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From Medscape Internal Medicine > Staying Well With Sandra Fryhofer, MD

Rethinking Calcium: Bone Health or Heartache?

Sandra A. Fryhofer, MD

Authors and Disclosures

Posted: 10/25/2010

Sandra A. Fryhofer, MD Clinical Associate Professor of Medicine, Emory University School of Medicine, Atlanta, Georgia; Past President, American College of Physicians, Philadelphia, This issue of "Staying Well" focuses on rethinking calcium recommendations. In the past, calcium concerns have focused on bone health and on how to get enough calcium. Adequate calcium intake recommendations developed by the Food and Nutrition Board at the Institute of Medicine say that children and teens 18 years of age or younger need 1300 mg daily, and adult men and women 19 to 50 years of age need 1000 mg daily. After age 50 years, the Institute of Medicine recommends even more calcium, and daily adequate intake increases to 1200 mg.[1,2] Now, a study in BMJ raises concern that supplemental calcium may have an inadvertent adverse outcome: It could hurt your heart.[3]

Calcium and Heart Woes

In this meta-analysis of 15 randomized blinded placebo-controlled trials. Dr. Mark Bolland from the University of Auckland in New Zealand and colleagues evaluated calcium supplement use (at least 500 mg daily) in more than 12,000 patients older than 40 years of age. The findings were surprising: The pooled results linked calcium supplement intake to a significant 30% increased risk for heart attack. A tendency to increased risk for stroke and sudden death was also seen, but this result was not significant. Of note, cardiovascular outcomes were not a primary endpoint in any of the individual trials. Proposed mechanisms for the higher risk include increased blood coagulability and decreased blood vessel compliance due to calcium buildup in the arterial wall. On the basis of these findings, the authors postulate that treating 1000 people with calcium for 5 years would prevent 26 fractures but cause an additional 14 heart attacks.^[3]

This is not the first time that Dr. Bolland has studied calcium intake and cardiovascular outcomes. Two years ago, results of a randomized placebo-controlled study of 1471 postmenopausal women were published that linked calcium supplements with greater cardiovascular risk.^[4] That 2008 study by Bolland and colleagues was included in their 2010 meta-analysis.

No Trials of Calcium Plus Vitamin D Were Included

The type of calcium supplement did not seem to matter, but the current meta-analysis looked at calcium supplements alone. Researchers did not include any trials looking at calcium plus vitamin D.

An accompanying BMJ editorial questions the role of calcium in bone health in reducing fractures. It even goes so far as to say that only patients with osteoporosis who are also taking medication for it should take calcium supplements, alone or with vitamin D ,and calls for further research on calcium supplement safety and efficacy.^[5]

The Women's Health Initiative evaluation of combined calcium and vitamin D found no effect on heart attack and stroke.^[6] A recent systematic review in Annals of Internal Medicine suggests that moderate to high doses of vitamin D may reduce cardiovascular risk, whereas calcium alone had no significant effect.^[7]

Back to Basics: Incorporating Adequate Calcium Into the Diet

This study has me rethinking how I talk to patients about calcium. Use of calcium supplements may be problematic from a cardiovascular standpoint. What about dietary calcium? The verdict from previous studies is good: No increased cardiovascular risk is linked to higher intake of dietary calcium.^[3] Adequate calcium intake recommendations refer to total daily intake; it does not mean the extra amount of calcium that should be added, but that's often what happens. Incorporating dietary calcium rather than taking supplements is a better way to meet adequate calcium intake recommendations.

