Associations between a priori-defined dietary patterns and longitudinal changes in bone mineral density in adolescents

Abstract Objective To quantify short- and long-term associations between dietary patterns defined a priori and bone mineral density (BMD) during adolescence. Design Dietary patterns were defined at 13 years old using a Mediterranean diet (MD) quality index, the Dietary Approaches to Stop Hypertension (DASH) diet index and the Oslo Health Study (OHS) dietary index. Linear regression coefficients were used to estimate associations between dietary patterns and forearm BMD at 13 and 17 years, measured by dual-energy X-ray absorptiometry. Setting Public and private schools of Porto, Portugal. Subjects The EPITeen cohort comprising 1180 adolescents born in 1990, recruited at schools during the 2003/2004 school year and re-evaluated in 2007/2008. Results In girls, at 13 years, mean BMD (g/cm2) in the first and third tertiles was 0·369 and 0·368 for the MD pattern, 0·368 and 0·369 for the DASH diet, and 0·370 and 0·363 for the OHS index. In boys, mean BMD (g/cm2) in the first and third tertiles was 0·338 and 0·347 for the MD pattern, 0·342 and 0·346 for the DASH diet, and 0·344 and 0·342 for the OHS index. None of these differences were significant. Mean BMD at 17 years and prospective variation were also not significantly different between tertiles of adherence to each score. However, a trend of increased BMD at 13 years with greater adherence to the MD pattern was observed in boys (adjusted coefficient = 0·248; 95 % CI 0·052, 0·444). Conclusions The selected dietary patterns may not capture truly important dietary differences in determining BMD or diet may not be, beyond nutrient adequacy, a limiting determinant of BMD.