title: Evaluation of an inexpensive calcium absorption index in healthy older men and women.
abstract: OBJECTIVE
  Calcium absorption is an important determinant of calcium retention and bone metabolism. However, most methods of measuring calcium absorption, including the well-established dual stable isotope method, are costly and cumbersome to implement. We evaluated whether an oral calcium tolerance test (OCTT), which involves measuring calcium excretion in a fasting 2-h urine collection and two 2-h collections following an oral calcium dose, may be a useful index of calcium absorption in older adults consuming a fixed calcium intake of 30 mmol/day.
  
  
  METHODS
  After a 10-day metabolic diet containing 30 mmol/day of calcium, subjects had calcium absorption measured using the dual stable isotope method and the OCTT.
  
  
  METHODS
  Eleven healthy subjects aged 54-74 years.
  
  
  METHODS
  Fractional calcium absorption (FCA), calcium excretion in a fasting 2-h urine collection and two 2-h collections in response to a 10-mmol calcium dose (total intake 30 mmol/day).
  
  
  RESULTS
  Calcium excretion from several combinations of the urine collections was examined in relation to FCA. The most predictive of FCA was calcium excretion 4 h following the calcium dose. This measure was significantly correlated with FCA (r = 0.735, P = 0.010), fitting 54% of the variability in FCA.
  
  
  CONCLUSIONS
  Urinary calcium excretion during the 4 h after a 10-mmol calcium dose is a useful index of calcium absorption among older adults consuming recommended calcium intakes. This test is inexpensive, easy to implement and potentially useful in large clinical studies.
authors.affiliation: Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA. lisa.ceglia@tufts.edu
authors.forename: Lisa
authors.initials: L
authors.lastname: Ceglia
authors.forename: Steven A
authors.initials: SA
authors.lastname: Abrams
authors.forename: Susan S
authors.initials: SS
authors.lastname: Harris
authors.forename: Helen M
authors.initials: HM
authors.lastname: Rasmussen
authors.forename: Gerard E
authors.initials: GE
authors.lastname: Dallal
authors.forename: Bess
authors.initials: B
authors.lastname: Dawson-Hughes