Associations Between Biomarker‐Calibrated Protein Intake and Bone Health in the Women's Health Initiative

Abstract

OBJECTIVEThe effects of dietary protein intake on bone health are controversial. This study examined the relation between protein intake with bone mineral density (BMD) and fracture within the Women's Health Initiative (WHI).METHODSThe WHI recruited 161,806 women aged 65–79 into the WHI‐Observational Study (OS) and WHI‐Clinical Trial (CT) between 1993 and 1998. Fractures were collected annually (WHI‐OS) or semi‐annually (WHI‐CT) by questionnaire through 2011. BMD was measured at baseline and 6 years among 10,833 women using dual‐energy x‐ray absorptiometry. Protein and energy intake were assessed via the WHI Food Frequency Questionnaire and calibrated using regression equations established based on biomarkers of protein and energy intake. Cox (fracture) and linear (BMD) regression models were adjusted for confounders including age, race/ethnicity, and body mass index.RESULTSMedian calibrated protein intake was 14% of energy. Women consuming 20% higher calibrated protein were 9% less likely to have a hip fracture (95% CI= 1%‐15%). Each 20% increase in calibrated protein was associated with higher BMD for total body (mean 6‐year change 0.004 g/cm2, 95% CI = 0.001–0.007 g/cm2) and hip (0.003 g/cm2, 95% CI= 0.001–0.005 g/cm2).CONCLUSIONHigher protein intake was associated with reduced risk of hip fracture and better maintenance of BMD over time. These data suggest higher protein intake may be an intervention target for preserving bone health.Funded by NHLBI (WHI) and NIA (4R00AG035002).