Adolescent Nutrition: Meeting Needs

Key Nutrition Concept #1

• Nutrition needs should be determined by the degree of sexual and biological maturity, not chronological age.

Key Nutrition Concept #2

• Unhealthy eating behaviors common among adolescents include frequent dieting, meal skipping, unhealthy dieting practices, and frequent consumption of foods high in fat and sugar, such as fast foods, soft drinks, and savory snacks.

Nutritional Needs in a Time of Change Affect

• Biological changes
• Psychosocial changes
• Cognitive changes
• Rapid growth increases nutrient needs
• Desire for independence may cause adoption of health-compromising eating behaviors

Health-compromising eating behaviors

• Excessive dieting
• Meal skipping
• Use of unconventional nutritional and nonnutritional supplements
• Fad diets

Health-enhancing eating behaviors

• Healthful eating practices
• Physical activity
• Interest in a healthy lifestyle

Normal Physical Growth and Development

• Puberty occurs during early adolescence
• Biological changes of puberty include sexual maturation, increases in height and weight, accumulation of skeletal mass, and changes in body composition
• The sequence of maturation events is consistent, but there's great individual variation in the age of maturation
• Variations in reaching sexual maturity affect the nutrition requirements of adolescents
• Sexual maturation (or biological age)—not chronological age—should be used to assess growth and development and nutritional needs

Sexual Maturation Rating (SMR) or "Tanner Stages"

• Sexual Maturation Rating (SMR) a.k.a. "Tanner Stages" is a scale of secondary sexual characteristics used to assess the degree of pubertal maturation
• SMR 1 = prepubertal growth & development
• SMR 2-4 = occurrences of puberty
• SMR 5 = sexual maturation has concluded

Maturation and Growth of Females

• Menarche (onset of first menstrual period) occurs 2-4 years after initial development of breast buds
• Age of menarche ranges from 9 to 17 years
• Peak linear growth occurs ~6 to 12 months prior to menarche
• Severely restrictive diets may delay or slow growth

Maturation and Growth of Males

• Males show a great deal of variation in chronological age at which sexual maturation takes place
• Peak velocity of linear growth occurs during SMR 4 & ends with the appearance of facial hair at ~age 14.4
• Linear growth continues throughout adolescence, ceasing at ~age 21

Changes in Weight, Body Composition, and Skeletal Muscles in Females

• Peak weight gain follows linear growth spurt by 3 to 6 months
• Gain of ~18.3 pounds per year
• Average lean body mass decreases
• 44% increase in lean body mass (LBM)
• 120% increase in body fat
• 17% body fat is required for menarche to occur
• 25% body fat needed to maintain normal menstrual cycles

Changes in Weight, Body Composition, and Skeletal Muscles in Males

• Peak weight gain happens at the same time as peak linear growth & peak muscle mass accumulation
• Peak weight gain is ~20 lb per year
• Body fat decreases to ~12%
• ~Half of bone mass is accrued in adolescence

Normal Psychosocial Development

• Adolescents develop a sense of personal identity, a moral & ethical value system, feelings of self-esteem or self-worth, and a vision of occupational aspirations
• There are three periods of psychosocial development including early adolescence (11 to 14), middle adolescence (15 to 17), and late adolescence (18 to 21)
• The need to fit in can affect nutritional intake due to who they eat with and where they eat
• Peer influences may be greater than family and these influences can either improve or lead to poor dietary intake

Health and Eating-related Behaviors during Adolescence

• Factors affecting eating behaviors include peer influence, parental modeling, food availability, preferences, & cost, personal & cultural beliefs, mass media, and body image

Conceptual Model for Factors Influencing Eating Behavior of Adolescents

• Macro systems consist of socioeconomic-political systems, food-production and distribution systems, food availability, and mass media
• Microenvironmental aspects consist of cultural groups, social/cultural norms and values, food trends and fads, fast foods, and school meals
• Environmental: Immediate Social Environmental aspects consist of family unit characteristics, parenting practices, parent modeling, home environment, family meal patterns, peer norms, and influences
• Cognitive-affective aspects consist of personal health values and beliefs, functional meanings of food, body image, and self-concept
• Behavioral patterns consist of food preferences self-efficacy, food-related skills, and eating practices
• Biologic: factors consist of pubertal status, growth, physiologic needs, genetic predisposition, and health status
• Busy lives lead to different eating styles, with little time to sit down for a meal
• Snacking and meal skipping is common
• Fast food restaurants/eating away from home increase
• High consumption of soft drinks and not enough nutrient dense beverages

