Is protein intake associated with bone mineral density in young women?

Abstract

BackgroundThe range of protein intake for optimizing bone health among pre‐menopausal women is unclear.ObjectiveTo examine cross‐sectional and longitudinal associations between baseline dietary protein and bone mineral density (BMD) among 560 women aged 14–40.MethodsDietary protein intake was assessed using a semi‐quantitative food frequency questionnaire in participants enrolled in a study investigating associations between contraceptive use and bone health. Annual change in hip, spine, and whole body BMD were measured using dual‐energy X‐ray absorptiometry. Cross‐sectional and longitudinal associations between baseline protein intake (%kcal) and BMD were examined using linear regression analysis and generalized estimating equations adjusted for confounders.ResultsBaseline mean (±SD) protein intake was 15.5%±3.2% kcal. After multi‐variable adjustment, mean BMD was similar across each tertile of protein intake. In cross‐sectional analyses, low vegetable protein intake was associated with lower BMD (p=0.03 for hip, p=0.10 for spine, p=0.04 for whole body). For every percent increase in protein(%kcal), there were no significant longitudinal changes in BMD at any anatomic site.ConclusionData from this longitudinal study suggest higher protein intake does not have an adverse impact on bone in pre‐menopausal women. Cross‐sectional analyses suggest low vegetable protein intake is associated with lower BMD. This study was funded by R01 HD31165‐01, R01 HD31165‐08 and T32‐AG027677.