Relation between calcium intake and fat oxidation in adult humans

OBJECTIVE: To determine if total calcium (Ca2+) intake and intake of Ca2+ from dairy sources are related to whole-body fat oxidation. DESIGN: Cross-sectional study. SUBJECTS: A total of 35 (21 m, 14 f) non-obese, healthy adults (means.d., age: 316 y; weight: 71.212.3 kg; BMI: 23.72.9 kg m-2; body fat: 21.45.4%). MEASUREMENTS: Daily (24 h) energy expenditure (EE) and macronutrient oxidation using whole-room indirect calorimetry; habitual Ca2+ intake estimated from analysis of 4-day food records; acute Ca2+ intake estimated from measured food intake during a 24-h stay in a room calorimeter. RESULTS: Acute Ca2+ intake (mg kcal-1) was positively correlated with fat oxidation over 24 h (r=0.38, P=0.03), during sleep (r=0.36, P=0.04), and during light physical activity (r=0.32, P=0.07). Acute Ca2+ intake was inversely correlated with 24-h respiratory quotient (RQ) (r=-0.36, P=0.04) and RQ during sleep (r=-0.31, P=0.07). After adjustment for fat mass, fat-free mass, energy balance, acute fat intake, and habitual fat intake, acute Ca2+ intake explained 10% of the variance in 24-h fat oxidation. Habitual Ca2+ intake was not significantly correlated to fat oxidation or RQ. Total Ca2+ intake and Ca2+ intake from dairy sources were similarly correlated with fat oxidation. In backwards stepwise models, total Ca2+ intake was a stronger predictor of 24 h fat oxidation than dairy Ca2+ intake. CONCLUSION: Higher acute Ca2+ intake is associated with higher rates of whole-body fat oxidation. These effects were apparent over 24 h, during sleep and, to a lesser extent, during light physical activity. Calcium intake from dairy sources was not a more important predictor of fat oxidation than total Ca2+ intake.