don’t generally recommend taking potassium except under medical supervision. Too much is just as dangerous as too little. And you are right, PP, about ACE inhibitors. Others who are trying to prevent leg cramps might want to try eating more high-potassium foods, especially vegetables.

  13. Cindy B.

    I mentioned to a naturopath my concerns about calcium supplementation shortly after the negative studies came out (about a year ago). She replied, without hesitation, that calcium supplements marked “from whole food sources” were not dangerous like the others were. They are still supplements, but surely they must be different from other calcium supplements? Anyway, I never see anything about this in any discussion thread.

  14. MaryAnne

    My RA doctor has told me to take 3 Calcium Citrate pills with D3 each day plus one 500mg of D3. He has also has me on 3 Omega 3 fish oil capsules per day.
    I also take Kirkland’s multi-vitamin Equal to Centrum Silver along with enteric fish oil. Is it possible that the fish oil helps to eliminate or counter act the of build up of calcium in the heart and veins? I have bone scans once or twice each year. I also take Leflunomide each evening.

  15. Mikey

    MY internist & I were pretty happy with my overall health, but a fancy micronutrient test showed a calcium deficiency and marginal zinc level. So I’m now taking a Ca (333mg) + Zn (5mg) supplement, which also includes Mg (133mg) and vitamin D3 (200IU). Our feeling was, “it can’t hurt”, but now maybe I’m not so sure. I don’t notice any difference.
    Interesting to read about the vitamin K relationship to Ca; why wouldn’t the Ca supplement include some? But I’m getting 30mcg of vitamin K from my daily multivitamin, so maybe I’m good. But it’s too expensive to test regularly for levels of everything that might matter, and what “might matter” usually isn’t based on sound science, but simply observation of test groups. This is all very confusing.

  16. Mary

    This situation is very confusing. What to do? What to do? Would you please do a program very soon devoted to the subject of calcium. My bone density is below what it should be. I stopped Foxomax because of its side effects and have been taking calcium regularly. Is it possible to get all the calcium we need from our diet? Thanks.
    PEOPLE’S PHARMACY RESPONSE: You may be interested in a show we did a couple of years ago: Bone Vitality

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