Meat Protein and Calcium: Do They Interact Synergistically or Antagonistically?

This study tests the effects of dietary protein and calcium on calcium retention and indices of bone metabolism. It is a controlled feeding trial with a randomized crossover design (2x2 Factorial), studying 34 healthy post-menopausal women. The women are blocked on Body Mass Index (weight in kilograms divided by height in meters squared)and randomly assigned to a high calcium (HC,1500 milligrams per day) or low calcium (LC, 600 milligrams per day) group, and consume both low protein (LP,10% protein) and high protein (HP, 20% protein) diets for 7 weeks each. There is a 3-week "washout" between dietary periods, during which the subjects consume self-selected diets. After 3 week equilibration to each diet, the 2-day rotating menu is extrinsically labeled with a Calcium-47 radiotracer and retention is monitored for 28 days by whole body scintillation counting. In addition to Calcium retention, other endpoints include urinary indices of acid excretion and urine serum indices of bone resorption.