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Harvard Commentaries on Health


Calcium – The Food vs. Supplement Debate

Calcium is the most abundant mineral in the body. Ninety-nine percent can be found in the human skeleton where it works to build and maintain strong bones and teeth. But calcium serves other important roles as well. The remaining 1% functions in blood clotting, nerve conduction and muscle contraction.

Calcium is naturally found in foods, added to others like juice and is available as dietary supplements.

Below is some information on calcium and calcium supplementation.

How much calcium do I need?

The amount of calcium you need depends on your age and whether you are pregnant or breast-feeding.

The table below shows the Recommended Daily Allowances (RDAs) for the amount of calcium required for healthy individuals.

Age

Male

Female

Pregnant

Lactating

0-6 months*

200 mg

200mg

 

 

7-12 months*

260 mg

260 mg

 

 

1-3 years

700 mg

700 mg

 

 

4-8 years

1,000 mg

1,000 mg

 

 

9-13 years

1,300 mg

1,300 mg

 

 

14-18 years

1,300 mg

1,300 mg

1,300 mg

1,300 mg

19-50 years

1,000 mg

1,000 mg

1,000 mg

1,000 mg

51-70 years

1,000 mg

1,200 mg

 

 

71+ years

1,200 mg

1,200 mg

 

 

*Adequate Intake (AI)

Which foods contain calcium?

Dairy provides rich, natural sources of calcium and is the major contributor of dietary calcium intake in the United States. But for those who cannot tolerate dairy, are lactose intolerant, or simply don't like the taste of milk-based products, other food sources of calcium are available. The list includes certain vegetables, beans, nuts and soy. Products such as fruit juices, non-dairy drinks, tofu and cereals have now been fortified with calcium.

Dairy Foods

Yogurt, plain, low fat (1 cup, 8 oz.)

450 mg

Ricotta cheese, part skim (1/2 cup)

340 mg

Milk, 1% fat (1 cup, 8 oz.)

305 mg

Cottage cheese, 2% fat ( 1/2 cup)

105 mg

Cheddar cheese (1 oz.)

205 mg

Soy Products

Tofu, firm or extra firm with calcium (1/2 cup)

250 mg

Soy milk enriched with calcium (1 cup)

300 mg

Soy yogurt with calcium (1 cup)

300 mg

Soy nuts, roasted/salted (1/2 cup)

120 mg

Edamame (1 cup)

260 mg

Nondairy Foods

Whole Grain Total cereal (3/4 cup)

1000 mg

Cheerios, Multi-Grain cereal (1 cup)

100 mg

Pink salmon, canned, with bones (3 oz)

185 mg

Sardines, canned, with bones (3 oz)

325 mg

Black beans (1/2 cup)

45 mg

Almonds, dry roasted (1 oz)

75 mg

Broccoli, cooked (1 cup)

60 mg

Kale, cooked (1 cup)

95 mg

Should I take a calcium supplement?

Calcium supplementation has been a standard of care for the prevention and treatment of osteoporosis. According to NHANES 2003-2006, about 43% of the U.S. population (with almost 70% as older women) uses dietary supplements containing calcium.

But new research out of Europe questions the safety of this widespread practice. A study recently published in the journal HEART found that individuals who took calcium supplements had a higher risk of heart attack when compared to those who did not take calcium supplements. The risk was more pronounced in those individuals who took only calcium supplements and no other supplements.

The findings of this study are consistent with the results of a New Zealand meta-analysis, which first suggested a possible link between calcium supplements and cardiovascular disease risk 2 years ago. Using data from the Women's Health Initiative Calcium/Vitamin D Supplementation Study (WHI CaD Study), the authors found that calcium supplements, whether with or without Vitamin D, increased the risk of cardiovascular events, particularly heart attack. Furthermore, when comparing the benefits of calcium supplementation on fracture prevention with the risk of cardiovascular events, the risks outweighed the benefits. In their analysis, they concluded that for every 1000 patients treated with calcium or calcium with vitamin D for five years, 6 additional myocardial infarctions or strokes would occur and only 3 fractures would be prevented.

