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Comprehensive Notes — Childhood and Adolescence (Transcript Summary)

Body Composition in Childhood and Adolescence

  • Major sex differences emerge in the acquisition of body fat and lean weight during adolescence. Fat mass is influenced by sex hormones: estrogen and progesterone in females; testosterone in males. Lean body weight gains are also unequal between sexes, with boys typically showing greater gains. Within lean weight, age-related patterns include: boys tend to double their lean weight during adolescence, whereas girls show a more modest rise (approximately 50%).

  • Protein requirements (RDI) differ by age and sex: for 9–13 years, boys require about 0.94\ \frac{g}{kg} of body weight and girls about 0.87\ \frac{g}{kg}; for 14–18 years, boys require about 0.99\ \frac{g}{kg} and girls about 0.77\ \frac{g}{kg}.

  • Bone development differs by sex, with males generally experiencing greater bone gains than females during adolescence.

Nutritional Requirements and Bone Health

  • From birth to puberty, the skeleton increases in mass by roughly seven-fold, with a further approximately three-fold gain during adolescence. Bone accretion happens earlier and to a lesser extent in girls compared with boys. This underlines the critical importance of nutrients (especially calcium and vitamin D) during growth to maximize peak bone mass and reduce future fracture risk.

  • The literature includes Weaver (2016) as a key reference, with discussions of evidence grading (e.g., Table 1: Evidence grading system). The grading framework classifies evidence as A (strong), B (moderate), C (limited), and D (inadequate). Examples of evidence types include large randomized controlled trials (RCTs), meta-analyses, prospective cohort studies, and, when applicable, clinical experience or descriptive studies.

  • The Bone health discussion includes a reader article by Weaver (Calcium and peak bone mass) and related web resources (e.g., Purdue University news release and ARHP bone imagery), illustrating how calcium status and bone mass relate to adolescent health.

Calcium and Bone Health

  • Calcium is central to bone health across childhood and adolescence. Inadequate calcium intake is linked to lower bone mass and increased fracture risk, with bone mass accumulation continuing across life. Adequate intake during adolescence supports peak bone mass attainment.

  • Calcium requirements (RDI) are the same for boys and girls in adolescence, reflecting the need for strong bones regardless of sex, though bone gains differ by sex. The Calcium RDIs are:

    • \text{RDI}_{Ca}(9-13\text{ yrs}) = 1000-1300\ \text{mg/day}

    • \text{RDI}_{Ca}(14-18\text{ yrs}) = 1300\ \text{mg/day}

  • EAR data and mean intakes indicate that a substantial proportion of adolescents do not meet the EAR for calcium. For example, mean intakes in different age groups show varying percentages meeting the EAR, highlighting the need for dietary strategies to improve calcium intake.

  • Calcium sources in the diet include dairy products (milk, yogurt, cheese), fortified foods, and plant-based sources like tofu and certain legumes. Weight-bearing activity also supports bone health and calcium utilization.

  • A key figure illustrates bone mass trajectories: continued bone mass accumulation underscores the lifelong importance of calcium intake during adolescence.

Iron and Anemia

  • Both adolescent boys and girls have high iron requirements during growth. The RDI for iron is approximately:

    • \text{RDI}_{Fe}(9-13\text{ yrs}) = {8-11}\mathrm{mg/day} (boys), {8-15}\mathrm{mg/day} (girls)

    • \text{RDI}_{Fe}(14-18\text{ yrs}) = {8-11}\mathrm{mg/day} (boys), {8-15}\mathrm{mg/day} (girls)

  • Mean intakes of iron among adolescents show substantial intake levels, with boys typically reporting higher intakes than girls in certain age groups (e.g., 4–8 years: boys ~10.5 mg; 9–13 years: ~13.6 mg; 14–16 years: ~16.3 mg; girls in corresponding groups are generally lower).

  • The prevalence of iron deficiency and depleted iron stores varies by country and time period, with international data illustrating differing levels of ferritin and anemia. In Australia, the prevalence of iron depletion and iron deficiency varies by survey year and age group, indicating iron status remains a public health consideration for adolescents.

Zinc and Trace Minerals

  • Zinc is essential for growth and sexual maturation and its requirement and retention rise during adolescence. The RDI for zinc is:

    • \text{RDI}_{Zn}(9-13\text{ yrs}) = 6-13\ \mathrm{mg/day} (boys), 6-7\ \mathrm{mg/day} (girls)

    • \text{RDI}_{Zn}(14-18\text{ yrs}) = 6-13\ \mathrm{mg/day} (boys), 6-7\ \mathrm{mg/day} (girls)

  • Across age groups, mean zinc intakes rise with age for boys (from ~9.7 mg to ~15.3 mg) and are slightly lower for girls (from ~8.3 mg to ~10.0 mg). The CNPAS data indicate high percentages meeting EAR except for some subgroups (e.g., 14–16-year-old boys).

