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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth 2 Nutrition-Related Health Concerns, Dietary Intakes, and Eating Behaviors of Children and Adolescents INTRODUCTION Good nutrition during childhood and adolescence is essential for growth and development, health and well-being, and the prevention of some chronic diseases. Yet many American children’s diets fall considerably short of recommended dietary standards. Furthermore, poor diet and physical inactivity, resulting in an energy imbalance, are the most important factors contributing to the increase in obesity in childhood. Obesity is the most pressing challenge to nutritional health in this first decade of the 21st century (CDC, 1999). The major nutrition issues among children and adolescents have shifted from nutrient deficiency diseases, common in the first half of the 20th century, to concerns today about overconsumption, poor dietary quality, and food choices. However, food insecurity remains a concern among the poor (Briefel and Johnson, 2004). This chapter provides an overview on nutrition-related health concerns, current dietary and nutrient intakes, and dietary trends over the past 20–40 years for children and adolescents. Importance of Healthful Dietary Behaviors in School-Age Children and Adolescents During childhood and adolescence, good nutrition and dietary behaviors are important to achieve full growth potential and appropriate body composition, to promote health and well-being, and to reduce the risk of
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth chronic diseases in adulthood. Children require sufficient energy, protein, and other nutrients for growth as well as maintenance of body functions. Nutrient needs tend to parallel rates of growth. Growth continues at a steady rate during childhood, then accelerates during adolescence, creating increases in nutrient needs to support the rapid growth rate and increase in lean body mass and body size (Story et al., 2002a). During puberty, adolescents achieve the final 15 to 20 percent of stature, gain 50 percent of adult body weight, and accumulate up to 40 percent of skeletal mass (Story et al., 2002a). Inadequate intakes of energy, protein, or certain micronutrients will be reflected in slow growth rates, delayed sexual maturation, inadequate bone mass, and low body reserves of micronutrients (Story et al., 2002a). In addition to the impact on growth and development, children’s diets are important to ensure overall health and well-being. Dietary practices of children and adolescents affect their risk for a number of health problems, including obesity, iron deficiency, and dental caries. Inadequate nutrition also lowers resistance to infectious disease, and may adversely affect the ability to function at peak mental and physical ability. Obesity in children and adolescents is associated with a number of immediate health risks, such as high blood pressure, type 2 diabetes (T2D), metabolic syndrome, sleep disturbances, orthopedic problems, and psychosocial problems (Daniels, 2006; IOM, 2005b). Furthermore, obese adolescents are likely to remain overweight as adults (IOM, 2005b). Indeed, longitudinal epidemiological studies provide evidence that obesity, hypercholesterolemia, and hypertension track from childhood into adulthood and lifestyle choices such as diet and excess caloric intake influence these conditions (Gidding et al., 2005). There is concern about long-term health as certain dietary patterns, developed in childhood and carried into adulthood, result in an increased risk for chronic diseases, such as obesity, heart disease, osteoporosis, and some types of cancer later in life. Some of the physiological processes that lead to diet-related chronic diseases have their onset during childhood. For example, studies indicate that the process of atherosclerosis begins in childhood (Gidding et al., 2005). Nutritional factors contribute significantly to the burden of preventable illnesses and premature deaths in the United States (DHHS, 2000). Four of the ten leading causes of death in adults are diet related: diabetes, coronary heart disease (CHD), certain cancers, and strokes. Diet is also associated with osteoporosis. Dietary factors also contribute to reproductive health, e.g., adequate consumption of folic acid to prevent neural tube defects in infants. Dietary patterns are influenced by behavioral choices and environmental factors. It may be easier to change children’s health behavior than adults’ behavior. Childhood offers the opportunity to provide the solid foundation needed for healthful lifelong eating patterns. The importance of applying
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth a life-course approach, starting early in life, to the prevention of chronic diseases and obesity has also been emphasized (WHO, 2003). A principal goal of public health is to give people the best chance to enjoy a long and healthy life. Children represent the nation’s present and its future. OVERVIEW OF CHILDREN’S NUTRITION-RELATED HEALTH CONCERNS The rising rate of obesity in children has become a major health concern, both because of its impact on childhood health and its potential effect on the development of chronic disease in adulthood. Obesity status is usually indicated by the body mass index (BMI), which is a measure in which weight is adjusted for height. More specifically, BMI is defined as weight in kilograms divided by height in meters squared. For adults, weight status is based on the absolute BMI level, and in children BMI percentile. BMI measurements in children adjust the children’s weight and stature by their age and gender. In this report, the term “obesity” is used to refer to children and adolescents who have a BMI at or above the age and sex-specific 95th percentile of the BMI charts developed by the Centers for Disease Control and Prevention (CDC) in 2000. Those children and adolescents who have a BMI between the 85th and 95th percentile for age and sex are termed at risk for obesity. In most children and youth, a BMI level at or above the 95th percentile indicates elevated body fat and reflects the presence or risk of related chronic disease (IOM, 2005b, 2007). Trends in Childhood Obesity Childhood obesity has been increasing steadily, particularly during the past two decades. The number of children above the 95th percentile of weight for height has tripled among those in the age bracket of 12 to 19 years, rising from 5 percent in 1976–80 to 17 at present (Ogden et al., 2002, 2006). The National Health and Nutrition Examination Survey (NHANES) III (1988–1994) found an increase from 7 to 11 percent in obesity for 6- to 11-year-old children, compared to NHANES II a decade earlier (1976–1980) (Ogden et al., 2002). Further NHANES survey data (1999–2004) confirmed the continued rise in obesity. Another 15 percent of children and adolescents are estimated to be at risk for obesity (85th to 95th percentile), making a third of children and adolescents obese or at-risk for obesity (Ogden et al., 2002, 2006). These trends are shown in Figure 2-1. Although childhood obesity has increased in every demographic population group in the United States, some have been more affected than oth-
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth FIGURE 2-1 Trends in child and adolescent obesity in males and females aged 6–19 years. NOTE: Obesity is defined as a body mass index (BMI) at or above the age- and gender-specific 95th-percentile cutoff points from the 2004 Centers for Disease Control and Prevention BMI Charts. The data on which this figure is based may have a standard error of 20 to 30 percent. SOURCE: Derived from IOM, 2005b; Ogden et al., 2002/2006. ers. For example, using data from the 2003–2004 NHANES, Ogden et al. (2006) reported obesity rates of 19 and 16 percent for white boys and girls respectively, aged 6–19 years. The rates of obesity in African American children were 18 percent for boys and 26 percent for girls, and among Mexican-American children, the rates were 22 percent for boys and 17 percent for girls. Other research has shown similar or higher rates of obesity (Sorof et al., 2004). In samples of minority children from three states, 29 percent were obese and another 19.8 percent were at risk for obesity (Jago et al., 2006). In New York City nearly half of 2,700 students surveyed were at risk for obesity (Thorpe et al., 2004). The average rate of obesity in this student population was 31 percent among Hispanic (36 percent among boys), 23 percent among African American, 16 percent among white, and 14 percent among Asian children (Thorpe et al., 2004). Childhood obesity status tracks into adulthood obesity status (Deshmukh-Taskar et al., 2006; Raitakari et al., 2005).
