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Chapter 14
Adolescent Nutrition
Nutrition Through the Life Cycle
Judith E. Brown
Vegetarian Diets during
Adolescence
• About 4% of adolescents report following a
vegetarian diet
• Reasons adolescents adopt a vegetarian diets
include:
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Cultural or religious beliefs
Moral or ethical concerns
Health beliefs
To restrict fat and/or calories
A means of independence from family
Types of Vegetarian Diets and
Food Excluded
Nutrient Intake of Vegan
Adolescents
• Well-planned vegetarian diets can offer
many healthy advantages
– Best when small amounts of animal-derived
foods
• Vegans may have inadequate intakes
– Protein
– Calcium, Zinc, and Iron
– Vitamins D, B6, and B12
Total Fat and Essential Fatty
Acid Intake of Vegan
Adolescents
• Vegans may have inadequate intakes
– Total fat
– Essential fatty acids especially alpha-linolenic
acid
• Encourage intakes of
– Soy products: Soybean oil & Soybeans
– Flaxseed, Walnuts, Tofu
– Walnut oil, Canola oil
– Eggs
Nutritional Needs in a Time of
Change
• Health-compromising eating behaviors
– Excessive dieting
– Meal skipping
– Use of unconventional nutritional and
nonnutritional supplements
– Fad diets
Nutritional Needs in a Time of
Change
• 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 ht & wt
– Accumulation of skeletal mass
– Changes in body composition
• The sequence of maturation events is consistent
but great individual variation in age of maturation
Normal Physical Growth and
Development
• Variations in reaching sexual maturity
affect 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 or
“Tanner Stages”
• Sexual Maturation Rating (SMR) (a.k.a.
“Tanner Stages”)—scale of secondary
sexual characteristics used to assess degree
of pubertal maturation
– SMR 1=prepuburtal 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 great deal of variation in
chronological age at which sexual
maturation takes place
• Peak velocity of linear growth occurs
during SMR 4 & ends with 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 wt gain at the same time
– Peak linear growth &
– Peak muscle mass accumulation
• Peak wt gain, ~20 lb per year
• Body fat decreases to ~12%
• ~Half of bone mass is accrued in
adolescence
Normal Psychosocial
Development
• Adolescents develop:
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A sense of personal identity
A moral & ethical value system
Feelings of self-esteem or self-worth
A vision of occupational aspirations
Normal Psychosocial
Development
• Three periods of psychosocial development:
– Early adolescence (11 to 14)
– Middle adolescence (15 to 17)
– Late adolescence (18 to 21)
Normal Psychosocial
Development
• The need to fit in can affect nutritional
intake
– Who they eat with
– Where they eat
• Peer influences may be greater than family
– May improve dietary intake
– May lead to poor dietary intake
Health and Eating-related
Behaviors during Adolescence
• Factors affecting eating behaviors
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Peer influence
Parental modeling
Food availability, preferences, & cost
Personal & cultural beliefs
Mass media
Body image
Conceptual Model for Factors Influencing
Eating Behavior of Adolescents
Health and Eating-related
Behaviors during Adolescence
• The model depicts 3 interacting levels of
influence on adolescent eating behaviors
– Personal or individual
– Environmental
– Macrosystem
Health and Eating-related
Behaviors during Adolescence
• Busy lives lead to different eating styles
– Little time to sit down for a meal
– Snacking and meal skipping common
– Eating away from home and at fast-food
restaurants
– Consuming more soft drinks, less nutrient
dense drinks
– Eating meals in front of the television
Dietary Intake and Adequacy
among Adolescents
• Many adolescents have diets that do not
match the Dietary Guidelines for Americans
or the MyPyramid Recommendations
• Most have inadequate consumption of:
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Dairy
Grains
Fruits
Vegetables
Dietary Intake and Adequacy
among Adolescents
• Data from NHANES-adolescents’ diets consist of
– Less than 1 serving of vegetables per day
• White potatoes make up half of the vegetables
– Less than 1 serving fruits per day
– Adequate intake of grains but whole grains less
than adequate
– 32% of calories from fat & 21% from added
sugars
Percentage of Adolescents
Meeting the Recommended
Number of MyPyramid Servings
Energy and Nutrient
Requirements of Adolescents
