Rethinking Calcium: Bone Health or Heartache?

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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

*ls 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.

--

Ortiz, MS, RD

*The FRUGAL Dietitian* <http://www.thefrugaldietitian.com>

Check out my blog: mixture of deals and nutrition

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