My Patients Ask — How do I get the right amount of calcium? Food or supplements?

I’m confused about the recommendation to get calcium from food rather than supplements. If one does this with calcium-fortified food (plant-based “milks”, orange juice, dairy products, cereals), wouldn’t that be the same as getting calcium from supplements?

This is a great question. Thanks for sending it along. Certainly, taking too much calcium in any form has potential harm. However, it’s very difficult to get too much calcium just from food sources whether fortified or not.

So, concentrating on food sources, whether fortified or not and keeping total daily intake below the upper recommended value, seems prudent. cautions in its plant-based milk review:

Nearly every plant-based milk [we tested] promises and delivers about as much calcium as regular 1% [cow’s] milk, which is about 325 mg per cup, and some deliver even more — up to 450 mg.

That’s a substantial portion of the recommended daily intake of calcium for adults of 1,000 mg to 1,200 mg.

But keep in mind that this calcium has been added, so, it’s like taking a calcium supplement rather that getting it naturally from milk.

Studies show that you can’t absorb more than 500 mg of calcium at a time and getting too much calcium from supplements (more than 1,000 per day) may increase the risk of stroke and heart attack, but this has not been seen with calcium from milk.

So, downing more than one cup of plant-based milk at a time, or drinking more than two or three cups per day, is not a good idea.

And, if you cannot get the recommended amount of calcium from food alone, low-dose supplementation with calcium carbonate seems reasonable — as long as the brand you purchase has been quality tested and does not contain contaminants such as lead.

Below is an FAQ sheet on calcium supplementation in adults from the doctors of pharmacology at the “Prescriber’s Letter.” Also, has a great review on calcium supplements.

© Copyright WLL, INC. 2021. This blog provides a wide variety of general health information only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment from your regular physician. If you are concerned about your health, take what you learn from this blog and meet with your personal doctor to discuss your concerns.



Calcium in Adults: FAQs. Pharmacist’s Letter/Prescriber’s Letter. January 2017.

As research increases our understanding of the relationship between calcium and health, questions arise about adequate calcium intake. There is even debate about whether calcium supplements cause more harm than good. The table below addresses frequently asked questions about calcium in adults, such as questions about dosing, benefits, and risks.

Abbreviations: CV = cardiovascular; MI = myocardial infarction; UL = tolerable upper limit

Clinical question
Pertinent Information
What is the physiologic role of calcium? Calcium is an important structural component of bones and teeth.1

  • Bones serve as a repository for calcium and help keep serum calcium levels within a tightly regulated range. Parathyroid hormone and calcitriol act on bones, the intestines, and the kidney to raise calcium levels when levels are low and are turned off through a feedback mechanism.1

Calcium plays a role in muscle contraction, blood vessel contraction/relaxation, nerve conduction, intracellular signaling, and hormone secretion.1

What are the consequences of calcium deficiency? Frank calcium deficiency is uncommon.2 Hypocalcemia is usually secondary to diseases or medications, such as renal failure, surgical removal of the stomach, or loop diuretics.2

Symptoms of hypocalcemia include muscle cramps, tingling in the fingers, lethargy, anorexia, arrhythmias, or seizures.2

Long term, inadequate calcium intake can lead to osteopenia, osteoporosis, and fractures.2

What are the recommendations for total daily calcium intake (food and/or supplements) in adults? National Osteoporosis Foundation: 1000 mg per day (1200 mg for women 51 years and older, and men 71 years and older)3

North American Menopause Society: 1200 mg per day for most postmenopausal women.4

Institute of Medicine and Health Canada (19 years and older): 1000 mg per day (1200 mg for women 51 years and older, and men 71 years and older)1,5

Can adults get adequate calcium from food? Yes.5

Teach patients to read food labels. If the label provides calcium in a percentage of the Daily Value (DV), it is based on 1000 mg of calcium per day. For example, 30% DV of calcium = 300 mg.3

People typically get about 250 to 300 mg/day of calcium from their diet, not including dairy products.11,25 Several foods can provide 300 mg or more of calcium per one-cup serving. These include milk (290 mg to 315 mg) and low-fat yogurt (340 mg to 450 mg). For people who wish to avoid dairy, choices include cooked collard greens (300 mg to 350 mg) and calcium-fortified foods (e.g., soy milk [80 mg to 300 mg], cereal [up to 1000 mg], or fruit juice [225 mg to 300 mg]). Breakfast bars often contain 200 mg to 500 mg.4