Vegetarian Diets during Adolescence

• About 4% of adolescents report following a vegetarian diet for reasons such as cultural or religious beliefs, moral or ethical concerns, health beliefs, to restrict fat and/or calories, and as a means of independence from family

Types of Vegetarian Diets and Food Excluded

• Semi- or partial-vegetarian diets exclude red meat
• Lacto-ovo-vegetarian diets exclude meat, poultry, fish, and seafood
• Lacto-vegetarian diets exclude meat, poultry, fish, seafood, and eggs
• Vegan (total vegetarian) diets exclude meat, poultry, fish, seafood, eggs, and dairy products (may exclude honey)
• Macrobiotic diets exclude meat, poultry, eggs, dairy, seafood, fish (fish may be included in the diets of some macrobiotic vegetarians)

Daily Food Guide for Vegetarian Adolescents Ages 11+ Requiring 2200-2800 Kcals per Day

• Suggested daily food guide for lacto-ovo vegetarians: 9-11 servings of breads, grains, cereal, 2-3 servings of legumes, 4-5 servings of vegetables, 4 servings of fruits, 1 serving of nuts and seeds, 4 servings of milk, yogurt and cheese, 1/2-1 servings of eggs
• Suggested daily food guide for vegan vegetarians: 10-12 servings of breads, grains, cereal, 3 or more servings of legumes, 5 or more servings of vegetables, 4 or more servings of fruits, 4-6 servings of nuts and seeds, 4 servings of soy, almond or rice milk (fortified with calcium and vitamin D)

Nutrient Intake of Vegan Adolescents

• Well-planned vegetarian diets can offer many healthy advantages, especially when small amounts of animal-derived foods are consumed
• Vegans may have inadequate intakes of: protein, calcium, zinc, iron, vitamins D, B6, and B12

Total Fat and Essential Fatty Acid Intake of Vegan Adolescents

• Vegans may have inadequate intakes of total fat and essential fatty acids, especially alpha-linolenic acid
• Encourage intakes of soy products like soybean oil & soybeans, flaxseed, walnuts, tofu, walnut oil, canola oil, and eggs

Dietary Intake and Adequacy among Adolescents

• Many adolescents' diets do not match the Dietary Guidelines for Americans or the MyPyramid Recommendations
• Most have inadequate consumption of dairy, grains, fruits, and vegetables
• Data from NHANES shows the diets of adolescents consist of less than 1 serving of vegetables per day with white potatoes making up half of the vegetables
• They also consume less than 1 serving of fruits per day
• Grain intake is adequate but whole grains are less than adequate
• 32% of calories come from fat and 21% from added sugars

Percentage of Adolescents Meeting the Recommended Number of MyPyramid Servings

• Dairy products: 33% of males and 17% of females
• Fruits: 23% of males and 27% of females
• Vegetables: 35% of males and 34% of females
• Grains: 64% of males and 48% of females
• Meat: 50% of males and 17% of females

Energy and Nutrient Requirements of Adolescents

• Energy & nutrient needs during adolescence exceed those of any other point in life due to increases in lean body mass, skeletal mass, and body fat
• Needs correspond to physical maturation stage
• Dietary references intakes for selected vitamins & minerals are on Table 14.7
• Professional judgment needs to be used
• Nutrient recommendations based on chronological rather than biological development

Nutrient Intakes of Adolescents

• U.S. adolescents have inadequate intake of vitamins & minerals including folate, vitamins A, B6, C, & E, iron & zinc, magnesium, and phosphorus & calcium

Energy Requirements of Adolescents

• Energy needs are influenced by activity level, basal metabolic rate (BMR), and pubertal growth & development
• Males have a higher caloric need than females because they experience greater increases in height, weight, & lean body mass (LBM) and have a higher BMR
• Level of physicial activity declines during adolescence resulting in reduced energy requirements

Protein Requirements of Adolescents

• Protein requirements are influenced by the protein needed to maintain existing LBM and for the growth of new LBM
• DRI (Dietary Reference Intake) is 0.85 g/kg body wt
• Low protein intakes are linked to reductions in linear growth, delays in sexual maturation, and reduced LBM

Carbohydrate Requirements for Selected Nutrients of Adolescents

• 130 g/day or 45-65% of calories

Requirements for Selected Nutrients of Adolescents: Dietary Fiber

• AAP(American Academy of Pediatrics) recommends 26 g/day for adolescent females, 31 g/day for males <14 years of age, and 38 g/day for older adolescent males