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth Associations Between Obesity and Chronic Disease The increased prevalence of obesity in childhood is of concern because of the strong association between obesity and cardiovascular disease risk, hypertension, dyslipidemia, and T2D that begins in childhood and continues into adulthood. Cardiovascular Disease Cardiovascular disease (CVD) is the leading cause of death and disability in the U.S., responsible for some 500,000 deaths a year. Most CVD is the result of the process of atherosclerosis whereby plaque builds up in blood vessels. About 50 percent of CVD is related to coronary artery disease. Although the clinical effects of the process do not usually show up until middle age, atherosclerosis begins in childhood and the extent of atherosclerotic change in childhood and young adulthood is correlated with elevated risk in adults (Rodriguez et al., 2006; Williams et al., 2002). Risk factors for CVD, such as elevated serum cholesterol and blood pressure occur with increased frequency in obese children and adolescents compared to children with a normal weight. In a population-based sample, approximately 60 percent of obese children aged 5 to 10 years had at least one physiological CVD risk factor, such as elevated total cholesterol, triglycerides, insulin, or blood pressure, and 25 percent had two or more CVD risk factors (Freedman et al., 1999). These risk factors are related in some degree to lifestyle factors such as diet and physical activity. The American Heart Association concludes that existing evidence indicates that primary prevention of atherosclerotic disease should begin in childhood (Williams et al., 2002). Hypertension Hypertension contributes substantially to CVD, renal failure, and premature death. The diagnosis of hypertension in children and adolescents is based on the distribution of blood pressure measurement in healthy children. Those with an average systolic or diastolic blood pressure above the 95th percentile for age, gender, and height on three separate occasions are considered to be hypertensive, while those between the 90th and 95th percentile are considered high normal or prehypertensive and are at increased risk for hypertension (AAP, 2004a). NHANES 1999–2000 found that 8 percent of children and adolescents aged 12 to 19 years had hypertension. Recent studies with participants who were predominantly minority and, on average, higher in weight, have shown around 20 to 25 percent of children with hypertension or prehypertension. The rates increase with higher BMIs,
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth from 14 percent of those with normal BMI percentile, to 27 percent of those at risk for obesity, to 39 percent of those who are obese (Jago et al., 2006). This finding differs by ethnic group, ranging from 25 percent among Hispanic to 16 percent among Asian children (Sorof et al., 2004). The relative risk for hypertension continues to be significant for obesity even when ethnicity, gender, and other factors are controlled. Comparing rates between the 1988–1994 and 1999–2000 NHANES shows that hypertension among children and adolescents has increased over time. This increase is partially accounted for by the increase in obesity (Muntner et al., 2004). Diabetes Type 2 diabetes is a complex glucose and insulin metabolic disease that can lead to serious consequences such as diabetic retinopathy, peripheral neuropathy, and kidney failure. Diabetes also increases the risk of atherosclerosis with its attendant risks of stroke, heart attack, and hypertension. Obesity in children is a major element in insulin resistance and is thus a risk factor for T2D. Type 2 diabetes has been considered an adult disease, commonly diagnosed in persons 40–74 years of age. However, the diagnosis of T2D has increased dramatically in children and adolescents and is related to body fatness. Although the rate in years past was about 5 to 10 percent of the population diagnosed with the disease, it is now estimated that, for individuals born in the U.S. after 2000, the lifetime risk of being diagnosed with T2D is 30 percent for boys and 40 percent for girls if obesity rates level off (Narayan et al., 2003). The lifetime risk of developing diabetes is even higher in some ethnic minorities at birth and at all ages. Indeed, in some communities, diabetes will become normative, that is, more individuals will have it than not. These high rates of diagnosis in children and adolescents will have considerable public health consequences: the longer a person has the disease, the greater the risk of complications. This will have an impact on schools, colleges, and workplaces, as each setting will have to deal with the increasing effects of this severe and debilitating disease in the form of days lost from school or work, discomfort, ill health, disabilities, and increased medical visits. In addition, the cost of treating diabetes, which has been estimated at $132 billion a year, will increase as today’s children and adolescents reach adulthood (American Diabetes Association, 2003). Metabolic Syndrome Metabolic syndrome is a constellation of clinical findings, including abdominal obesity, high blood pressure, dyslipidemia, and high glucose levels, that confers increased risk for CVD and T2D. Metabolic syndrome is also called “syndrome X” and insulin resistance syndrome. An analysis of data
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth from NHANES III (1988–1994) found that the overall prevalence of metabolic syndrome among all adolescents aged 12 to 19 years was 4.2 percent (6 percent in males and 2 percent in females). The syndrome was present in more than a fourth (28.7 percent) of obese adolescents, compared to 6.8 percent in adolescents at risk for obesity and 0.1 percent of those with a BMI below the 85th percentile (p <.001). Based on population-weighted estimates, this means that in the U.S. approximately 900,000 adolescents have metabolic syndrome (Cook et al., 2003). Another study found that the prevalence of metabolic syndrome increased with the severity of obesity and reached 50 percent in severely obese children and adolescents (Weiss et al., 2004). Other studies have shown clustering of components of metabolic syndrome with coronary and aortic atherosclerosis in young adults (Berenson et al., 1998). Increasing childhood obesity rates affect not only individuals and their families, but also impose direct and indirect economic costs in the forms of lost productivity, disability, morbidity, and premature