CALCIUM SUPPLEMENTS: LET’S GET THE FACTS RIGHT

Controversial headlines attract readers – which sells more advertising – but it’s wrong to lead with a headline that can cause readers to act against their own interests.  This is what Fox News, US News, and multiple other news sources did with identical headlines on February 13, 2013:  “Calcium Supplements may raise odds of heart death in women.”  Technically, the article (that is the same word for word on multiple websites) states that sometimes a calcium supplement could be harmful, but many women took the headline to mean they should stop taking all calcium supplements because they “… may raise odds of heart death in women.”    

The statement in the headline is true – in very specific circumstances that do not apply to most women – but the headline can also be read to suggest it’s risky to take any calcium supplement whatsoever. 

Yet another study of calcium intake

The press story refers to a Swedish study published February 12, 2013 in the online version of the British Medical Journal.  The abstract is available on line [click here].  The researchers reported cardiovascular mortality in women in relation to their calcium intake.  Calcium intake was estimated based on two surveys:  an initial survey taken between 1987 and 1990 when women were enrolled in the study, and a second survey in 1997. 

For their analysis, researchers classified women into four groups from low to high calcium intake: less than 600 mg per day, 600 to 999 mg per day, 1000 to 1399 per day, and 1400 or more mg per day. 

To put the article in perspective, it is important to know that the Institute of Medicine in the United States recommends 1000 to 1200 mg per day.  And, the same Swedish researchers previously reported that between 750 and 1025 mg calcium per day is enough to prevent osteoporotic fractures, i.e. broken bones because of weak bones [click here].

Very low and very high amounts of calcium are associated with higher mortality.

When they looked at death in relation to calcium intake, women in the very low group (less than 600 mg per day) and in the very high group (1400 or more mg per day) had an increased chance of dying from heart disease.

In contrast, there was no significant difference between the two middle groups, the women who had 600 to 999 mg per day and those who had 1000 to 1399 mg per day.  In fact, there was a consistent hint that the 1000 to 1399 did slightly better overall, but this did not reach statistical significance.

The effect of calcium supplements specifically

These results were the same whether a woman got her calcium through food in her usual diet (typically with a lot of dairy products) or used a calcium supplement or both.

They also looked at women who took calcium tablets (which are usually 500 mg per tablet in Sweden).  Women in the 1000 to 1399 group still had slightly lower risk of death even if part of their calcium was from a calcium supplement or calcium included in a multivitamin. 

Who increased their risk with calcium supplements?

Women who took over 1400 mg of calcium per day and had part of that calcium in the form of a calcium pill, had an increased risk of dying of heart disease. 

Who takes over 1400 mg calcium of calcium per day anyway?

The guidelines for dietary calcium are 1000 to 1200 mg per day.  However, some physicians and some nutritionists recommend much higher intake.  There is no data to support benefit from a higher daily intake of calcium, and as just reported, high amounts of daily calcium intake may be risky.

Confirmation from the AARP

In a quirk of timing, a separate study of 169,170 AARP women members published February 4, 2013 found no relation of total calcium to mortality [click here].  They also looked specifically at calcium supplements separate from total calcium, and, although it was not statistically significant, observed a slight trend toward higher heart death with more than 1000 mg of calcium supplement per day.  [The same study followed 219,059 men and found that over 1000 mg of calcium supplement per day was significantly associated with increased heart attack death, especially in men who smoked tobacco.]

Should I take a calcium supplement?

The key to whether you need a calcium supplement is how much calcium you already get through your usual diet.

As discussed extensively in a previous Perspective on Women’s Health [click here], your personal decision should be based on how much you use dairy products, broccoli and kale, or canned sardines on a regular basis.  (And believe it or not, according to the USDA, General Mills Total Raisin Bran Flakes have a lot of calcium).  You can estimate your daily calcium using the US Department of Agriculture website [click here]. 

If you eat sufficient dairy products daily – which means at least two servings of milk, cheese, yogurt, cottage cheese, or ice cream, etc. each day as part of your regular diet – you may not need a calcium supplement.  If you get less than two servings of dairy per day, it’s difficult to get enough calcium consistently, and your total intake may be less than 600 mg per day. According to this article, such low calcium intake would increase your risk of cardiovascular death, and you would benefit from a calcium supplement.

What should have been the headline?

An accurate headline for Fox News, US News, and the others would have been, “Super high dose calcium supplements appear harmful: usual recommendations for calcium intake are confirmed.”

It would not have drawn as much attention, but it also would not have been misleading.

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