• Increases in lean body mass, skeletal mass
and body fat
• Energy & nutrient needs during adolescence
exceed those of any other point in life
• Needs correspond to physical maturation
stage
Energy and Nutrient
Requirements of Adolescents
• 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:
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Folate
Vitamins A, B6, C, & E
Iron & zinc
Magnesium
Phosphorus & calcium
Nutrient
Intakes of
Adolescent
s
Energy Requirements of
Adolescents
• Energy needs are influenced by:
– Activity level
– Basal metabolic rate (BMR)
– Pubertal growth & development
• Because males have greater increases in ht, wt, &
lean body mass (LBM) & higher BMR, they have
a higher caloric need than females
• Level of physical activity declines during
adolescence resulting in reduced energy
requirements
Protein Requirements of
Adolescents
• Protein requirements influenced by protein
needed:
– To maintain existing LBM
– For growth of new LBM
• DRI is 0.85 g/kg body wt
• Low protein intakes linked to:
– Reductions in linear growth
– Delays in sexual maturation
– Reduced LBM
Requirements for Selected
Nutrients of Adolescents
• Carbohydrates:
– 130 g/day or 45-65% of calories
• Dietary Fiber:
– AAP recommends
• 26 g/day for adolescent females
• 31 g/day for males <14 years of age
• 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
– <10% calories from saturated fat
Calcium Requirements for
Adolescents
• Adequate intake of calcium is critical to
ensure peak bone mass
• Calcium absorption rate in females is
highest around menarche
• Calcium absorption rate in males highest
during early adolescence
Calcium Requirements for
Adolescents
• ~4 times more calcium absorbed during
early adolescence compared to early
adulthood
• Adolescences who do not include dairy
should consume calcium-fortified foods
• Soft drink consumption displaces nutrientdense beverages such as milk & fortified
juices
Calcium Requirements for
Adolescents
• DRI for ages 9-18 years is 1300 mg/d
• Average intake is:
– 865 mg for females
– 1130 mg for males
• Weight-bearing activities may lead in
increased bone mineral density
Iron Requirements for
Adolescents
• Increased iron needs related to:
– Rapid rate of linear growth
– Increase in blood volume
– Menarche in females
• In females, iron needs greatest after
menarche
• In males, iron needs greatest during the
growth spurt
Iron Deficiency in Adolescents
• Iron deficiency vs. iron-deficiency anemia
– Iron deficiency
• Determined by low serum iron, plasma ferritin &
transferrin saturation
• Iron deficiency more frequent
• Often undiagnosed because of expense
Iron Deficiency in Adolescents
• Iron deficiency vs. iron-deficiency anemia
– Iron-deficiency anemia
• Determined by simple and inexpensive hemoglobin
or hematocrit levels
• Indicates more advanced stage of iron deficiency
• Less frequent but almost exclusively females
Iron Deficiency in Adolescents
• Estimates of iron deficiency:
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9% of 12-15 y/o females
5% of 12-16 y/o males
11% of 15-19 y/o females
2% of 15-19 y/o males
Vitamin D Requirements for
Adolescents
• Vitamin D-fat soluble:
– Essential role in facilitating intestinal absorption of
calcium and phosphorus
– Essential for bone formation
– Synthesized by the body via skin exposure of
ultraviolet B rays of sunlight
– Food sources: fatty fish, fish oils, egg yolks of hens fed
Vitamin D fortified feed
– Majority of Vitamin D from Vitamin D fortified foods
(milk, breakfast cereals, margarines, and some juices)
Folate Requirements for
Adolescents
• Folate required for DNA, RNA & protein
synthesis
• DRI: 400 mcg
• Severe folate deficiency leads to
megaloblastic anemia
• Severe deficiency rare but inadequate folate
status appears to be more common
Folate Requirements for
Adolescents
• 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
Folate Requirements for
Adolescents
• It is imperative that women of reproductive
age (15 to 44 years) consume adequate folic
acid
• Increased risk of folate deficiency
– Skipping breakfast
– Not consuming orange juice or fortified cereals
Vitamin C Requirements for
Adolescents
• Vitamin C—marginally adequate among
adolescents
• Involved in the synthesis of collagen and
other connective tissues
• Acts as an antioxidant
• Smoking  need for Vitamin C
Nutrition Screening, Assessment,
and Intervention
• The AMA recommends all adolescents receive annual
health screening & guidance
• Screening should include:
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Wt, ht, & BMI