death. States and communities will have to allocate new resources to prevent and treat the various metabolic syndrome comorbidities. Indeed, the great advances in the nation’s health as a result of the decline in nutritional deficiencies and the promise of advances in biomedical discoveries may be offset by the burden of illness, disability, and death resulting from metabolic syndrome and comorbidities. Therefore, schools have the opportunity and responsibility to address this nutritional and social problem within the school-age population. Bone Health and Osteoporosis Osteoporosis is a complex disorder with many contributing factors. Osteoporosis is characterized by low bone mass and microarchitectural deterioration of bone tissue, resulting in fragility and an increased risk of fracture (WHO, 2003). Osteoporotic fractures are a major cause of morbidity and disability in older people. An estimated 10 million Americans over age 50 have osteoporosis and another 34 million are at risk (DHHS, 2004a). Each year an estimated 1.5 million Americans suffer an osteoporotic-related fracture. One out of every two women over 50 years of age will have an osteoporosis-related fracture in her lifetime, with risk of fracture increasing with age (DHHS, 2004a). Health-care costs associated with osteoporotic fractures are estimated at $12–18 billion per year in 2002 dollars (DHHS, 2004a). Because of the expected increase in the number of individuals in the age range of highest risk, the incidence of hip fractures in the United States may triple by the year 2040. Although bone disease often strikes later in life, the importance of maintaining bone health and early prevention is now well recognized. It is believed that with good nutrition (especially adequate intake of calcium and vitamin D) and physical activity throughout life,
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth individuals can achieve and maintain good bone health and significantly reduce the risk of bone disease and fractures (DHHS, 2004a). Because of the importance of bone health in childhood, osteoporosis can be viewed as a pediatric disorder that manifests itself later in life. Late childhood and the adolescent years provide the window of opportunity to influence lifelong bone health. Approximately 45 percent of the adult skeleton is acquired between the ages of 9 and 17 years (Weaver and Heaney, 2006). Approximately 60 to 80 percent of bone mass is genetically determined, but hormones and lifestyle factors play a role in determining peak bone mass, which is typically achieved by the time an individual reaches the mid-teens to early 20s (DHHS, 2004a). Development of a higher peak bone mass during the adolescent years likely protects against age-related bone loss (DHHS, 2004a; Heaney et al., 2000; Weaver et al., 1999). Because the amount of bone accumulated during pubertal growth depends to some extent on the amount of calcium and vitamin D in the diet, low calcium intakes during skeletal formation may result in decreased bone mass (Heaney et al., 2000). Variations in calcium nutrition in late childhood and adolescence may account for a 5- to 10-percent difference in peak bone mass resulting in a difference of 25- to 50-percent of hip fracture incidence later in life (Heaney et al., 2000). Epidemiological evidence supports the hypothesis that low bone mass may be a contributing factor to fractures in children (Greer and Krebs, 2006). Many studies have examined the association between calcium intake during childhood and adolescence and bone health. Of 52 calcium intervention studies, all but two showed a correlation between improved bone density at higher intakes, greater bone gain during growth, reduced bone loss in the elderly, or reduced fracture risk (Heaney, 2000). Maintaining adequate calcium intake during childhood and adolescence is critical to achieving peak bone mass (Greer and Krebs, 2006). As is discussed below, the majority of older children and adolescents do not reach the recommended intakes of calcium. Iron Deficiency Iron deficiency is the most common nutritional deficiency in the world. Iron deficiency represents a spectrum ranging from iron depletion, which causes no physiological impairments, to iron-deficiency anemia, which affects the functioning of several organ systems (CDC, 1998). Iron deficiency and anemia are known to impair psychomotor development, affect physical activity and work capacity, lower resistance to infection, and, in pregnant women, increase the risk of preterm delivery and delivering a low birth-weight infant (IOM, 2001). Iron deficiency has also been linked to poorer cognition and behavioral and learning problems among school-age children and adolescents (Grantham-McGregor and Ani, 2001; Halterman
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth et al., 2001; Pollitt and Mathews, 1998). For example, one recent study investigated the relationship between iron deficiency and test scores among a nationally representative sample of school-age children and adolescents and found lower standardized math scores among iron-deficient children and adolescents, including those with iron deficiency without anemia (Halterman et al., 2001). Iron deficiency is highest among toddlers, women of childbearing age, and pregnant women. Adolescents undergoing rapid growth periods are also at risk as iron requirements increase dramatically as a result of the expansion of total blood volume, the increase in lean body mass, and the onset of menses in young females (Beard, 2000). According to NHANES (1999–2000) data of all age groups, the prevalence of iron deficiency was highest (16 percent) among females aged 16–19 years. Among children and adolescents aged 12–15 years, 9 percent of females and 5 percent of males had iron deficiency (CDC, 2002). National data indicate that only one-fourth of all females of childbearing age meet the dietary recommendations for iron (15 mg/day). Primary prevention of iron deficiency means ensuring an adequate intake of iron (CDC, 1998). This includes selecting iron-rich foods and increasing consumption of foods that enhance iron absorption. Dental Caries Although dental caries (tooth decay) is largely preventable, it is the single most common chronic disease among American children and is twice as common among low-income compared to higher-income families (DHHS, 2004b). Low-income children have about 12 times more restricted activity days due to dental-related diseases than children from higher-income families. Pain due to untreated tooth decay can lead to problems in