A diet high in protein, dairy, and calcium attenuates bone loss over twelve months of weight loss and maintenance relative to a conventional high-carbohydrate diet in adults

Abstract

Weight loss causes bone mineral loss. Higher protein diets continue to be criticized for further potential harmful bone effects, including elevated urinary calcium, but may promote bone health if protein sources include dairy. Overweight middle-aged subjects (n = 130, 59 males) were randomized to a diet providing 1.4 g·kg-1·d-1 protein and 3 daily servings of dairy (PRO) or 0.8 g·kg-1·d-1 protein and 2 daily servings of dairy (CARB) for 4 mo of weight loss plus 8 mo of weight maintenance. Diets prescribed 6276 kJ/d for females and 7113 kJ/d for males. Bone mineral content and density (BMD) for whole body (WB), lumbar spine (LS) and total hip (TH) were measured using dual X-ray absorptiometry, and dietary intake using 3-d weighed food records. Urinary calcium was measured using 24-h collection at 0 and 8 mo for a subsample (n = 42). Participants lost body weight (mean, 95% CI) of 8.2% (7.5-8.9%) at 4 mo, 10.6% (9.5-11.8%) at 8 mo, and 10.5% (8.9-12.0%) at 12 mo without differences between groups at any time (P = 0.64). At 12 mo, PRO BMD was higher by 1.6% (0.3-3.0%) at WB, 2.1% (0.6-3.7%) at LS, and 1.4% (0.2-2.5%) at TH compared with CARB. PRO calcium intake was higher (PRO: 1140 ± 58 mg/d, CARB: 766 ± 46; P < 0.01), as was urinary calcium (PRO: 163 ± 15 mg/d, CARB: 100 ± 9.2; P < 0.01). A reduced-energy diet supplying 1.4 g·kg -1·d-1 protein and 3 dairy servings increased urinary calcium excretion but provided improved calcium intake and attenuated bone loss over 4 mo of weight loss and 8 additional mo of weight maintenance. © 2008 American Society for Nutrition.