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Calcium Requirements May Be OverestimatedBy 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 Curtiss Hunt with statistician LuAnn Johnson, both based at the agency's Grand Forks Human Nutrition Research Center (GRHNRC) 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 or older.
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 volunteers—415 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.