Fat oxidation and its relation to serum parathyroid hormone in young women enrolled in a 1-y dairy calcium intervention

Abstract

Increased dietary calcium is associated with changes in body composition. One proposed mechanism is that dietary calcium increases fat oxidation, potentially via regulation of serum parathyroid hormone (PTH) concentrations. The objectives of the study were to determine whether acute or chronic increased dairy calcium intakes alter postprandial whole-body fat oxidation and whether the increased intake is related to changes in PTH concentrations. Normal-weight women aged 18-30 y were randomly assigned to a low (<800 mg/d, control; n = 10) or high (1000-1400 mg/d; n = 9) dietary calcium intake group for 1 y. Whole-body fat oxidation was assessed by measuring respiratory gas exchange after each subject consumed 2 isocaloric liquid meals containing 100 or 500 mg Ca at baseline and 1 y. Fasting serum PTH was measured at baseline and 1 y. The mean 1-y change in fat oxidation was higher in the high-calcium group than in the low-calcium control group after a low-calcium meal (0.10 +/- 0.05 compared with 0.005 +/- 0.04 g/min; P < 0.001) and a high-calcium meal (0.06 +/- 0.05 compared with 0.03 +/- 0.04 g/min; P < 0.05). The 1-y change in serum log PTH was negatively associated with the 1-y change in postprandial fat oxidation after a high-calcium meal (partial r = -0.46, P < 0.04) when controlled for the1-y change in total body fat mass. The results suggest that a chronic diet high in dairy calcium increases whole-body fat oxidation from a meal, and increases in fasting serum PTH relate to decreases in postprandial whole-body fat oxidation.