A guide to calcium-rich foods is available at

calcium calculator is available at

Which adults need to take a calcium supplement? The patient’s need for a supplement depends on the amount of calcium the patient gets from food. Patients should first calculate the amount of calcium they get from food, then supplement only to make up any deficit.3

  • For example, people typically get 250 to 300 mg per day of calcium from their diet, not including dairy products.11,25  If the patient can include two servings of high-calcium foods (e.g., dairy) each day, they can get a total of at least
    900 mg per day. Supplementation with just 300 mg of elemental calcium daily, or the addition of a third high-calcium serving, will then provide 1200 mg per day.
  • A chart to help patients estimate their calcium intake is available at
What calcium supplements are available, and how should they be taken? The amount of elemental calcium supplied by supplements varies depending on the salt form. Calcium carbonate and calcium citrate provide the most elemental calcium (see below). Other calcium salts are impractical sources of calcium due to low amounts of calcium provided (e.g., calcium gluconate, calcium lactate),24 or lack sufficient safety and efficacy information (e.g., calcium D-glucarate [U.S.]).12 Calcium acetate is used as a phosphate binder in renal disease.

Calcium carbonate is 40% elemental calcium.4 Calcium carbonate dissolves best in an acidic environment.13 But whether its absorption is significantly impaired by acid-reducing drugs such as proton pump inhibitors, or in the elderly, is unclear.13

Calcium citrate is only 21% elemental calcium,4 but compared to calcium carbonate, it is better absorbed.13 This is likely because it dissolves better than calcium carbonate in the high-pH environment of the ileum, the main site of calcium absorption.13

Some products contain other ingredients (e.g., magnesium, vitamin K), but there is no proof they work better than those with just calcium.

It is generally recommended that calcium carbonate should be taken with food to improve absorption.2 However, certain foods (e.g., spinach, rhubarb, nuts, beans, seeds, wheat bran) or high fiber meals may decrease absorption.2

Calcium absorption is best if no more than 500 mg is taken at a time.2

There is concern that some coral calcium products (a source of calcium carbonate) contain excess lead.12 Dolomite supplements (another source of calcium carbonate) may also contain unsafe amounts of lead and other heavy metals.12 The lead content of oyster shell and refined calcium products is considered to be clinically insignificant.12 Advise U.S. patients to look for supplements with the USP (United States Pharmacopeia) Verified mark to ensure the product meets purity and quality standards.3 In Canada, look for a product with a Natural Product Number (NPN).

Might an adult taking a calcium supplement get too much calcium, with diet? The UL is the highest average daily intake that is likely to pose no risk to most people.1 The UL for calcium is 2000 mg/day for people 51 years and older, and 2500 mg/day for adults 19 to 50 years.2

Getting too much calcium from foods alone is rare.2

Around 5% of women over 50 years of age have estimated total calcium intakes from food plus supplements that exceed the UL.2

Does calcium supplementation prevent fractures in the elderly? Evidence that calcium supplementation reduces fracture risk is “weak and inconsistent.”18 The United States Preventative Services Task Force (USPSTF) has concluded that there is insufficient evidence to recommend the use of calcium and vitamin D supplements for primary fracture prevention in premenopausal women, men, or in community-dwelling postmenopausal women.14 Furthermore, there is no benefit of supplementing with ≤400 IU/day of vitamin D or ≤1000 mg/day of calcium in community-dwelling postmenopausal women.14

Hip and nonvertebral fracture reduction has been demonstrated with daily supplementation with vitamin D 800 IU and calcium 1200 mg in nursing home residents with vitamin D deficiency and low dietary calcium intake.15

Does calcium supplementation have non-musculoskeletal benefits? Calcium supplementation might moderately help prevent colorectal adenomas, but there is not enough evidence to recommend calcium supplements for this purpose.16
Does calcium pose CV risk?
Signals that calcium might be associated with an increase in CV risk first became evident in large cohorts, such as the Iowa and Boston women’s health studies.6 No prospective RCT studies have been done to examine the effect of calcium on CV risk. In theory, calcium could increase CV risk by causing vascular calcification.7 Supplements (as opposed to dietary calcium) might cause a spike in serum calcium concentrations that acutely adversely affects blood coagulability or flow.7,10 Levels of fibroblast growth factor 23 and inflammatory cytokines are also increased by high levels of calcium.10

In a secondary analysis of an RCT (n = 1471 postmenopausal women) designed to test the effect of calcium 1000 mg daily vs placebo on fracture risk and bone mineral density, event rates for the composite endpoint of MI, stroke, or sudden death were 23.3 per 1000 person-years and 16.3 per 1000 person-years for the calcium and placebo groups, respectively (p=0.043).6