eating, speaking, and attending to learning (CDC/DHHS, 2006). The most recent NHANES data (1999–2002) found that, among all children aged 2 to 11 years, 41 percent had dental caries in primary teeth. There are disparities evident with children in lower-income households and African American, Hispanic, and American Indian children having a higher prevalence of dental problems (DHHS, 2000, 2004b). Among children and adolescents aged 6 to 19 years, 42 percent had dental caries in permanent teeth (Beltran-Aguilar et al., 2005). Topical fluoride in toothpaste, fluoridated water, and preventive dental care were found to have a significant impact on reduction of caries risk (Touger-Decker and van Loveren, 2003). The role of diet in the etiology of dental caries is well established. There is consistently strong evidence that frequent consumption of sugar and other fermentable carbohydrates is associated with the development of caries (Lingstrom et al., 2003). Several reviews of the literature concluded a causal relationship between sugars and dental caries, although the relationship is not as strong as in the pre-fluoride era (Lingstrom et al., 2003;
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth Touger-Decker and van Loveren, 2003; WHO, 2003; Zero, 2004). Dietary habits of children remain a major component of the caries process (Dye et al., 2004). Furthermore, given the American propensity for frequent snacking, it is likely that many starch-containing processed foods also contribute to caries formation (Zero, 2004). Other important factors in caries development are food form (e.g., liquid, solid, sticky), duration of exposure, nutrient composition, sequence of eating, potential to stimulate saliva, and presence of buffers (e.g., cheese, gum containing xylitol) (Moynihan and Petersen, 2004; Touger-Decker and Mobley, 2003). Risk factors related to food consumption include nocturnal meal consumption and frequent sugar consumption (Bankel et al., 2006), and the form of sugar-containing food (Marshall et al., 2007). Intake frequency of sugars is considered the most important dietary factor in caries development (Lingstrom et al., 2003; Moynihan and Petersen, 2004). Tooth erosion refers to the gradual loss of the outside, hard surface of the tooth due to chemical, not bacterial, processes (Touger-Decker and Mobley, 2003). Tooth erosion involving frequent intake of acidic foods and beverages weakens tooth integrity and further increases caries risk (Touger-Decker and Mobley, 2003). Tooth erosion is increasing in industrialized countries and is thought to be related to increased consumption of acidic beverages (e.g., soft drinks, sports drinks, and fruit juices) (Moynihan and Petersen, 2004). Because of the synergistic relationship between nutrition and oral health, and because nutrition is a critical component of oral health, the dietary habits of children and adolescents are needed to improve oral health. Disordered Eating Behavior Relative to many other public health problems, full-syndrome eating disorders are fairly rare among children and adolescents; however, they are a serious cause of morbidity and mortality in this group. More than 10 percent of individuals with anorexia nervosa admitted to university hospitals eventually die from the disorder (APA, 2000). Anorexia nervosa (characterized by self-starvation, weight loss, intense fear of weight gain, and body image distortion) (APA, 2000) affects less than 1 percent of adolescent females (Emans, 2000). Bulimia nervosa affects 1 to 5 percent of adolescent girls (Emans, 2000) and is characterized by binge eating and purging (APA, 2000). The onset of eating disorders often occurs during adolescence or early adulthood (Emans, 2000). About 5 to 10 percent of all adolescents with an eating disorder are male (APA, 2000). Eating disorders are viewed as multifactor disorders with environmental and social factors, psychological predisposition, and biological and genetic predisposition. “Dieting” is a common entry point in both anorexia nervosa and bulimia nervosa, with the greatest risk being the group of se-
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth vere dieters (Rome et al., 2003). Sociocultural and environmental factors as they relate to ideal body shape are thought to play an important role in the development of eating disorders. Eating disorders are more common in countries and cultures where female thinness is associated with attractiveness (Rome et al., 2003). More common in the preadolescent and adolescent population are dieting and disordered eating behaviors. Dieting is a common and widespread practice especially among girls. Nationwide in 2005, 62 percent of high school girls (whites, 64 percent; African Americans, 53 percent; Hispanics, 64 percent) reported trying to lose weight during the 30 days preceding the survey. Thirty percent of high school boys were trying to lose weight (Eaton et al., 2006). Nearly 17 percent of females had gone without eating for 24 hours or more, 8 percent had taken diet pills, and 6 percent had induced vomiting or taken laxatives to lose weight during the previous 30 days (Eaton et al., 2006). Studies have shown that adolescent girls using unhealthy weight control behaviors consume fewer fruits, vegetables, and grains, and have lower intakes of calcium, iron, and other micronutrients compared to girls using healthy weight control methods or not dieting (Neumark-Sztainer et al., 2004; Story et al., 1998). A recent longitudinal study of adolescents found that dieting and unhealthy weight control behaviors among adolescents predicted weight gain, obesity status, disordered eating, and risk of eating disorder five years later (Neumark-Sztainer et al., 2006). These studies suggest that a shift is needed away from dieting and drastic weight control measures and toward lifelong healthful eating and weight control behaviors and physical activity behaviors. DIETARY INTAKE AND CONSUMPTION PATTERNS OF CHILDREN AND ADOLESCENTS Are Children’s Diets Meeting the Dietary Guidelines for Americans? The general dietary recommendations for those aged two years and older in the Dietary Guidelines for Americans (DGA) (DHHS/USDA, 2005) emphasize a diet that relies primarily on fruits and vegetables, whole grains, low-fat and nonfat dairy products, beans, fish, and lean meat. The guidelines stress meeting recommended dietary intakes within energy needs; consuming a variety of nutrient-dense foods and beverages; and limiting intakes of total, saturated, and trans fat, cholesterol, salt, and added sugars. The guidelines, as they pertain to children and adolescents, are consistent with other dietary recommendations for children and adolescents put forth by the American Heart Association (Gidding et al., 2005) and the American Academy of Pediatrics (AAP, 2004b). Despite the importance of healthful eating patterns during childhood and adolescence, studies have consistently shown that this group has poor