Energy, Diet Patterns, and Obesity

  • Energy intake data show age-related increases, with rec ranges provided in megajoules (MJ) and reference ranges for different youth cohorts. In general, energy needs rise through childhood into adolescence, with macronutrient distribution contributing the majority of energy:

    • Carbohydrates (CHO) provide around 50% of energy

    • Fat contributes about 30% of energy

    • Cereal products are major energy sources (~36-40% of total energy)

    • Milk and dairy products contribute ~14-17%

    • Meat, vegetables, and confectionery provide additional energy contributions, with confectionery around ~5% and non-alcoholic beverages around ~7%

  • The prevalence of overweight and obesity among Australian youth has risen across earlier decades: 1985 (boys 9%, girls 10%), 1995 (boys 15%, girls 16%), 2007 (boys 25%, girls 30%); by 2011–2013, about 25% of youth were overweight or obese, with no gender difference reported.

  • Obesity is associated with metabolic and psychological risks, including early onset of chronic diseases, potential dyslipidemia tracking from childhood to adulthood, and possible barriers to normal growth if extreme.

Eating Disorders and Disordered Eating

  • Eating disorders covered include anorexia nervosa, bulimia nervosa, binge eating disorder, and disordered eating patterns (e.g., restrained eating, fear of fatness). Pica is also noted as a concern.

  • Anorexia nervosa is characterized by refusal to maintain a minimally normal body weight for age/height, intense fear of gaining weight, disturbance in body weight/shape perception, and often absence of menstruation. Warning signs include dramatic weight loss, obsessive exercise, hair loss or thinning, cold sensitivity, amenorrhea in post-pubertal females, lethargy, and insomnia.

  • Bulimia nervosa involves episodes of excessive food consumption with lack of control, followed by compensatory behaviors (e.g., vomiting, laxative use, excessive exercise). Warning signs include dental discoloration, calluses on knuckles/backs of hands, weight fluctuations, and frequent bathroom use. Case examples illustrate real-life scenarios of binge eating and purging behaviors.

  • Disordered eating patterns are more prevalent in females than males and encompass a range of behaviors and body image disturbances that can impact nutrition and health.

Alcohol and Adolescent Health

  • Alcohol affects nutrient storage and metabolism and can be toxic to cells in the GI tract, liver, and pancreas at high intakes. Regular or excess alcohol consumption is linked to chronic diseases (liver disease, obesity, hypertension, cancers).

  • Historical data (1995 NNS) show higher experimentation with alcohol among older adolescents, with early-life drinking patterns evolving over time. More recent surveys (AHS 2011–2012) indicate that adolescent alcohol intake comprises a small percentage of total energy intake, with males typically contributing slightly more than females.

  • National data (2019) show that a large majority of 14–17-year-olds have never consumed a full serving of alcohol, and a shifting trend toward reduced drinking in youth populations over time. By age 16–18, many are still not regular drinkers, reflecting ongoing public health concerns and changing social norms.

  • Overall, adolescents are more susceptible to alcohol’s effects than adults, with lower tolerance and potential impairment of judgment from even small quantities. There is a positive association between drinking and smoking, and alcohol intake tends to increase with age.

Adolescent Nutritional Issues and Practical Implications

  • The adolescent period is characterized by rising obesity prevalence, micronutrient inadequacies (notably calcium, iron, zinc), and a peak risk period for disordered eating in females, which can lead to nutrient inadequacies.

  • Ethical and practical implications include ensuring access to healthy foods, promoting healthy snacking, maintaining healthy body weight, and addressing vegetarian diets with appropriate planning to meet nutrient needs.

  • Real-world relevance includes case studies and school talks on healthy eating behavior, emphasizing practical solutions and evidence-based strategies to optimize nutrition across the lifespan.

Dietary Guidelines and Food Groups for Adolescents (Five Food Groups)

  • Dietary guidelines emphasize five food groups and the appropriate number of serves for children and adolescents, with recommendations varying by age and activity level. The groups include:

    • Vegetables and legumes/beans

    • Fruits

    • Grain (cereal) foods, mostly wholegrain and/or high-fiber varieties

    • Lean meats and poultry, fish, eggs, tofu, nuts and seeds, and legumes/beans

    • Milks, yogurts, cheese, and/or alternatives (mostly reduced fat)

  • Hydration and beverages are also considered, with an emphasis on water as the primary drink and limiting caffeinated beverages.

  • The guidelines provide guidance on not only the number of serves but also the quality of foods (e.g., choosing wholegrain cereals, limiting saturated fat, and avoiding excessive added sugars).

  • The Dietary Guidelines also hint at the proportion of energy contributed by major food groups (e.g., cereals as a major energy source) and highlight the importance of nutrient-dense options to meet EAR/RDI targets.

Case Studies and Practical Applications

  • Case Study 5 (What important points would you cover in a 30-minute talk to year 10 students about healthy eating): Healthy snacking, healthy body weight, and vegetarian diets.

  • Case Study 52 (Similar prompt in a different context) reinforces the emphasis on practical topics for adolescents: healthy snacking, healthy weight, and vegetarian diets.

  • These case studies illustrate how to translate theory into practice for real-world health promotion in school settings.

Next Week’s Lecture

  • Topic 7: Encourage healthy eating. This signals a continuation of applying nutrition science to practical health promotion for adolescents, with a focus on actionable strategies to support healthy dietary patterns.

References mentioned in the transcript include Weaver (2016) on calcium and peak bone mass, the Osteoporosis International article (NOF/Weaver adaptations), and related reader links for bone health and nutrition education.