A subsequent meta-analysis of RCTs of supplemental calcium 500 mg daily or more in almost 12,000 patients 40 years of age or older found that supplemented patients had about a 30% increased risk of MI.7 Among patients allocated to calcium supplementation, the risk of MI was higher in patients whose dietary calcium intake was above the median.7

A German cohort study (n=25,540) found that patients who took a calcium supplement, either as calcium only or as part of a multivitamin, had almost twice the MI risk of nonusers (HR 1.86, 95% CI 1.17 to 2.96; HR 2.39 95% CI 1.12 to 5.12 for a calcium-only supplement).8

A large U.S. cohort study (n=388,229) of AARP members (American Association of Retired Persons) found that among men, calcium supplementation of more than 1000 mg per day was associated with increased risk of total CV disease death (RR 1.20, 95% CI 1.05 to 1.36) and heart disease death (RR 1.19, 95% CI 1.03 to 1.37).9 Calcium supplements were not associated with increased CV mortality in women.9 Dietary calcium intake was not associated with CV mortality in men or women.9

A large Swedish cohort study (n=61,433) found that compared to intakes between 600 and 1000 mg per day, dietary calcium intake above 1400 mg per day was associated with modestly increased all-cause mortality (HR 1.4, 95% CI 1.17 to 1.67), CV disease death (HR 1.49, 95% CI 1.09 to 2.02), and ischemic heart disease death (HR 2.14, 95% CI 1.48 to 3.09). Furthermore, calcium supplement users with dietary calcium intake above 1400 mg per day had an HR for all-cause mortality of 2.57 (95% CI 1.19 to 5.55).  These findings suggest that recommendations for calcium supplementation should be individualized based on dietary calcium intake.

The National Osteoporosis Foundation and the American Society for Preventive Cardiology commissioned a systematic review and meta-analysis to determine the effect of calcium on CV disease in healthy adults.17  They concluded, that based on moderate-quality evidence, calcium intake (dietary + supplement) that does not exceed the UL poses neither cardiovascular harm (MI, stroke, or death) nor benefit for generally healthy adults.17,19

Does calcium cause dementia? A Swedish cohort study followed 700 elderly women for five years. Those who took a calcium supplement had a higher risk of developing dementia (OR 2.10, 95% CI 1.01 to 4.37, p = 0.046) and stroke-related dementia (OR 4.4, 95% CI 1.54 to 12.61, p = 0.006).23 Upon subgroup analysis, it was noted that the risk was only significant in women with a history of stroke or white matter lesions.23 In theory, calcium could increase dementia risk by causing vascular calcification.23  Supplements (as opposed to dietary calcium) might cause a spike in serum calcium concentrations that acutely adversely affect blood coagulability or flow, or hasten programmed cell death.23 Due to study limitations, it cannot be concluded based on this study that calcium causes dementia. More study is needed.23
Does calcium cause prostate cancer? Some cohort studies have found an association between prostate cancer and calcium intake as little as >600 mg daily.20,21 Overall, results from observational studies suggest that total calcium intakes >1,500 mg/day or >2,000 mg/day may be associated with increased prostate cancer risk (particularly advanced and metastatic cancer) compared with lower amounts of calcium (500 to 1,000 mg/day).2 The authors of a meta-analysis of prospective studies concluded that high intakes of dairy products and calcium might slightly increase prostate cancer risk.22

Because dairy products are a major source of calcium, the contribution of some other dairy component cannot be ruled out.21 However, the involvement of calcium is plausible. High calcium levels suppress vitamin D synthesis, and vitamin D may protect against prostate cancer by inhibiting its growth and metastasis.

Does calcium cause kidney stones? A high intake of calcium from supplements may increase the risk of kidney stones.2  In fact, this was used as the basis for setting the UL for calcium in adults.2

In the Women’s Health Initiative, postmenopausal women who consumed 1,000 mg of supplemental calcium and 400 IU of vitamin D per day for seven years had a 17% higher risk of kidney stones than those taking a placebo. The Nurses’ Health Study also showed a positive association between supplemental calcium intake and kidney stone formation.2

High intakes of dietary calcium may actually protect against developing kidney stones.2

Project Leader in preparation of this clinical resource (330107): Melanie Cupp, Pharm.D., BCPS