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth The trans fats found in hydrogenated oils not only increase low-density lipoprotein (LDL) cholesterol as do saturated fats, but also decrease high-density lipoprotein (HDL) cholesterol. These combined effects result in a larger increase in total cholesterol:HDL cholesterol ratio than is observed for dietary saturated fats (Grundy, 1999). Population trends show that the U.S. population has decreased total fat intake while increasing its caloric intake (Troiano et al., 2000), and has experienced population-wide weight gain (Ogden et al., 2006). These trends suggest that fat intake is not the only cause of obesity. A low-fat diet will not necessarily lead to weight loss if the total caloric value of the diet exceeds the individual’s energy needs. Nevertheless, fats are calorie dense, and a high fat intake is a major contributor to the high caloric intake of overweight and obese individuals (Prentice, 2001). In addition, diets high in fat tend to contain levels of saturated fats that exceed the DRI (IOM, 2002/2005). Extremely low-fat diets may be low in essential fatty acids and impair absorption of fat-soluble vitamins, but this is rare in healthy children. The primary sources of saturated fats are meats and dairy products. Trans fatty acids are found in many processed snack foods and baked products, although there are trace amounts in animal foods such as milk and meats. Consumption of Foods of Low Nutrient Density Nutrient-dense foods are those foods that provide relatively high amounts of vitamins and minerals (micronutrients) and relatively few calories (DHHS/USDA, 2005). Foods of low nutrient density are those that supply calories but no or small amounts of micronutrients. Foods of low nutrient density represent a high contribution to energy and fat intakes. The top ten foods contributing to energy intakes in children aged 2–18 years are milk, bread, cakes/cookies/quick breads/doughnuts, beef, ready-to-eat cereal, soft drinks, cheese, potato chips/corn chips/popcorn, sugars/syrup/ jams, and poultry; several of these foods such as soft drinks, chips, cakes, cookies, and pastries, are low-nutrient-dense foods (Subar et al., 1998). The CSFII 1994–1996 survey found that added sugars and fat contributed 45 percent of total energy intake in school-age children, with sugars contributing 20 percent of total calories and discretionary fat calories 25 percent (Gleason and Suitor, 2001a). In NHANES III, foods of low nutrient density contributed more than 30 percent of total energy intake among school-age children, with sweetened beverages, candy, and desserts providing about 25 percent of total energy intake (Kant, 2003). One-third of school-age children and adolescents reported eating six or more foods of low nutrient density on the day of recall. Mean intakes of vitamins and
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth minerals declined with increasing number of calorie-dense foods consumed (Kant, 2003). Consumption of foods of low nutrient density was related to higher energy consumption but was not associated with BMI. In general, greater consumption of calorie-dense foods and beverages makes it more difficult to consume sufficient nutrients without gaining weight, especially for those individuals who are inactive (DHHS/USDA, 2005). If nutrient-dense foods are selected exclusively from the various food groups in the amounts recommended, then only a relatively small amount of calories is available to be consumed as added fats or added sugars (DHHS/ USDA, 2005). This is called the discretionary calorie allowance. Calorie needs are variable in children and adolescents and depend on age, rate of growth, level of physical activity, body size and composition, and stage of sexual maturation. The amount of discretionary calories increases as total caloric need increases, and is strongly associated with physical activity level. With increasing physical activity levels, discretionary calories increase. At 1,600, 2,000 and 3,000 total calories per day, the discretionary calorie allowance would be 132, 267, and 512 calories, respectively. For sedentary children and adolescents, the discretionary calorie allowance may only be 150 to 250 calories per day. This small amount of discretionary calories does not allow consumption of many calorie-dense snacks and beverages. For example, a 20-ounce soft drink contains 250 calories. Figure 2-3 illustrates the concept of essential calories (the total energy necessary to meet recommended nutrient intakes) and discretionary calories. As can be seen for inactive children, only small amounts of discretionary calories can be consumed before caloric intake becomes excessive and weight gain results (Gidding et al., 2006). Butte (2006) estimated energy requirements for children based upon reports by the Institute of Medicine (2002/2005) and Food and Agriculture Organization of the United Nations/World Health Organization/United Nations University (2004). These estimates of energy intake recommendations for children 11 years of age and under were lower than the 1985 FAO/WHO recommendations due to decreased total energy expenditure in this age group. The committee estimated the amount of dietary energy available for discretionary energy consumption as snacks based on daily energy requirements for boys and girls as a function of age and physical activity level (IOM, 2002/2005) Estimating that approximately 25 percent of daily energy intake would be consumed at breakfast, 33 percent at lunch, and 33 percent at dinner would leave approximately 9 percent of total daily energy intake for discretionary calorie consumption. These calculations are also consistent with guidelines of the School Breakfast and National School Lunch Programs. Appendix Tables B-1 and B-2 depict the estimated energy requirements provided in the DRI report (IOM, 2002/2005) for children
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth FIGURE 2-3 Essential and discretionary calories by gender, age, and level of activity. SOURCE: Reprinted, with permission, from Pediatrics 117(2):544–559. Copyright 2006 by the American Academy of Pediatrics.
