Effects of various forms of calcium on body weight and bone turnover markers in women participating in a weight loss program

Objective: This study examined the effects of calcium intake on body weight, body fat, and markers of bone turnover in pre-menopausal adult women undergoing a 12 week weight loss program of diet and exercise. Methods: Subjects were prescribed a 12 week diet with a 500 Kcal restriction containing about 750 mg calcium/day, exercised 3 times/week, and were given either placebo capsules, capsules of calcium lactate or 14 calcium phosphate (daily dose about 800 mg calcium), or low fat milk (daily dose about 800 mg calcium). Subjects completed and returned daily diet diaries weekly. Results: Daily calcium intake in mg from diet records + supplement assignment was: 788 1 +/- 175 (placebo), 1698 +/- 210 (Ca lactate), 1566 +/- 250 (Ca phosphate), 1514 +/- 225 (milk)(no significant differences among the calcium and milk groups). Each group had statistically significant changes in body weight (p < 0.01), but there were no significant differences among groups for the weight loss: 5.8 +/- 0.8 kg (placebo), 4.1 +/- 0.7 kg (Ca lactate), 5.4 +/- 1.3 kg (Ca phosphate), 4.2 +/- 0.8 kg (milk). Body fat was changed significantly in each group (p < 0.01), with milk group showing a little less change than the other groups. Serum bone specific alkaline phophatase activity, a bone synthesis marker, increased similarly in all groups (p < 0.001 within groups, no significance for changes among groups). In contrast, the Ca lactate group, but not other groups, had a drop in urine values for alpha helical peptide, a bone resorption marker (p < 0.05). Conclusion: For the conditions of this study, increased calcium intake, by supplement or milk, did not enhance loss of body weight or fat, though calcium lactate supplementation lowered values for a marker of bone degradation.