W1003: Parent and household influences on calcium intake among preadolescents
Statement of Issues and Justification
"Calcium crisis affects American youth" was the headline for a December 10, 2001, news release from the National Institute of Child Health and Human Development. Data from the USDA's Continuing Survey of Food Intakes by Individuals for 1994-96 and 1998 (CSFII 1994-96 and 1998) estimated the mean calcium intake of girls aged 6-11 years to be 865 mg per day, whereas girls aged 12-19 years were consuming an average of 773 mg per day [1]. These averages are well below the 1300 mg Adequate Intake (AI) level for calcium set by the Institute of Medicine for girls and boys 9 through 18 years [2]. Usually boys consume more calcium than girls, however the average intakes for boys documented by the CSFII 1994-96 and 1998 surveys were 984 mg among 6-11 year olds and 1,145 among 12-19 year olds both well below the AI [1]. One of the major lines of evidence to establish the AI in this age group was calcium retention to meet peak bone mineral accretion.Obtaining sufficient calcium during adolescence helps ensure adequate mineralization of the skeleton to ensure bone health later in life. Research has suggested that peak bone density can occur as early as age 16 for the hip and the early mid-twenties for other bones [3]. Thus, during this time of maximum bone accretion, the youth of America are not consuming sufficient calcium to reach peak bone mass - potentially leaving themselves vulnerable to osteoporosis later in life. Osteoporosis has been described as a "pediatric disease that manifests itself in old age" [4]. Maintaining a high peak bone mass has been shown to not only prevent fracture in the postmenopausal years, but also during adolescence [5]. Adolescents are physiologically able to absorb and retain more calcium than children and young adults [6]. However, the extent to which this ability can be used to an adolescent's advantage is dependent on the level of calcium intake.
Osteoporosis is the most readily identifiable health issue associated with inadequate calcium intake. Osteoporosis is responsible for more than 1.5 million fractures annually [7]. The health care costs associated with osteoporosis are significant and estimated at $13.8 billion per year for osteoporotic-related fractures alone. One in three women and one in eight men aged 50 years and older will experience an osteoporotic-related fracture in their lifetime [8]. An average of 24% of hip fracture patients aged 50 years and older die in the year following fracture and hip fracture is more likely than heart attack, stroke, and/or cancer to lead to functional impairment [9].
Osteoporosis is a major public health problem [10] that affects every gender, race and economic group though white females are at highest risk [11-13]. The National Osteoporosis Risk Assessment [14], a longitudinal observational study of 200,160 ambulatory postmenopausal women aged 50 years or older, found that Asian or Hispanic heritage was associated with a significantly increased likelihood of osteoporosis. On the other hand, African American heritage significantly decreased the likelihood.
In addition to osteoporosis, research suggests there may be other negative health consequences associated with an inadequate calcium intake. Davies, et al. suggest that maintaining a high calcium intake while dieting (contrary to popular dieting notions) may help an individual lose or control their weight [15]. Research has also noted a relationship between calcium intake and blood pressure in adolescents. A study of 180 Hispanic and African American teenagers (14-16 years of age) whose diets were low in calcium, potassium, magnesium and several vitamins had higher blood pressure than those with more adequate diets. The comparison is made between the diets of these teens and the DASH trial that has highlighted the value of dairy products in controlling high blood pressure (dairy products provide calcium, magnesium, and potassium) [16].
Calcium intake depends, in large part, upon an intake of dairy foods and hence the Food Guide Pyramid [17] recommends that older children and teenagers, consume 3 servings/day from the milk, yogurt and cheese food group. However, data from the CSFII 1996 indicate that for the age group 12-19 the average number of dairy servings consumed by males was 1.7, and 1.6 for females [18]. This is approximately 50% of the recommendation. From a survey of 4,746 children aged 11-18 years [19], only 29.5% of the girls and 42.5% of the boys met the recommended intake for calcium (Healthy People 2010 target=75%). No socioeconomic (SES) group met the 2010 target, however there was a significant test for trend (p=.001) ranging from 37.6% among the high SES group to 22.3% among the low SES group.
Data from the third National Health and Nutrition Examination Survey (NHANES III) support the observations that calcium intake is less than desirable [20]. NHANES III data used complete and reliable 24 hour recalls for 29,105 persons aged 2 months and older and estimated calcium intakes among two minority groups: non-Hispanic Blacks (n=8,391) and Mexican Americans (n=8,419), as well as non-Hispanic whites (n=10,533). Data indicate that for all age groups, including adolescence, males consumed higher amounts of calcium than their female age counterparts. In males, calcium intake peaked at adolescence and then declined in early adulthood. For females, the calcium intake peaked during childhood and began to decline in adolescence. For females, the average daily intake fell below the AI recommendation in all three ethnic groups beginning at the adolescent period [20]. Unfortunately, data from the NHANES III were considered "statistically unreliable" for Asians due to small sample size. This pattern of low calcium intake persists even though the National Dairy Council has, over the past decade, mounted a vigorous, aggressive media campaign to increase calcium intake.