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth and include an additional four columns that show the number of calories in 9 percent of total daily energy intake allotted as discretionary calories derived from snacks. Fast Food Consumption National CSFII (1994–1996, 1998) data using 24-hour diet recalls indicate that on a typical day 33 percent of children aged 9–19 years reported eating foods obtained at fast-food and pizza outlets (excluding the school cafeteria). This included 26 percent of children aged 9–13 years and 39 percent of adolescents aged 14–19 years (Bowman et al., 2004). Fast-food consumption was prevalent in both sexes, all racial/ethnic groups, and all regions of the country. Increased consumption was independently associated with male gender, adolescent age, higher household incomes, non-Hispanic black race/ethnicity, and residence in the South. Fast-food consumption can have a negative impact on the nutritional quality of the diets of children and adolescents and may increase risk for obesity. CSFII data showed that children who consumed fast food compared with those who did not consumed more total energy (187 calories), total fat, and soft drinks, and less milk, fruits, and non-starchy vegetables (Bowman et al., 2004) compared with those who did not. French et al. (2001) found in a survey with 4,746 adolescents of multiple ethnicities that frequency of fast-food restaurant use was positively associated with total energy, energy from fat, and servings of soft drinks and french fries, and was negatively associated with servings of fruit, vegetables, and milk. A study of 101 girls between the ages of 8–12 at baseline and 11–19 years at follow-up found that the frequency of eating fast food at baseline was positively associated with change in BMI z-score. Girls who ate fast food twice a week or more at baseline had the greater mean increase in BMI z-score compared to those who ate fast food once a week or less (Thompson et al., 2004). These results suggest that fast food consumption can promote a positive energy balance and weight gain. Meal and Snack Patterns Another way of examining children’s dietary intake is to look at meal and snack patterns. Children and adolescents are more likely to skip breakfast than lunch or dinner. Based on CSFII data from 1994–1996, nearly one in five (19 percent) school-age children ate nothing for breakfast on the day of the survey (i.e., any given day), and one in three (33 percent) consumed foods and beverages that contributed less than 10 percent of their daily recommended energy allowance (Gleason and Suitor, 2001a). The percentage of children and adolescents who skipped breakfast on the day of the
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth survey increased with age: 8 percent of those aged 6–8 years, 14 percent aged 9–13 years, and 31 percent aged 14–18 years. Omitting breakfast was most frequent among adolescent females (14–18 years), with 34 percent not eating breakfast. Among all school-age children and adolescents, breakfast provided an average of 18 percent of total daily energy intake. Breakfast, when consumed, tended to be lower in fat compared to other meals (Gleason and Suitor, 2001a). Breakfast consumption has been shown to be associated with more favorable nutrient intakes and improved dietary quality in children and adolescents (Nicklas et al., 1993; Rampersaud et al., 2005). These studies found that children who eat breakfast are more likely to meet recommended intakes for vitamins and minerals than those who skip breakfast. Barton et al. (2005) found an association with cereal eating and decreased risk for obesity. In this study, however, breakfast eating was not significantly associated with decreased risk for obesity. The majority of studies, though not all, have shown that breakfast eaters are less likely to be obese (Affenito et al., 2005; Barton et al., 2005; Rampersaud et al., 2005). A recent study examined trends in adolescent obesity from 1971 to 2004 using NHANES data (Miech et al., 2006). Skipping breakfast on the day of the 24-hour dietary survey was significantly associated with being obese. Evidence also suggests that eating breakfast may improve cognitive function related to memory and increase school attendance (Rampersaud et al., 2005). Not eating lunch is less common than skipping breakfast. Just less than 10 percent of children and adolescents aged 6 to 18 years ate nothing for lunch on the day of the CSFII survey. Lunch provided nearly one-third of the energy for the day (Gleason and Suitor, 2001a). Dinner is frequently consumed by children and adolescents, but not necessarily with their family. In response to the survey question “How many times did all, or most, of your family living in your house eat a meal together?” about 22–32 percent of older children and adolescents reported eating dinner as a family only a few days a week or never (Gillman et al., 2000; Neumark-Sztainer et al., 2003). These studies along with Videon and Manning (2003) suggest that eating meals as a family may influence dietary intake of children. Increasing frequency of family dinner is also associated with consumption of more fruits and vegetables, less fried food and soft drinks, less saturated and trans fat, and more fiber, calcium, vitamins and minerals (Gillman et al., 2000; Neumark-Sztainer et al., 2003). Most U.S. children consume at least one snack per day (Cross et al., 1994), and snacking prevalence among children has increased since 1977 (Jahns et al., 2001). Data from national surveys show that, on average, school-age children snack about twice daily (Cross et al., 1994; Huang et al., 2004; Jahns et al., 2001), consuming nearly one-quarter of energy intake as snacks (Huang et al., 2004; Jahns et al., 2001).
