Research Article
Calcium and Dairy Intake: Longitudinal Trends during the Transition to Young Adulthood and Correlates of Calcium Intake

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Abstract

Objective

To describe changes in calcium and dairy intake during the transition from middle adolescence to young adulthood and to identify baseline correlates of calcium intake in young adulthood.

Design

Population-based, 5-year follow-up study (Project EAT: Eating Among Teens).

Setting

Baseline surveys were completed in Minneapolis/St. Paul, MN schools and by mail at follow-up.

Participants

Males and females (N = 1521) attending high school at baseline (mean age = 15.9 years) and with a mean age of 20.5 years at follow-up.

Main Outcome Measures

Calcium intake.

Analysis

Mixed and linear regression methods were used to respectively examine trends and correlates of intake.

Results

During the transition to young adulthood, mean daily calcium intakes of females and males decreased by an average of 153 mg and 194 mg respectively. Mealtime milk availability, health/nutrition attitudes, taste preference for milk, healthful weight control behaviors, and peer support for healthful eating at baseline were associated with better follow-up calcium intake. Time spent watching television and lactose intolerance were associated with lower intake at follow-up.

Conclusions and Implications

Nutrition interventions are needed to counter longitudinal decreases in calcium intake. Interventions targeted to adolescents should address the availability of milk at meals and other identified supports for healthful eating.

Introduction

Calcium and dairy products play major roles in the maintenance of health and the prevention of chronic disease.1 Peak bone mass is not achieved until the third decade of life; therefore, adequate intake of calcium and other essential nutrients found in dairy products (eg, protein, vitamin D) are important during young adulthood to support health and prevent osteoporosis.2, 3 National survey data indicate only about half (53%) of young men and a mere 21% of young women (19 to 30 years) in the United States consume the recommended amount of calcium.4 Furthermore, 39% of men and 43% of women (20 to 29 years) consume less than even 1 daily serving of dairy products.5

Designing effective interventions to improve calcium consumption will require knowledge of longitudinal trends in dietary intake during the transition from adolescence to adulthood and a strong understanding of what factors during adolescence may have an influence on intake as young people progress to adulthood. Little prior research could be found describing changes in diet during this period, and only a small number of mostly cross-sectional studies have identified correlates of calcium intake (eg, male gender, on-campus residence, food preparation involvement) during early young adulthood.6, 7, 8, 9

The current study aimed to describe longitudinal changes in intakes of calcium and dairy products during the transition to young adulthood in a large ethnically and socioeconomically diverse sample of young people in Minnesota. In addition, this study aimed to identify baseline correlates of follow-up calcium intake from within the personal, behavioral, and socioenvironmental domains described by Social Cognitive Theory (SCT).10

Section snippets

Sample and Study Design

Data for the current study were drawn from Project EAT (Eating Among Teens), a prospective, population-based study designed to examine determinants of dietary intake and weight status. The sample consisted of 1521 young adults (45% male) who completed study assessments at baseline and follow-up. The mean age of participants was 15.9 years (SD = 0.8 years) at baseline and 20.5 years (SD = 0.8 years) at follow-up.

For Project EAT-I (1998-1999), 3074 Minnesota students completed the Project EAT

Longitudinal Trends in Intake of Calcium and Dairy

During the transition from middle adolescence (baseline) to young adulthood (follow-up), mean daily intakes of calcium and dairy products decreased in terms of absolute intake (Table 1) and intake density (ie, intake per 1000 kcal; data not shown). Females and males respectively reduced their daily calcium intakes by an average of 153 ± 19 mg and 194 ± 23 mg. Although 38% of females and 39% of males increased their intake of calcium over 5 years, the majority of the sample reduced their intake

Discussion

This study found longitudinal decreases in daily intakes of calcium, total dairy servings, and milk servings during the transition from adolescence to young adulthood. In early young adulthood, two-thirds of females and more than half of males had calcium intakes that were lower than recommended. The findings of this study and others suggest there is a need for interventions to address dietary calcium intake prior to and during the transition from adolescence to adulthood.4, 34, 35, 36 The

Implications for Research and Practice

Additional research will be needed to add to the correlates of intake identified in this study and to determine which factors are the strongest and most proximal influences on calcium intake during early young adulthood. Similar to other research studies that have investigated correlates of dairy or calcium intake, this study was able to explain only a small proportion of the total variance in calcium intake among young women (31%) and men (29%) at follow-up.34, 39, 40 More total variance might

Acknowledgments

Data collection was supported by grant number R40 MC 00319 (PI: D. Neumark-Sztainer) from the Maternal and Child Health Bureau (Title V, Social Security Act), Health Resources and Service Administration, Department of Health and Human Services. Analyses were supported by the Adolescent Health Protection Program, grant T01-DP000112 (PI: L. Bearinger) from the Centers for Disease Control and Prevention (CDC), Department of Health and Human Services. The content of the manuscript is solely the

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    Data collection was supported by grant number R40 MC 00319 (PI: D. Neumark-Sztainer) from the Maternal and Child Health Bureau (Title V, Social Security Act), Health Resources and Service Administration, Department of Health and Human Services. Analyses were supported by the Adolescent Health Protection Program, grant T01-DP000112 (PI: L. Bearinger) from the Centers for Disease Control and Prevention (CDC), Department of Health and Human Services.

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