Increased Calcium Intake May Lead to Phosphorus Deficiency

OMAHA, Neb.--Increasing calcium intake without increasing phosphorus consumption could prove detrimental to bone health, according to scientists from Creighton University, in cooperation with researchers from the Institute of Medical and Veterinary Science in Adelaide, South Australia. Their study, published in the June issue of the Journal of the American College of Nutrition (21, 3:239-44, 2002) (www.am-coll-nutr.org), involved two data sets: 1) 543 studies of healthy women (aged 35 to 65) and 2) 93 studies of men and women (aged 19 to 78).

Analysis indicated that fecal calcium and dietary phosphorus were positively and independently associated with fecal phosphorus, explaining 73 percent of the variance in fecal phosphorus in data set one and 33 percent of the variance in data set two. Researchers noted that each .5 g increase in calcium intake decreased phosphorus absorption by .166 g, leading to the potential for phosphorus deficiency to develop.

"Our study found that increasing the amount of calcium consumed without increasing phosphorus intake will lower phosphorus absorption," Robert P. Heaney, M.D., lead researcher from Creighton University, said in a release from the National Fluid Milk Processor Promotion Board. "Unless your intake of phosphorus is generous, the ratio of calcium to phosphorus is very important to ensure that you get enough of bone minerals, and this is particularly critical for older adults receiving treatment for osteoporosis."

Researchers suggested that intakes with a high ratio of calcium to phosphorus can occur with the use of supplements and fortified foods consisting of non-phosphate calcium salts.

Currently, the recommended daily allowance (RDA) for phosphorus, which is found in good amounts in dairy, meat and fish, is 700 mg, and the RDA for calcium is 1,000 mg.

"Phosphorus is required to merge calcium into bone," said Machelle Seibel, M.D., medical director for Waltham, Mass.-based Inverness Medical Innovations Inc., manufacturer of Posture-D®, which contains calcium phosphate. "This typically takes place in the intestinal tract. Without enough phosphorus in their systems, the millions of American women taking over-the-counter calcium supplements may be robbing their bodies' natural store of phosphorus in order to digest the calcium they take."