  1. IOM (Institute of Medicine). Dietary reference intakes for calcium and vitamin D. Washington, DC: The National Academies Press; 2011.
  2. National Institutes of Health. Office of Dietary Supplements. Calcium. Dietary supplement fact sheet. Health professionals. Updated November 17, 2016. (Accessed November 30, 2016).
  3. National Osteoporosis Foundation. How much calcium do you need? (Accessed December 1, 2016).
  4. North American Menopause Society. The role of calcium in peri- and postmenopausal women: 2006 position statement of the North American Menopause Society. Menopause 2006;13:862-77.
  5. Health Canada. Vitamin D and calcium: updated dietary reference intakes. March 22, 2012. (Accessed December 1, 2016).
  6. Bolland MJ, Barber PA, Doughty RN, et al. Vascular events in healthy older women receiving calcium supplementation randomised controlled trial. BMJ2008;336:262-6.
  7. Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010;341:c3691.
  8. Li K, Kaaks R, Linseisen J, Rohrmann S. 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 2012;98:920-5.
  9. Xiao Q, Murphy RA, Houston DK, et al. Dietary and supplemental calcium intake and cardiovascular disease mortality: the National Institutes of Health-AARP diet and health study. JAMA Intern Med 2013;173:639-46.
  10. Michaelsson K, Melhus H, Warensjo Lemming E, et al. Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study. BMJ 2013;346:f228. doi: 10.1136/bmj.f228.
  11. National Osteoporosis Foundation. Steps to estimate your calcium intake. (Accessed December 2, 2016).
  12. Jellin JM, Gregory PJ, et al. Pharmacist’s Letter/Prescriber’s Letter Natural Medicines Comprehensive Database. (Accessed December 1, 2016).
  13. Van der Velde RY, Brouwers JR, Geusens PP, et al. Calcium and vitamin D supplementation: state of the art for daily practice. Food Nutr Res 2014 Aug 7;58. doi: 10.3402/fnr.v58.21796.
  14. Moyer VA, on behalf of the U.S. Preventive Services Task Force. Vitamin D and calcium supplementation to prevent fractures in adults: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2013;158:691-6.
  15. Chapuy MC, Arlot ME, Duboeuf F, et al. Vitamin D3 and calcium to prevent hip fractures in the elderly women. N Engl J Med 1992;327:1637-42.
  16. Weingarten MA, Zalmanovici A, Yaphe J. Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps. Cochrane Database Syst Rev. 2008 Jan 23;(1):CD003548.
  17. Chung M, Tang AM, Fu Z, et al. Calcium intake and cardiovascular disease risk: an updated systematic review and meta-analysis. Ann Intern Med 2016 Oct 25. doi: 10.7326/M16-1165.
  18. Bolland MJ, Leung W, Tai V, et al. Calcium intake and risk of fracture a systematic review. BMJ 2015 Sep 29;351:h4580. doi: 10.1136/bmj.h4580.
  19. Kopecky SL, Bauer DC, Gulati M, et al. Lack of evidence linking calcium with or without vitamin D supplementation to cardiovascular disease in generally healthy adults: a clinical guideline from the National Osteoporosis Foundation and the American Society for Preventive Cardiology. Ann Intern Med 2016 Oct 25. doi: 10.7326/M16-1743.
  20. Chan JM, Stampfer MJ, Ma J, et al. Dairy products, calcium, and prostate cancer risk in the Physicians’ Health Study. Am J Clin Nutr 2001;74:549-54.
  21. Giovannucci E, Liu Y, Stampfer MJ, Willett WC. A prospective study of calcium intake and incident and fatal prostate cancer. Cancer Epidemiol Biomarkers Prev2006;15:203-10.
  22. Gao X, LaValley MP, Tucker KL. Prospective studies of dairy product and calcium intakes and prostate cancer risk: a meta-analysis. J Natl Cancer Inst2005;97:1768-77.
  23. Kern J, Kern S, Blennow K, et al. Calcium supplementation and risk of dementia in women with cerebrovascular disease. Neurology 2016; 87:1674-80.
  24. Straub DA. Calcium supplementation in clinical practice: a review of forms, doses, and indications. Nutr Clin Pract 2007;22:286-96.
  25. Skinner ML, Simpson JA, Buchholz AC. Dietary and total calcium intakes are associated with lower percentage total body and truncal fat in young, healthy adults. J Am Coll Nutr 2011;30:484-90.

Cite this document as follows: Clinical Resource, Calcium in Adults: FAQs. Pharmacist’s Letter/Prescriber’s Letter. January 2017.

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