Multiple and diverse factors are working against achievement of adequate calcium nutrition in preadolescents and adolescents. It has been suggested that some of these factors include (1) displacement of milk as a fluid with soda, juices and sports drinks [21-23]; (2) the perception, particularly among females that milk and/or dairy products are fattening and therefore intake is restricted or eliminated; (3) milk intolerance; and (4) psychosocial developmental changes. At the same time, it is clear that some factors are also working to ensure at least a minimal intake of calcium such as consumption of milk by other family members, parental expectations that milk will be consumed regularly, and availability of calcium-rich foods in the home [24].
Familial factors play an important role in the calcium intake of youth [25], thus a clearer understanding of parental factors such as knowledge, attitudes, behaviors, and environment and their influence on calcium intake of preadolescents is needed. This project will examine these factors and how they relate to the child's intake of calcium-rich foods, knowledge, attitudes, and behaviors. A clearer understanding of familial factors and how they influence preadolescent calcium intake will enable intervention strategies to be more effective. Additionally little information is available on the role of dietary supplements and fortified foods, which are new to the food supply, and the contribution of these items to the calcium intake of children and adolescents. This project will examine these factors with special attention paid to gender and with a focus on the ethnic groups at highest risk for osteoporosis (Asians, Hispanics, and whites).
Evidence suggests that dietary behavior is established in childhood [26,27]. Food habits and physical activity habits formed early in life have the potential to continue throughout adulthood [26,28]. The Child and Adolescent Trial for Cardiovascular Health (CATCH) demonstrated maintenance of health behaviors following a school-level intervention [29]. This cardiovascular program, targeting eating behaviors, physical activity, and smoking was introduced in the third grade and continued through the fifth grade, and then conducted a three-year follow-up. Students in the intervention schools had significantly lower total fat, saturated fat, and sodium intakes compared to students in the control schools three years following the program [29]. These results indicate that health behaviors that are initiated at a young age can be maintained through adolescence and young adulthood and possibly provide a protective effect later in life. There is no evidence to suggest that dietary behaviors related to calcium would differ from those related to dietary fat and sodium. Thus, research indicates that intervention at younger ages is effective.
Building on information obtained from preadolescents and adolescents in the W191 Multistate Research Project (W191 project), this new proposal will focus on parental and household factors and their influence on calcium intake of preadolescent children (11-12 years old). This age group was selected to provide information helpful in preventing the decline in calcium consumption observed after this age. While information about influences on calcium intake has been gathered from children, parental viewpoints have not been examined. Factors to be addressed in this new proposal include availability of calcium-rich foods in the home, parental consumption of calcium-rich foods at home and away from home, actual or perceived lactose intolerance, belief that dairy products contribute to excess body weight, the presence of hectic day-to-day schedules, food preferences and dislikes, parental expectations regarding calcium-rich food consumption, parental knowledge regarding calcium needs of their child and what foods in what quantities meet calcium needs, attitudes toward use of supplements and calcium-rich foods, parenting skills, and the family eating environment.
Industry has expressed concern about the lack of information about consumption of calcium supplements and calcium fortified food products. A consortium that includes organizations both within the federal research community (NIH, USDA, the Food and Drug Administration, and the Centers for Disease Control and Prevention) and outside it identified that the use of dietary supplements in children (infancy through adolescence) is increasing [30]. However, little is known about supplements for use by children. Further, this group noted that more information was needed concerning "Knowledge and attitudes of caregivers/parents and how they are developed need to be evaluated to determine the impact of such environmental factors on dietary supplement use by children". This proposal will address these concerns of stakeholders.
A promising intervention program to improve calcium intake in preadolescents is currently being launched using the information gained from the W191 project with funding from the Initiative for Future Agriculture and Food Systems (IFAFS) of the USDA [31]. The intervention program is being directed to children through their schools and youth organization activities. The IFAFS research team wanted to include a family or parent component in the intervention plan, however due to the lack of information concerning the parents' perspective regarding their role in the calcium intake of their children, the research team did not include such a plan. This current proposal intends to fill this gap concerning parents, thus allowing intervention programs to achieve even better success. The W191 project and IFAFS project are multistate projects. The three ethnic groups most at risk for osteoporosis are accessible in participating states. In addition, multiple sites allow results to be generalized to the American population representing these ethnic groups.
In summary, national data indicate that the average calcium intake among adolescents is less than desirable during a period when the greatest amount of bone accumulation is occurring. Although some programs have been initiated to redirect the trend in calcium intake, interventions that involve parents would likely enhance the outcomes of these newly developed programs. According to the Healthy People 2010 Objectives Report, 46% of persons age two years and older were at or above the calcium recommendations at baseline measurement and the target for 2010 is 75%. Therefore, the goal of this proposal will help improve the chances of our nation reaching the national objectives regarding calcium intake.
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