Chapter 4: Normal Adolescent Nutrition Pamela S. Hinton, PhD

1. Chapter 4: Normal Adolescent NutritionPamela S. Hinton, PhD

2. Reader Objectives After studying this chapter and reflecting on the contents, you should be able to: • 1. Understand nutritional regulation of the hormones that moderate growth and sexual maturation. • 2. Describe gender differences in growth and development and in nutrient requirements.

3. Reader Objectives, cont. • 3. Appreciate how psychosocial development during adolescence affects health-related behaviors, including dietary patterns. • 4. Identify and describe sociodemographic factors affecting dietary patterns. • 5. Describe trends in chronic disease incidence among adolescents.

4. Growth and Development

5. G&D: Physical Growth • Peak height velocity. The adolescent growth spurt takes 2-4 years to complete and is generally longer in boys than in girls. • The average height velocity is 5-6 cm/year during adolescence; peak height velocity is 8-10 cm/year. • Girls, on average, begin their pubertal growth spurt at age 9 years and achieve their maximal rate of linear growth, i.e., peak height velocity (PHV), at an average chronological age of 11.5 years.

6. G&D: Body composition. During adolescence, girls gain fat mass (FM) at an average rate of 1.14 kg per year. In contrast, boys do not experience a significant increase in absolute fat mass. Boys also gain fat-free mass (FFM) at a greater rate and for a longer period of time than girls; as a result, boys are relatively leaner than girls post puberty. At ages 8-10 boys, on average, have 15% body fat and 24 kg of FFM. At the end of puberty, ages 18-20 years, males have 13% body fat and 60 kg of FFM. In contrast, girls have 20% body fat and 24 kg FFM at age 8-10 years.

7. G&D: Bone growth & mineralization • Bone mass doubles between the onset of puberty and young adulthood. Bone growth is greatest approximately 6 months after PHV; approximately 25% of peak adult bone mass is acquired during the 2 years of peak adolescent skeletal growth. • Growth of the skeleton occurs via modeling which changes both the size and shape of the bones. Bones increase in length by ossification of the growth plates and in diameter by periosteal apposition and endosteal resorption. • When the growth plates fuse post-puberty, bone mass development (BMD) is 90-95% of peak BMD. Boys are, on average, 10% taller and have 25% greater peak bone mass than girls because of their later pubertal onset and longer growth spurt.

8. Hormonal Mediators of the Adolescent Growth Spurt • Pattern of hormone secretion. • Normal physical growth and development during puberty depends on the integration of the growth hormone/insulin-like growth factor and gonadotropin axes. • Nutritional and metabolic signals, in part, control these hormonal systems by acting on the hypothalamus and pituitary gland.

9. Hormonal Mediators of the Adolescent Growth Spurt, cont. • During childhood, the activity of the hypothalamic-pituitary-gonadal axis is suppressed by the central nervous system (CNS). • Hormones have effects on bone, adipose tissue and sexual development.

10. Assessment of Growth & Development • Serial measurements of height and weight are plotted on height-for-age, weight-for-age, and weight-for-height growth charts from the National Center for Health Statistics are used to evaluate growth. • Height growth potential is calculated from parental height. • Skeletal age is assessed using radiography of the left hand and wrist. An open epiphysis indicates skeletal immaturity and potential for additional growth.

11. Adolescent Growth Disorders • Pathological causes of short stature. A teenager whose weight percentile is declining may be suffering from chronic illness, poor dietary intake, possibly of psychosocial etiology. Other pathological causes include: endocrine disorders such hypothyroidism and GH deficiency; intrauterine growth retardation; chromosomal defects, Turner, Down, and Prader-Willi syndromes; and skeletal dysplasia.

12. Adolescent Growth Disorders • Pathological causes of tall stature. Endocrine causes of tall stature include hyperthyroidism, precocious puberty, and GH-secreting tumors. Adolescents with precocious puberty will end up with compromised adult height because estrogen and androgen levels peak early, causing premature fusion of the growth plates. Klinefelter, Marfan, Sotos, and Beckwith-Widermann syndromes, are rare genetic disorders that result in tall stature.

13. Cognitive and Psychosocial Development During Adolescence Cognitive and Affective Development • The brain develops during puberty; in particular, areas involved in regulation of behavior and emotion and in perception and evaluation of risk and reward undergo considerable change. Cognitive development during adolescence results in increased self-awareness, self-direction and self-regulation. • During early adolescence, teenagers improve their deductive reasoning, information processing, specialized knowledge. The capacity for abstract, multidimensional, planned and hypothetical thought increases into middle adolescence.

14. Psychosocial Development • The cognitive and affective development that occurs during adolescence changes a teenager’s self-concept and self-esteem. Adolescents are concerned with the identity that they project to others. The discrepancy between an adolescent’s self-identity and the expectations of others may be problematic. • Rapid pubertal development or pubertal onset that deviates from one’s peers also may result in maladaptive behaviors.

