To Calcium or Not to Calcium?

Two big studies that came out recently have muddied the waters on the one nutritional supplement that even conventional medicine has rallied behind:  calcium.

We’ve all heard that supplemental calcium is good for the bones, and may even protect against colon cancer in older adults.  Seems like a logical recommendation.  But like hormone replacement therapy, whose cardiovascular benefits were disproven ten years ago by the Women’s Health Initiative study, calcium supplements are now being called into question.

The first chink in the armor came a few weeks ago when a study sponsored by the National Institutes of Health (NIH) (1) found that supplemental calcium boosts the risk of death by cardiovascular disease (CVD) in men, but not women.  Men who consumed 1000 mg/day of calcium supplement had a 20% higher risk of CVD death than those who took no calcium.

OK, great… men, ditch the calcium; women, keep popping those ginormous horse pills.  Until February 13, when BMJ (British Medical Journal) (2) published the findings of Swedish scientists, who found that calcium supplements increased death rates in women, too.  Examining the findings more closely, though, we find some important details:  the all-cause mortality rates were doubled in women with a calcium intake of  more than 1400 mg/day, compared to those getting 600-1000 mg/day.  A further complication is that risk of death was increased if the calcium came from supplements rather than food.

The US Preventive Services Task Force (3) has also chimed in, with a re-analysis of older data that showed that 400 IU of vitamin D plus 1000 mg of calcium per day did not significantly prevent fractures in healthy older women.

These studies add more weight to hints that have been accumulating over the years, that just increasing calcium intake is not necessarily better for health.  Some cultures of the world have very low levels of calcium intake, but very little osteoporosis.  Meanwhile, the US recommendations for daily calcium have climbed over the years, so that now the RDA for women over age 50 is 1200 mg/day.  When it comes to bone health, just adding more calcium is like throwing more bricks on a construction site, and hoping that they’ll form a building.  You also need an architect and foreman — namely, vitamin D and vitamin K.

So how do we parse all this confusion about calcium, health, and disease for older adults?  Here’s my bottom line:

  • Men:  Keep your daily calcium intake under 1000 mg/day.  For most men, this means skipping the calcium supplements altogether.
  • Women:  Ditch the high-dose calcium supplements that provide 1000-1500 mg/day.  Aim for that 600-1000 mg/day range total between dietary and supplemental calcium, with an emphasis on dietary sources (dairy, leafy greens, sardines).
  • Men and women:  Get your blood tested for 25-hydroxyvitamin D on a regular basis; aim for a level between 40-80 ng/ml.  If it is low, you may safely take higher levels of supplemental vitamin D3 (consult your doctor for the right amount — I usually recommend anywhere from 2,000-10,000 IU per day).  If you have CVD, osteoporosis, or risk factors for these conditions, be sure to get extra vitamin K along with vitamin D3.
Stay tuned; like all of nutritional science, the landscape and recommendations are constantly in flux.

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