Extra Calcium Not Always Extra Beneficial for Bones


Its important to get enough calcium for your bones, but a new Swedish study suggests more than that may not do much extra good. The study found that women with the lowest initial dietary intake of calcium were 18% more likely to suffer a fracture over the next 19 years. But there was little difference in fracture risk between women in the middle levels of calcium intake and those getting the most.

These findings re-enforce the advice to make sure to get adequate calcium from food, but dont overdo it with supplements, says Bess Dawson-Hughes, MD, director of Tufts HNRCA Bone Metabolism Laboratory. Then make sure youre getting enough vitamin D, so your body can utilize that calcium.

The latest guidelines from the Institute of Medicine, updated last November, advise women over 50 and men over 70 to get 1,200 milligrams of calcium daily. Younger adults should aim for 1,000 milligrams daily. The updated vitamin D recommendations call for 600 IU of vitamin D daily through age 70, while older adults need 800 IU. Some expert groups have called for higher vitamin D intakes for those at risk of deficiency.

Eva Warensj, PhD, of Uppsala University and colleagues looked at data on 61,433 women in the Swedish Mammography Cohort, whose ages when the study began ranged from 40 to 80. They compared responses to a food questionnaire completed at the studys start in 1997 with subsequent bone-fracture rates. Between 2003 and 2009, researchers also asked a subgroup of 5,022 participants to have x-ray absorptiometry scanning for osteoporosis, to give blood and urine samples, and to fill out an additional food questionnaire.

During an average 19 years of followup among the entire cohort, 24% of the women suffered a first fracture. Among the x-ray subgroup, 20% developed osteoporosis.

Dividing the women into five groups (quintiles) ranked by calcium intake, Warensj and colleagues found that fracture risk was indeed greatest in those with the lowest calcium. That quintile, with calcium intake below 751 milligrams daily, had a risk of 17.2 first fractures per 1,000 person-years. Compared to the middle calcium quintile, used as a reference group, that worked out to an 18% greater risk.

But there was little difference in fracture risk among the second-lowest to highest quintiles of calcium intake-14.7, 14.0, 14.1 and 14.0, respectively. The top level of calcium intake was more than 1,137 milligrams daily.

A slightly different pattern was seen for osteoporosis risk in the subcohort that underwent x-ray scanning. There, the lowest-calcium quintile was at 47% greater risk of osteoporosis than the reference group. But the women with the most calcium did see a benefit compared with those in the middle, a 16% reduced incidence of osteoporosis. The second, third and fourth quintiles, however, did not vary significantly in osteoporosis risk.

Warensj and colleagues said the results suggested that public-health efforts ought to concentrate on improving the calcium intake of those at greatest risk, rather than increasing the intake of those already consuming satisfactory amounts.

TO LEARN MORE: BMJ, online before print; abstract at dx.doi.org/10.1136/bmj.d1473.


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