Bone status among postmenopausal women with different habitual caffeine intakes: a longitudinal investigation.

OBJECTIVE: Caffeine consumption has been proposed as a risk factor for bone loss in postmenopausal women. Past epidemiologic studies on caffeine and bone have been confounded by covariates including cigarette and alcohol use, differing levels of physical activity and hormone replacement therapy. The purpose of the study was to use a longitudinal design to determine the relationship between habitual dietary caffeine intake and postmenopausal bone status. METHODS: Data were collected at two time points separated by two years; 138 women with little or no exposure to tobacco or to drugs known to affect bone status were seen at Visit 1, and 112 returned for Visit 2. Ninety-two of these subjects had received no drugs known to affect bone status over the two-year interval and were kept in the sample. Nutrient and caffeine intake were assessed from three-day diet records. Bone measurements were made by dual energy x-ray absorptiometry (DXA). RESULTS: Correlation analyses indicated no association between dietary caffeine intake and total body or femoral neck bone density or bone mass. Similarly, no associations were found between caffeine consumption and longitudinal changes in total body or femoral neck bone measurements. These results held true both with and without statistical adjustment for calcium intake. CONCLUSIONS: This study does not support the idea that caffeine is a risk factor for bone loss in healthy postmenopausal women.

Longitudinal nutrient intake patterns of US 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.

Influences on adolescent eating behavior.

PURPOSE: The food consumption behavior of American adolescents often fails to meet dietary recommendations, indicating the need for investigation of the factors that influence this behavior. This study, guided by Bandura's Social Cognitive Theory, examined relationships between such behavior and other personal, environmental, and behavioral variables. METHODS: A paper-and-pencil instrument was administered to a sample of 242 high school students. "Pyramid," fat, and sugar food scores were calculated to measure subjects' dietary diversity along with their consumption of fats and sugar/sweets. Statistical analyses were conducted to identify relationships between subjects' food scores and other study variables. RESULTS: Male and female subjects' pyramid scores were positively related (p < or = 0.05) to the number of meals they consumed daily. Some gender differences emerged in the data, as conformity to parents, snack consumption, and consumption of meals and snacks from home predicted males' Pyramid scores, while amount of physical exercise predicted pyramid scores of females. Both male and female subjects' fat and sugar scores were positively related (p < or = 0.05) to their consumption of meals and snacks from the school cafeteria and overall snack consumption and negatively related to their self-efficacy for making healthful food choices. Females' fat scores were further predicted by their consumption of fast food. CONCLUSIONS: Different aspects of adolescents' food consumption behavior may be influenced by different factors, which may vary between males and females. Therefore, nutrition and health professionals should tailor educational and treatment strategies according to both the gender of their patients and the specific desired dietary outcomes.