15. Psychosocial Development, cont. • In females, early maturation is associated with increased affective disorders, delinquency and drop-out rates, and pregnancy. • In boys, early physical maturation has mostly positive consequences, namely increased social status and high self-esteem. In contrast, males with late pubertal onset are more likely to engage in status-seeking anti-social behaviors. • Thus, biological and social factors interact to affect behaviors, including those with long-term effects on health.

16. Youth Risk Behavior Surveillance Study (YRBSS) Study found that: • In the nearly one-half of high school students use alcohol, • 30% binge drink, • 25% report current marijuana use. • The prevalence of cocaine, inhalant, heroin, and metamphetamine is lower; lifetime rates of use range from 3-15%. • 5% reported using illegal steroids during the lifetime

17. Nutrient Requirements and Temporal Consumption Trends • Absolute nutrient requirements are increased in adolescence compared to childhood due to increased growth and body size. • Adolescent males have greater requirements for most nutrients compared to females due to differences in growth and development. • The exception is iron; postmenarcheal adolescent girls need more iron than boys due to menstrual blood losses [32].

18. Macronutrients • Average daily energy consumption assessed in NHANES I (1971-1974) and III (1988-1994) has remained relatively constant, except for adolescent females whose energy intake increased from 1,735 to 1,996 kcal/d. • The proportion of energy derived from fat and saturated fat decreased over time, but remains above the recommendations in the Dietary Guidelines at 33.5% for total fat and 12.5% for saturated fat. In children over 6years , 10-18% of saturated fat and 5-10% of total fat was consumed in 2%-fat and whole milk products.

19. Minerals • Calcium. Recent longitudinal data of bone mineral deposition suggest that calcium requirements may be higher--1500 mg for girls and 1700 mg for boys during peak calcium accretion. • Iron. Iron requirements increase during adolescents to meet the demands of growth and inevitable losses. Iron is lost from the gastrointestinal tract, skin, urine, and menstrual blood in females. • Sodium. Average daily sodium consumption has increased by approximately 1000 mg for adolescent boys and girls between NHANES I (1971-1974) and NHANES 1999-2000.

20. Vitamins: Vitamin D. • Dietary intake of vitamin D among adolescents varies by ethnicity; Non-Hispanic Caucasians had the highest intakes of vitamin D and African Americans the lowest. As a group, adolescent males are more likely to have adequate vitamin D intakes than females and older males. • Because the prevalence of lactose intolerance is higher among African Americans (75%) than Hispanics (53%) and Caucasians (6-22%) avoidance of dairy products may explain the reduced vitamin D intakes among African American adolescents.

21. Vitamin D cont. • In 2003, the FDA approved vitamin D fortification of calcium-fortified juices and juice drinks. African Americans and Mexican Americans who avoid dairy products may benefit from these fortified products; for example, 8 ounces of fortified orange juice provides up to 2.5 µg (100 IU) vitamin D.

22. Dietary Patterns • Serving Size-Average serving sizes for foods eaten at home and away from home have increased during the past 30 years. Foods frequently consumed by adolescents--salty snacks, ready to eat cereals, and soft drinks have significantly increased. • Food Groups-Adolescents do not consume the recommended number of servings of fruits, vegetables and dairy products and they consume excessive amounts of added sugar, fat and saturated fat.

23. Dietary Patterns, cont. • Skipping Breakfast-1/5th of adolescents report skipping breakfast. • Fast Food Consumption-Most adolescents frequently eat meals and snacks away from home. In one study, 26% of all meals and snacks were consumed away from home, accounting for 32% of total energy

24. Sociodemographic Moderators of Dietary Intake • Gender, ethnicity, parental income and education affect diet quality in adolescents. • Advertising and marketing of foods and beverages influences the food preferences, purchase requests, purchase and consumption of children and youth. • The recent increase in adolescent overweight and obesity has brought the food environment in schools under increasing scrutiny.

25. Health Status of US Adolescents • Increased overweight and obesity • Incidence of diabetes, hypertension, and hyperlipidemia in patients with cardiovascular disease have been described as the “metabolic syndrome” • Iron deficiency in girls • Children are starting to smoke at a younger age • Adolescent pregnancy • Eating disorders

26. Chapter 4 Special Section:Public Health Nutrition Programs for Children Rachel Colchamiro, MPH, RD, LDNJan Kallio, MS, RD, LDN

27. Public Health Nutrition Programs for Children Critical Need for Pediatric Public Health Nutrition Services: • Prematurity • Overweight • Anemia • Breastfeeding • Hunger and Food Insecurity

28. Federal Public Health Nutrition Programs • Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) • Food Stamp Program • National School Lunch Program • School Breakfast Program • Summer Foodservice for Children • Special Milk Program • Child and Adult Care Food Program • Commodity Supplemental Food Program • The Emergency Food Assistance Program

29. Other Federal Programs That Respond to the Nutritional Needs of Infants, Children and Adolescents • Head Start and Early Head Start • Early Intervention Nutrition Surveillance Systems in the US • Pregnancy Nutrition Surveillance System • Youth Risk Behavior Surveillance System • National Health & Nutrition Examination Survey