With the widespread use of calcium supplements, this modest increase in risk of cardiovascular events may translate to a substantial burden of disease in the population, particularly among older individuals. Revaluation of the role of calcium supplementation in the prevention and treatment of osteoporosis may be warranted.

There is also another reason to be cautious of calcium supplementation. Kidney stones in the urinary tract are commonly made from calcium oxalate. Some studies suggest a positive association between supplemental calcium intake and kidney stone formation. In the Women's Health Initiative study, postmenopausal women who were supplemented with 1000 mg of calcium with 400 IU of Vitamin D for 7 years had a 17% greater risk of developing kidney stones than participants who were given a placebo.

Are calcium-rich foods safe to eat?

The research suggests that the sudden rise in blood calcium levels after supplementation may be the driving force for increasing cardiovascular disease risk. Observational studies have linked increased blood calcium levels with higher heart attack rates. When calcium builds up in the blood it can lead to plaque accumulation in the arteries, which is a precursor to atherosclerosis and other cardiovascular disease.

The good news is that calcium-rich foods do not have the same effect. Calcium, when obtained through the diet, enters the bloodstream slowly, causing a more gradual rise in serum levels.

The good news also extends for calcium-rich foods and kidney stone formation. In fact, higher intakes of dietary calcium not only appear not to cause kidney stones but it might actually protect against developing them.

Other Considerations for Calcium

  • Not all calcium consumed is absorbed. The body can absorb about 500 mg of calcium at one time. Therefore it is best to spread your intake of calcium-rich foods throughout the day.

  • Vitamin D enhances calcium absorption. Make sure to maintain optimal vitamin D blood levels. This can be done through diet, supplementation and appropriate sun exposure.

  • Oxalic and Phytic Acids found in whole grains, dark leafy vegetables, peanuts and soy beans decrease the absorption of calcium in these foods.

  • Phosphoric acid in dark sodas can interfere with your body's absorption of calcium.

  • Prolonged use of magnesium-containing laxatives compromises calcium absorption.

  • Caffeine increases calcium lost in the urine. Limit consumption to one to two cups of caffeinated coffee, soda or tea per day.

  • Excess sodium in the diet also increases calcium excretion. Every 500 mg of sodium over 2,400 mg per day causes the body to excrete 10 mg of calcium.

  • The efficiency of calcium absorption decreases with age. Recommended calcium intakes are therefore higher for older adults. Make sure to check out the table above for the RDA for your age group.

  • Maintaining a healthy weight, performing resistance training at least twice per week, and not smoking are important factors for good bone health.

The bottom line

Calcium is needed for healthy bones, teeth, nails and muscle tissue. It also assists in heart and nerve functioning and blood clotting. Given the uncertain benefits and possible risk of cardiovascular disease from supplementation, calcium is best obtained through diet (food sources). However, certain circumstances may warrant the need for calcium supplementation. It is important to speak to a doctor, pharmacist, or nutritionist before starting a calcium supplement.

Sources:

  1. Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.

  2. U.S. Department of Agriculture, Agricultural Research Service. 2011. USDA National Nutrient Database for Standard Reference, Release 24. Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/ba/bhnrc/ndl.

  3. Kuanrong Li, Rudolf Kaaks, Jakob Linseisen, Sabine Rohrmann. Associations of dietary calcium intake and calcium supplementation with myocardial infarcation and stroke risk and overall cardiovascular mortality in the Heidelber cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelber). Heart. 2012; 98:920-925.

  4. Bolland MJ, Grey A, Avenell A, Gamble GD, Reid IR. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis. BMJ. 2011 Apr 19;342:d2040.

  5. Jackson RD, LaCroix AZ, Gass M, Wallace RB, Robbins J, Lewis CE, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med 2006;354:669-83.

  6. Curhan GC, Willett WC, Speizer FE, Spiegelman D, Stampfer MJ. Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. Ann Intern Med. 1997 Apr 1;126(7):497-504.

  7. Curhan G, Willett WC, Rimm E, Stampher MJ. A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med 1993;328:833-8.

Author: Anne Chiavacci
Author: Anne Chiavacci, M.S., M.A., R.D., L.D.N.
Date Last Reviewed: 7/24/2012
Date Last Modified: 7/24/2012
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