Comparison of high protein and normal protein weight loss diets on bone density in overweight post-menopausal women
D. Jesudason1,2 & P. Clifton1,2
Author affiliations
1Commonwealth Scientific and Industrial Research Organisation, Adelaide, SA, Australia; 2University of Adelaide, Adelaide, SA, Australia.
Introduction: The role of dietary protein in maintaining bone health is controversial. Traditionally the acidifying effect of high dietary protein (HP) has been thought to promote calcium loss from bone and hence hypercalciuria and so was considered harmful compared to a normal protein (NP) diet. However more recently the anabolic effect of increased dietary protein and its effect in increasing calcium absorption have been appreciated. There are no long term prospective clinical trials comparing high and normal protein diets in maintaining bone health.
Methods: We randomized 323 overweight (BMI > 27 kg/m2) post-menopausal women aged 40-70 to an isocaloric HP (approximately 100 g/day) or NP (approximately 67 g/day) weight loss diet for 2 years. We had excluded subjects with impaired bone health eg primary hyperparathyroidism, vitamin D insufficiency, previous low impact fracture, hip t score < −2.0 or using medications such as hormone replacements or steroids.
Results: Subjects were equally matched for age, weight, serum parathyroid hormone, vitamin D, cross-laps and osteocalcin at baseline. 69 of 164 HP subjects and 68 of 159 NP subjects completed the 2 year study. As expected there was matched weight loss across both groups with the HP group losing 9.6±1.6 kg vs NP 10.3±1.9 kg (NS). There was no significant difference in bone loss after 2 years at either hip, forearm or spine between groups (Table 1). ANCOVA analysis showed baseline bone density at any site and to a lesser extent baseline Vitamin D was the only significant predictors of bone density at that site at 2 years. Baseline weight, parathyroid hormone, cross-laps and 24 hour urea were not significant predictors.
Conclusion: The amount of dietary protein does not significantly affect bone health in post-menopausal women.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however funding details are unavailable.