Calcium Requirements May Be Overestimated
By Rosalie Marion
Bliss December 6, 2007
People who want healthy bones have long been told to get plenty of
calcium. After all, the body compensates for an inadequate calcium intake by
drawing calcium out of bones and putting it into the blood stream. Now,
Agricultural Research Service (ARS)
scientists have reported study findings that suggest calcium's current
recommended amount, called "adequate intake" or AI, for American adults aged 19
or older may be greater than necessary.
The study was led by ARS biologist
Hunt with statistician
Johnson, both based at the agency's Grand Forks Human Nutrition Research
in Grand Forks, ND. Hunt is trying to fill in knowledge gaps about calcium's
estimated average requirement for adults. Today's AI for calcium is 1,000 mg
per day for those aged 19 to 50 years, and 1,200 mg per day for those aged 51
The findings were published recently in the American Journal of Clinical Nutrition. ARS
is the U.S. Department of Agriculture's
chief scientific research agency.
The body's skeleton needs adequate dietary calcium to reach its full
potential in terms of bone mass. Yet calcium alone does not protect against
bone loss, especially during menopause.
The researchers analyzed data collected from 155 male and female
volunteers, aged 19 to 75 years, who participated in at least one in a series
of 19 controlled feeding studies conducted at the GFHNRC. The modeling of those
data suggests that the average amount of dietary calcium needed to maintain a
neutral calcium balance is about 741 mg per day. Calcium balance is the
condition wherein the amount of calcium consumed equals the amount of calcium
lost through elimination.
The body tries to maintain a relatively stable amount of calcium
within a broad range of typical daily calcium intakes fed to
volunteers415 mg on the low end to 1,740 mg on the high end. When fed the
lower amounts, for example, the body was more efficient in keeping calcium.
When fed the higher amounts, the extra calcium was simply eliminated.
The work is of interest to researchers and to nutrition experts who
update nutrient intake recommendations for must-have nutrients.