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth The energy density of foods is higher for snacks compared to meals (Jahns et al., 2001). Based on the 1994–1996 and 1998 CSFII, children 3–5 years of age ate snacks averaging 146 ± 3 calories, children 6–11 years of age ate snacks averaging 197 ± 5 calories, and adolescents aged 12–19 years ate snacks averaging 274 ± 11 calories (Huang et al., 2004). Food Choice Behavior Studies of the effects of children’s consumption patterns on parents restricting energy-dense foods suggests that severe restriction of preferred foods of low nutrient value may increase their desire for such foods (Benton, 2004; Fisher and Birch, 1999). Taste perception is likely another important factor in food choices (Drewnowski, 1997). Factors that determine taste preference include genetic background (Birch, 1999; Mennella et al., 2005) and early life exposure (Birch, 1998; Birch and Fisher, 1998; Mennella et al., 2006). Because schools represent only a small part of the daily eating opportunity for children it is not clear whether restriction of energy-dense foods of minimal nutritional value in the school environment will encourage school-age children to consume them. Studies of students’ perceptions of factors influencing food choices suggest that they are open to information about healthful choices and willing to make changes to improve their diets. O’Dea (2003) studied the responses of students aged 7–17 years to suggested strategies to overcome barriers to healthful eating. This study found that children and adolescents were willing to make healthful behavior changes and looked to parents and teachers for support. Neumark-Sztainer et al. (1999) assessed perceptions of factors that affect food choice behaviors among adolescent boys and girls from inner-city schools. From focus group discussions, the study identified a broad range of factors such as hunger, taste appeal, availability, and convenience that influence food choice behavior. The study concluded that knowledge of these factors could be useful in developing ways to make healthful food more appealing to adolescents and encourage healthful behaviors. SOCIODEMOGRAPHIC FACTORS AFFECTING DIETS IN CHILDHOOD AND ADOLESCENCE Gender Gender differences in dietary intakes emerge as children move into adolescence. During childhood, food intakes of girls and boys tend to be similar. Because of increased rates of growth and body size, adolescent males eat larger quantities of food on average than female adolescents, so they are more likely to meet recommended daily intakes for vitamins
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth and minerals. Dietary surveys show adolescent males eat more servings of grains, vegetables (including french fries), dairy, and meat compared to adolescent females (Enns et al., 2003; Gleason and Suitor, 2001a). Adolescent males are also more likely to have diets higher in total fat and saturated fat (Gleason and Suitor, 2001a) and to consume larger amounts of soft drinks (French et al., 2003). As a group, adolescent females are more likely to have lower intakes of vitamins and minerals (Enns et al., 2003; Gleason and Suitor, 2001a; Story et al., 2002b). They are also more likely to skip meals, especially breakfast, than are adolescent males (Gleason and Suitor, 2001a). In fact, dietary data show that adolescent females aged 14–18 years have the poorest diets compared to all other age or gender groups (Gleason and Suitor, 2001a). Economic Status Children in low-income families fare less well than children in more affluent families on many health status indicators (DHHS, 2000; FIFCFS, 2005). In 2003, 18 percent of all children up to 17 years of age lived in poverty. The poverty rate was higher for African American (34 percent) and Hispanic (30 percent) children compared to white children (10 percent) (FIFCFS, 2005). About 12.4 million children (16.9 percent) lived in households that were classified as food insecure at times in 2005. Households are classified as food insecure based on reports of difficulty obtaining enough food, reduced dietary quality, and anxiety about food supplies (USDA/ERS, 2006). Several studies have shown that children in families below the poverty level are less likely than higher-income children to have a healthy diet (Devaney et al., 1995; FIFCFS, 2005; Fox and Cole, 2004; Munoz et al., 1997). Studies of trends in obesity show that patterns between socioeconomic status and overweight are complex, but such associations can be drawn (Melgar-Quinonez and Kaiser, 2004; Ritchie et al., 2003; Sturm, 2005; Wang and Zhang, 2006). In these studies, children and adolescents in low-income families had higher intakes of total and saturated fat and consumed less fruit and dairy products. Low socioeconomic status has been shown to be a strong predictor of low fruit and vegetable intake among adolescents (Neumark-Sztainer et al., 1996). This may be related to financial resources to purchase fruits and vegetables and less access to affordable, quality fruits and vegetables in low-income communities. Current child poverty rates highlight the importance of the federal child nutrition programs such as the National School Lunch Program (NSLP) and the School Breakfast Program (SBP), which provide a food and nutrition safety net for low-income children to help reduce hunger and improve health. In the 2005–2006 school year, the NSLP provided lunch to 29 mil-
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth lion children and adolescents on an average day. Of these, 17 million (59 percent) received a free or reduced-price school lunch (FRAC, 2006). Race and Ethnicity National CSFII data for school-age children found that African American and Hispanic children and adolescents were less likely to meet recommendations for limiting total and saturated fat than their white counterparts, and total consumption of milk products and calcium was lowest among African American children and adolescents. White children had the highest intake of added sugars and soft drinks, although African Americans drank more fruit drinks (Gleason and Suitor, 2001a). Other studies have also shown that white children drank more milk than African American children, and that African American girls drank more fruit drinks (Storey et al., 2004; Striegel-Moore et al., 2006). DIETARY TRENDS OVER TIME AMONG SCHOOL-AGE CHILDREN Changes over time in school-age children’s food consumption (Gidding et al., 2005) include increased consumption of foods prepared away from home; increased percentage of total calories from snacks; increased consumption of calorie-dense foods; increased portion sizes of foods; increased consumption of sweetened beverage; and decreased consumption of milk. Trends in Dietary and Nutrient Intakes A recent study examined dietary intake trends among children and adolescents over a 20-year period using data from three USDA national surveys: Nationwide Food Consumption survey 1977–1978; CSFII 1989–1991; and CSFII 1994–1996, 1998 (Enns et al., 2002, 2003). Among children 6 to 11 years old and adolescents 12 to 19 years old, increases in dietary intakes over time were found for soft drinks, total grain products, snack chips, fried potatoes, fruit drinks, and candy (Enns et al., 2002, 2003). The intake of chips, crackers, popcorn, and pretzels roughly tripled from the mid-1970s to the mid-1990s for both children and adolescents. The intake of soft drinks roughly doubled during this same period for children and adolescent females and tripled among adolescent males. In both age groups, decreases were found for total milk intake. Total fat intake and percentage of calories from fat decreased, but this was due in part to increased carbohydrate in-
