Associations of social and demographic variables with calcium intakes of high school students.

OBJECTIVE: To assess usual calcium intake of urban high school students and to assess the association of social and demographic variables with calcium intake.

DESIGN: A self-administered survey instrument containing the following elements: a food frequency questionnaire (FFQ) developed to estimate calcium intake; questions to elicit demographic information; and scales to reflect taste enjoyment of dairy products, social reinforcement for consumption of milk, perceptions of others' opinions about milk, and behavioral modeling of milk consumption (ie, the frequency of observing friends' and family members' use of milk). The FFQ was shown to include major sources of calcium in diets of a pretest sample (n = 130).

SETTING: Urban high schools in a metropolitan setting.

SUBJECTS/SAMPLES: Students in one class per grade level in six high schools (approximately 900 students) were asked to participate. Of the 856 questionnaires completed, 785 were usable.

MAIN OUTCOME MEASURES: Total calcium intake, as estimated using the FFQ.

STATISTICAL ANALYSES PERFORMED: Descriptive statistics, t tests, one-way analysis of variance, correlation analysis, and stepwise multiple regression analysis were used to assess relationships of independent variables with calcium intake.

RESULTS: Mean estimated calcium intakes for male and female students were 1,146 +/- 41 mg/day (mean +/- standard error of the mean) and 815 +/- 26 mg/day (P < .001), respectively, 59% of which was obtained from milk. Median intakes were 1,016 mg/day for boys and 676 mg/day for girls, and more than half the students had intakes that were below current recommendations. Multiple regression analysis revealed significant predictors of total calcium intake: gender (boys > girls); taste enjoyment of dairy products; number of meals and snacks per day; age; ethnicity (whites > Asians); behavioral modeling of milk consumption; perceptions of others' opinions, recommendations, and use of milk; and soft drink consumption (total adjusted R2 = .304). With the exception of age, these variables were positively associated with calcium intake. Regression equations developed for boys and girls separately revealed that different variables entered the equations.

APPLICATIONS/CONCLUSIONS: Most of the variability in adolescents calcium intakes remained unexplained by the variables included in this study. Nevertheless, the results suggest that education programs focusing on taste enjoyment of dairy products and building on the influence of peers and family members may have a positive impact on calcium intake.