A Warning About Calcium Supplements

Women who take calcium supplements in addition to having a high-calcium diet may be at increased risk of death from all causes, and particularly from cardiovascular disease and ischemic heart disease, according to research recently published in the journal BMJ. Cardiovascular disease is the leading cause of death in people with diabetes.

Calcium intake guidelines have generally focused on preventing low levels of calcium, and indeed, more than 60% of middle-age and older women in the United States now regularly take calcium supplements to preserve bone health (calcium is important for strong bones). But reanalysis of some recent studies has indicated a higher risk of ischemic heart disease (a condition in which there is a reduced supply of blood to the heart) and stroke with calcium supplements.


To evaluate the effect of dietary and supplemental calcium intake on cardiovascular health and mortality, researchers at Uppsala University in Sweden followed 61,433 women born between 1914 and 1948 for nearly two decades. The participants’ diets were determined by questionnaires administered to all the women at the start of the study and to 38,984 of the women approximately 10 years later. The participants were divided into four groups based on their calcium consumption: less than 600 milligrams (mg) a day, from 600 mg to 999 mg a day, from 1,000 mg through 1,399 mg a day, and 1,400 or more mg daily (equivalent to about five 8-ounce glasses of cow’s milk).

Over the course of the 19-year follow-up, 11,944 of the participants died, 3,862 from cardiovascular disease, 1,932 of ischemic heart disease, and 1,100 of stroke. Compared to women with a calcium intake of 600 mg to 999 mg daily, those consuming more than 1,400 mg each day had 1.40 times the risk of death from any cause, 1.49 times the risk of death from cardiovascular disease, and 2.14 times the risk of death from any cause. There was no significant difference in death rate from stroke. Levels of calcium intake below 600 mg a day were associated with an increased risk of death from all causes, plus death from cardiovascular disease, ischemic heart disease, and stroke.

In a separate analysis using the data from the 1997 survey, the researchers found that women with a dietary calcium intake of 1,400 mg or more daily who also took a calcium tablets (500 mg of calcium) had a 2.57-fold risk of death from all causes compared to women with a calcium intake of 600 mg to 999 mg daily. Further analysis revealed that, in women with a high dietary intake of calcium, the addition of a calcium supplement increased the risk of death in a dose-dependent fashion.

“The increase was moderate with a high dietary calcium intake without supplement use, but the combination of a high dietary calcium intake and calcium tablet use resulted in a more pronounced increase in mortality,” the study authors noted.

According to the researchers, diets very high or very low in calcium might affect the body’s equilibrium, causing changes in the blood levels of calcium. They emphasized that mortality was not increased with customary levels of calcium intake.

Limitations of the study include that it was observational, meaning it could not establish cause and effect, and that the results may not apply to people of different ethnic origins or to men. (The recent NIH-AARP Diet and Health Study, however, has linked high calcium intake from supplements to heart disease in men. To learn more about that study, click here.)

To learn more, read the article “Calcium Supplements Can Spell Heart Trouble for Women” or see the study in the journal BMJ. And for more information on how to keep your heart healthy, click here.

  • Joe

    I read a summary of the NIH-AARP Diet and Health Study about the heart-calcium connection in men and am quite concerned as the nutritionist at my urologist office wants me taking large doses of calcium citrate to reduce kidney stone risk. I’m pretty sure I’d rather have another kidney stone than another heart attack. What to do when medical advice conflicts?

  • Janice Mix

    I have osteopenia and am at risk for osteoporosis.What am I supposed to do if calcium is dangerous for me?

  • Joan Hunnicutt

    Any answer to Janice Mix’ question on March 6. I think there are many of we elders who are concerned with that very thing.

    Please respond to me at the above email.

    Thank you,

    Joan Hunnicutt

  • Ferne

    This report is rather disturbing when the doctors say to take 1200 mg with Vit K in two divided doses daily. Most of my calcium from food comes from yogurt and string cheese. So what is the answer? I am almost 80 and have higher than normal bone density which I think helps prevent bone fractures because I have a balance problem with frequent falls. I’m really puzzled now as to what I should do. If the above article is true I shouldn’t be taking any calcium supplements but I’m a little skeptical about the findings. I guess wait another week and another report will come out disagreeing with this one. That seems to be the way it goes with foods and meds.

  • theodore cole

    If you take between 500 – 1,000 mg of magnesium per day, your risk of kidney stones will be reduced by 90%. Also, to the lady, if you take at least 2,000 iu of vitamin D3 per day, you should be able to take a moderate level of calcium per day. (700-800mg)with good results. Vitamin K2 is also very helpful in getting the calcium where it belongs!
    1. Life Extension Magazine Sept. 2010, Brittle bones …
    2. Dr. Wright’s Book of Nutritional Therapy, Rodale Press 1979. Dr. Jonathan V. Wright, M.D. p. 264 +
    3. Understanding Vitamins and Minerals Rodale Press, 1984. p. 113-114.

  • Lynne Nelson

    I have had osteopenia in my low back since 2001 and it has not become osteoporosis. I stopped taking calcium supplements about a year ago, but had previously cut back to 500 per day. I eat cottage cheese every morning and other cheese during the day plus plenty of green leafy vegetables. I can’t drink milk as I don’t tolerate it well. I did read that drinking any kind of carbonated beverage can be problematic for those with a tendency towards osteoporosis and have not used such beverages in many years.

    I also read sometime back that osteopenia is not an absolute indication that one will develop osteoporosis, although a former GP suggested that I take one of the drugs to correct osteoporosis. After looking up the side effects, I declined and I have since found a new doctor.
    Don’t despair. Just look up the vegetables that contain calcium and eat them every day.

  • Barbara Hollingsworth

    My husband just had thyroid surgery. He had the entire thyroid removed which was cancerous. In about 6 weeks, he’ll have the iodine pill treatment. He has had triple by-pass surgery in the past and sees a cardiologist regularly. He is also on a blood thinner – Coumadin.
    My concern is that it seems to be imperitive that he chew 3 Tums 3 times a day for awhile. His diet is calcium rich already. What effects will this have on his heart, etc.? Thank-you for your reply.

  • Diane Fennell

    Hello Janice and Joan,

    Thanks for your questions.

    Because this was an observational study, the researchers can only say that women who took calcium supplements in addition to having a high-calcium diet had a higher risk of death; they cannot say that the high calcium intake was necessarily the cause of the higher risk of death. Until further research can address this more conclusively, I would recommend printing out a copy of the study (linked in the last paragraph of the above article) to show to your doctor and asking for his guidance.

    You may also be interested in this chart, which lists foods that are rich in calcium.

    Diane Fennell
    Web Editor

  • Joclyn

    I was wondering if there was any possible danger taking a Calcium supplement. I’d noticed after taking a combination supplement of Calcium/Magnesium/Zinc later that night I’d noticed my upper back ached. So I stopped taking it. Several months later I tried taking it again thinking maybe it had nothing to do with the supplement, but same ache. So I stopped taking it completely. Well just recently I tried taking a multi-mineral supplement because I was hearing how important it is to make sure we’re getting enough minerals, and the same thing happened. (sigh) I’m 46.