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth take (Enns et al., 2002, 2003). For example, among children, fat intake decreased by 100 calories or less, but carbohydrate intake increased by about 150–200 calories (Sturm, 2005). NHANES trend data from the 1970s to 1999–2000 also found a decrease in dietary fat and percentage of energy from fat and concomitant increases in carbohydrate intake among children and adolescents (Briefel and Johnson, 2004). The CSFII data showed increases in iron and thiamin intake, and decrease in vitamin B12 in children and adolescents (Enns et al., 2002, 2003). Dietary Changes Among Children National data indicate that diet adequacy deteriorates as individuals get older; children, especially infants and young children, have diets that are more nutritionally adequate than those of adolescents (Devaney et al., 2005). Lytle et al. (2000), in a longitudinal study of 291 student participants, found that diet quality declines as children move from middle childhood into adolescence; intake of fruits, vegetables, and milk decreases and consumption of soft drinks increases. The study showed that fruit consumption fell by 41 percent between the third and eighth grades and vegetable consumption fell by 25 percent. Additional evidence from a longitudinal study of girls (Mannino et al., 2004) showed that dietary quality declined between 5 and 9 years of age, with a larger proportion of girls at 9 years of age having inadequate intakes of dairy, fruits and vegetables, and several nutrients than they did at an earlier age. Lin et al. (2001) determined that an increase in eating out was a factor in the age-related adolescent decline in diet quality. Trends in Meal Patterns and Snacking Breakfast consumption by U.S. children and adolescents has declined over time. For example, between 1965 and 1991, breakfast consumption declined 9 percent in children aged 8 to 10 years and 13 to 20 percent in adolescent males and females. The greatest decline (20 percent) was in adolescent girls (Siega-Riz et al., 1998). The nutritional quality of foods consumed at breakfast has improved since 1965, especially in substitution of lower fat for full-fat milk (Siega-Riz et al., 1998). The introduction of the SBP has increased breakfast consumption among children in low-income areas. The Bogalusa Heart Study found that from 1973 to 1978, there was a marked increase from 8 to 30 percent in the percentage of children who skipped breakfast. When school breakfast service was introduced in the district in 1981, the percentage of children skipping breakfast declined to 12 percent (Nicklas et al., 2004). Nationally representative data also show that the prevalence of snack-
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth ing has increased in school-age children and adolescents from 1977 to 1996. The average size of snacks and energy content per snack remained relatively constant during this period; however, the number of snacks eaten per day rose significantly, thus increasing the average daily energy from snacks (Jahns et al., 2001). Nielsen and colleagues (2002) found that CSFII data showed the increase in energy intake occurred predominantly from snacks particularly from 1989 to 1996 among adolescents. Thus the increase in snacking may be contributing to the epidemic of obesity in children and adults (Jahns et al., 2001; Zizza et al., 2001). Trends in Portion Sizes Portion sizes have increased steadily over the past 30 years (Nielsen et al., 2002; Young and Nestle, 2002). Data suggest that the trend toward larger portion sizes began in the 1970s, increased sharply in the 1980s, and has continued to increase (Young and Nestle, 2002). Between 1977 and the mid-1990s, food portion sizes for Americans aged 2 years and older increased both inside and outside the home for salty snacks, desserts, soft drinks, fruit drinks, french fries, hamburgers, cheeseburgers, and Mexican-type foods (Nielsen et al., 2002). Larger portions not only contain more calories, but also encourage people to eat more. A recent controlled laboratory study found that increasing the portion size of all foods resulted in a significant increase in energy intake that was sustained over two days (Rolls et al., 2006). Because portion size affects energy balance, there is a need for greater attention to food portion size and consuming recommended serving sizes, such as those in the DGA. LIMITATIONS IN RESEARCH ON CHILDREN’S DIETS Measuring what people eat and drink is one of the most challenging aspects of population-based nutrition research studies. Studies assessing dietary intake patterns; nutrient intakes and nutrition; and health and disease relationships, especially population-based epidemiological studies, rely predominantly on self-reporting using dietary assessment instruments such as 24-hour recalls, diet records, or food frequency questionnaires. Although it is recognized that self-reported dietary intake data reflects underestimates of food intake and, in turn, energy intake, the magnitude of this effect in different populations is not clear. Studies using doubly-labeled water show that underreporting of food intake is pervasive in adults. Underreporting constitutes anywhere from 10 to 45 percent of the total, depending on the age, gender, and weight of the respondents (Johnson, 2000). Underreporting tends to increase in prevalence as children mature, is more common
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Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth among women than men, and is higher among overweight and obese adults (Johnson, 2000). Other factors associated with underreporting include perceived social desirability of intake patterns, body image dissatisfaction, dieting, and greater eating restraint (Maurer et al., 2006). Social desirability may influence not only self-reported total energy intake, but also the likelihood of underreporting socially undesirable food intake patterns such as the consumption of high-fat, high-sugar foods and beverages (Maurer et al., 2006). On the other hand, social desirability of healthy foods such as fruits and vegetables can result in overreporting (Maurer et al., 2006). Misreporting of food intake may result from errors in the estimation of portion sizes, inability or unwillingness to record or remember everything that was eaten, unintentional omission of certain foods or portions, and deliberate misreporting. Engaging in the recording process or anticipating the report of food intake may cause an individual to temporarily change the way he or she eats (Maurer et al., 2006). It is also more difficult to remember what was eaten between meals, which is an issue for children and adolescents who may snack frequently. Dietary intake research on young children also presents special challenges; the child’s parent or teacher may be relied on to recall the child’s intake, thus introducing a third party and further complicating the assessment process (Goran, 1998).