Longitudinal nutrient intake patterns of U.S. adolescent women: The Penn State Young Women's Health Study

Purpose: To use longitudinal nutrient intake data to determine whether dietary patterns remain consistent (or 'track') as U.S. females progress from age 12 to 18 years. Methods: Three-day diet records were collected at regular intervals over 6 years from participants in the Penn State Young Women's Health Study. Eighty-one subjects remained in the cohort during the study period. Tracking in body weight, in dietary intake of fat, sugar, iron, vitamin C, and in a total dietary score (TDS) was assessed using quartile-ranking analysis, year-to-year Pearson correlation analysis, and longitudinal linear analysis. Results: Rank analysis revealed that subjects maintained their relative quartile positions for body weight throughout the study period, and year-to-year correlation coefficients for this variable were .93-.94. In contrast, rank and correlation analyses showed that the subjects did not track strongly with respect to any nutrient variable. Age 12 to 18 years correlation coefficients ranged from r = .04 for fat intake to r = .15 for the TDS. In longitudinal linear models, slopes differed in direction and significance across the original quartiles for nutrient intake, indicating varying dietary trends over time within the study population. Conclusions: Nutrient intake patterns do not track strongly throughout adolescence among U.S. females. (C) Society for Adolescent Medicine, 2000.