Disordered eating tendencies
Blood lipid levels
Blood pressure
Iron status (hemoglobin/hematocrit)
Food security/insecurity
Dietary intake/adequacy
Nutrition Screening, Assessment,
and Intervention
• Nutrition screening should include a brief dietary
assessment
– Food frequency questionnaires
– 24-hour recalls
– Food diaries or Food Records
• Table 14.12 lists the advantages and disadvantages
of each dietary assessment method
• Table 14.13 lists the nutrition risk indicators that
may warrant further assessment and counseling
Nutrition Education and
Counseling
• Considerations when educating &
counseling adolescents:
1) Initial component of session should
involve:
– Getting to know adolescent, including personal
health or nutrition-related concerns
– Providing overview of events & content of
counseling session
Nutrition Education and
Counseling
• Considerations when educating &
counseling adolescents (cont.):
2) Involve adolescent in decision-making
process
3) Encourage adolescent to suggest ways to
change
4) Work toward only 1 or 2 goals per
counseling session
Nutrition Education and
Counseling
• Use of technology to facilitate education and
counseling
– Text messaging
– Podcasts
– YouTube
– Facebook
– Twitter
• Technology can serve as a means to convey
nutrition info in an engaging way
Physical Activity and Sports
• Physical activity—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—set of attributes that are
either health or skill related
Benefit of Physical Activity
• Regular physical activity leads to:
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Improved aerobic endurance & muscle strength
Reduced risk of obesity
Greater bone density
Positive self-esteem & self-concept
Lower levels of anxiety & stress
Recommendations on Physical
Activity
• The Physical Activities Guidelines for
Americans recommend adolescents:
– Be physically active every day
– Engage in 60 minutes or more physical activity
– Include muscle- and bone-strengthening
activities at least 3 days a week
Physical Activity Practices of
U.S. Adolescents
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Only 35% met activity guidelines
25% reported no moderate to vigorous activity
Activity declines throughout adolescence
More males than females meet daily activity
guidelines
• More white teens than African or Mexican
American teens meet activity guidelines
Factors Affecting Physical
Activity
• Adolescents more likely to be physically activity
if they have:
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Confidence in ability to exercise
Positive perceptions of activity or sports
Positive attitudes toward activity
Peer & family support
Nutritional Considerations for
Physically Active Adolescents
• High levels of activity combined with
growth & development increase needs for
energy, protein & certain vitamins &
minerals
• Nutrient needs higher during intense
training & competition seasons
• Monitor changes in body weight to assess
for adequate energy and protein intake
Nutritional Considerations for
Physically Active Adolescents
• Competitive athletes may need 500-1500
additional calories per day
• Protein should supply no more than 30% of
calories in the diet
• Special concern for vegetarian athletes or
restricted caloric intake to maintain a
particular weight
Promoting Healthy Eating and
Physical Activity Behaviors
• Effective nutrition messages for youth
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Teens are “present oriented”
Concerned about appearance
Achieving maintaining a healthy wt
Having lots of energy
Optimizing sports performance
Environmental or moral aspects of food
Promoting Healthy Eating and
Physical Activity Behaviors
• Parent involvement
• Target parents
• They are gatekeepers of foods
• Serve as role models
• Teenagers eat based on availability and
convenience
• Parents can capitalize on this
• Stock a variety of nutritious ready-to-eat foods
Nutrition Education
in Schools
• Nutrition instruction required by 67% of
middle schools & 72% of high schools
• Most nutrition is offered in health education
courses
• Nutrition education to health ed teachers
has  from 43% to 65% from 2000 to 2006
School Wellness Policies
• All school districts with a federally-funded
school meals program must have a wellness
policy that addresses nutrition & physical
activity
Model Nutrition Program
• Numerous innovative nutrition programs
exist that promote nutrition to youth
• One example is CANfit (California
Adolescent Nutrition & Fitness)
• Visit the CANfit website at:
http://www.canfit.org/