Requirements for Selected Nutrients of Adolescents: Fat

• Required as dietary fat and essential fatty acids for growth and development
• 25-35% of calories from total fat
• Less than 10% of calories should come from saturated fat

Calcium Requirements for Adolescents

• Adequate calcium intake is critical to ensure peak bone mass
• Calcium absorption rate in females is highest around menarche and in males it is highest during early adolescence
• ~4 times more calcium is absorbed during early adolescence compared to early adulthood
• Adolescences who do not include dairy should consume calcium-fortified foods
• Soft drink consumption displaces nutrient-dense beverages such as milk & fortified juices

Calcium Requirements

• DRI (Dietary Reference Intake) for ages 9-18 years is 1300 mg/d
• Average intake is 865 mg for females and 1130 mg for males
• Weight-bearing activities may lead in increased bone mineral density

Iron Requirements for Adolescents

• Increased iron needs are related to rapid rate of linear growth, increase in blood volume, and menarche in females
• In females, iron needs are greatest after menarche
• In males, iron needs are greatest during the growth spurt

Iron Deficiency in Adolescents

• There is Iron deficiency vs. iron-deficiency anemia

Iron deficiency

• Determined by low serum iron, plasma ferritin & transferrin saturation, is more frequent. and often undiagnosed because of expense

Iron-deficiency anemia

• A deficiency determined by simple and inexpensive hemoglobin or hematocrit levels indicates a more advanced stage of iron deficiency, is less frequent, and is almost exclusively found in females

Estimates of iron deficiency in adolescence include

• 9% of 12-15 year old females
• 5% of 12-16 year old males
• 11% of 15-19 year old females
• 2% of 15-19 year old males

Iron Forms: Heme vs. Nonheme

• Bioavailability of iron varies by form

Heme iron

• Found in hemoglobin of animal products and is in the highly available ferrous state

Nonheme iron

• Found in plant foods & animal products and is in the less available ferric state

Vitamin D Requirements for Adolescents

• A fat-soluble vitamin that has an essential role in facilitating intestinal absorption of calcium and phosphorus and is essential for bone formation
• Synthesized by the body via skin exposure of ultraviolet B rays of sunlight
• Food sources include fatty fish, fish oils, egg yolks of hens fed Vitamin D fortified feed
• A majority comes from Vitamin D fortified foods like milk, breakfast cereals, margarines, and some juices

Folate Requirements for Adolescents

• Folate is required for DNA, RNA & protein synthesis
• DRI (Dietary Reference Intake): 400 mcg
• Severe folate deficiency leads to megaloblastic anemia
• Severe deficiency is rare, but inadequate folate status appears to be more common
• Folate added to fortified foods is better absorbed than folate from natural foods
• Adequate folate intake for female adolescents reduces incidence of birth defects like spina bifida
• It's imperative that women of reproductive age (15 to 44 years) consume adequate folic acid
• Increased risk of folate deficiency is associated with skipping breakfast and not consuming orange juice or fortified cereals

Vitamin C Requirements for Adolescents

• Marginal adequacy among adolescents
• It's involved in the synthesis of collagen and other connective tissues
• Acts as an antioxidant
• Smoking ↑ need for Vitamin C

Physical Activity and Sports

• Physical activity encompasses any bodily movement produced by skeletal muscles that results in energy expenditure
• Exercise-a subset of physical activity that is planned, structured, & repetitive & done to maintain physical fitness
• Physical fitness involves a set of attributes that are either health or skill related

Benefit of Physical Activity

• Regular physical activity leads to improved aerobic endurance & muscle strength, a reduced risk of obesity, greater bone density , positive self-esteem & self-concept, and lower levels of anxiety & stress

Recommendations on Physical Activity

• The Physical Activities Guidelines for Americans recommend adolescents to be physically active every day, engage in 60 minutes or more of physical activity, and include muscle- and bone-strengthening activities at least 3 days a week

Factors Affecting Physical Activity

• Adolescents are more likely to be physically active if they have confidence in their ability to exercise, positive perceptions of activity or sports, positive attitudes toward activity, and peer & family support

Adolescent nutrition focuses on meeting the needs during puberty through healthy eating. Needs are based on biological maturity, not age. Common unhealthy behaviors include dieting and skipping meals, while health-enhancing behaviors involve healthful eating and physical activity.