Calcium Content of Foods: My Favorite Lists

When talking to patients about dietary calcium, it helps to have a calcium food content list. My favorite patient-friendly list of the calcium content of selected foods is in the patient education section of the UCSF Medical Center Website.^[8] It separates the calcium content of foods into the categories dairy, vegetables, fruits, legumes, grains, nuts and seeds, fish, and other (blackstrap molasses). A list on the Harvard University Health Services Website is also handy: It is only 2 pages long and includes calorie contents.^[9] The most comprehensive list of the calcium content of foods can be found on the US Department of Agriculture's Website, but at 25 pages, it is too long to download and hand out to patients.^[10]

Dietary Calcium Intake: Start With Dairy

If the goal is to consume 1000 mg calcium daily and you take in 3 servings of dairy and soy, you're almost there. For example:^[8]

• Milk (1 cup [8 oz]): 300 mg calcium
• Plain low-fat yogurt (1 cup [8 oz]): 400 mg
• Cheese (1 oz of cheddar or mozzarella): 200 mg
• Calcium-fortified soy milk (1 cup [8 oz]) 400 mg

Dietary Calcium Intake: Beyond Dairy

Encourage patients to go beyond dairy and incorporate vegetables, fruits, legumes, grains, nuts and seeds, and fish as dietary calcium sources. (Table).

Table. Nondairy Sources of Dietary Calcium^[8]

Vegetables	Acorn squash (1 cup): 90 mg Arugula (1 cup): 125 mg Broccoli (1 cup): 180 mg Chard or okra (1 cup): 100 mg Kale, raw (1 cup ): 55 mg Spinach, cooked (1 cup): 240 mg
Fruits	Figs, dried uncooked (1 cup): 300 mg Calcium-fortified orange juice (1 cup [8 oz]): 400 mg
Nuts	Sesame seeds, whole roasted (1 oz): 280 mg Almonds (1 oz): 80 mg
Fish	Canned mackerel (3 oz): 250 mg Sardines (3 oz): 370 mg
Other	Blackstrap molasses (1 tbsp): 135 mg

Rethinking Calcium Recommendations: Balancing Benefits and Minimizing Risks

Here's how I am rethinking what I tell my patients.

1. For bone health, I will still encourage adequate calcium intake, along with vitamin D, 1000 IU. Don't forget the "D."
2. I will spend more time talking to patients about dietary sources of calcium and discourage immediately turning to a calcium supplement.
3. Calcium supplements should be used to help patients attain total recommended intake, not to augment daily intake. (I prefer calcium citrate.)
4. This new study focuses on heart risks, but don't forget about kidney stones. Unlike supplements, dietary calcium is less likely to trigger stone formation.^[11]

So, add some figs and a spoonful of almonds to your salad, and also sprinkle on some sesame seeds. This new study is another reminder that too much of a good thing may be bad for you, even calcium.

References

1. Dietary Supplement Fact Sheet, Calcium: health professional fact sheet. Available at:http://ods.od.nih.gov/factsheets/Calcium_pf.asp Accessed September 22, 2010.
2. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academies Press; 1997.
3. Bolland MJ, Avenell A, Baron J, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010; 341:c3691.
4. Bolland M, Barber P, Doughty R, et al. Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial. BMJ. 2008;336:262-266. Abstract
5. Cleland JG, Witte K, Steel S. Calcium supplements in people with osteoporosis. BMJ. 2010;341:c3856.
6. Hsia J, Heiss G, Allison M, et al; Women's Health Initiative Investigators. Calcium/vitamin D supplementation and cardiovascular event. Circulation. 2007;115:846-854. Abstract
7. Wang L, Manson JE, Song Y, Sesso HD. Systematic review: vitamin D and calcium supplementation in prevention of cardiovascular events. Ann Intern Med. 2010;153:315-323.
8. USCF Medical Center. Calcium content of selected foods. USCF Medical Center Website. Available at:http://www.ucsfhealth.org/adult/edu/calciumContent/index.html. Accessed September 24, 2010.
9. Harvard University Health Services. Calcium content of common foods in common portions. Harvard University Health Services website. Available at:http://huhs.harvard.edu/assets/File/OurServices/Service_Nutrition_CalciumContentOfCommonFoods.pdf. Accessed September 24, 2010.
10. USDA US Department of Agriculture. National Nutrient Database for Standard Reference, Release 20. Calcium, Ca mg Content of Selected Foods per Common Measure, sorted alphabetically. Available at:http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20a301.pdf Accessed September 24, 2010.
11. Worcester EM, Coe FL. Clinical practice: calcium kidney stones. N Engl J Med. 2010;363:954-963.