Nutrition

Michael R. Kohn

Nutrition is an essential component of adolescent and young adult (AYA) health care. Optimal nutrition assists in reaching the potential for physical growth, development, and the prevention of illness. Two important transformations occur during adolescence that change nutritional needs. Growth and changes in body composition are greater and more rapid than at any other time in life, except infancy. In general, there is also a significant change in the adolescent’s eating habits and food consumption. Adolescents typically reduce regular breakfast consumption, increase consumption of prepared foods, snacks, fried foods, nutrient-poor foods, and sweetened beverages, and have a significant increase in portion size at each meal. This is associated with a decrease in the consumption of dairy products, fruits, and vegetables. Sodium intake is far in excess of recommended levels, whereas calcium and potassium intakes are below recommended levels.¹ The nutritional needs of young adults differ from both adolescents and the average population values.²,³

Health care providers should assess nutritional status and provide appropriate nutritional counseling as part of health supervision visits. Information quantifying nutritional requirements and providing illustration of healthy eating information are available at http://circ.ahajournals.org/content/112/13/2061.full. Further assistance for families to provide nutritious, balanced meals is available from the US Department of Agriculture (USDA) MyPlate site (http://kidshealth.org/parent/nutrition_center/healthy_eating/myplate.html). MyPlate includes sections for vegetables, fruits, grains, and foods high in protein. MyPlate’s user-friendly, interactive Web site provides simple messages for parents (Fig. 6.1).

POTENTIAL NUTRITIONAL PROBLEMS

The National Health and Nutrition Examination Survey (NHANES) (http://www.cdc.gov/nchs/nhanes/about_nhanes.htm) concluded that the highest prevalence of unsatisfactory nutritional status occurs in the adolescent age-group. Of particular note were deficiencies in the intake of calcium, iron, riboflavin, thiamine, and vitamins A and C.

Risk Factors

Increased nutritional needs during adolescence are related to several factors.

Adolescents gain 20% of their adult height.

Adolescents gain 50% of their adult skeletal mass.

FIGURE 6.1 The My Plate site provides a range of healthy eating strategies and advice for professionals and consumers. (From the USDA Center for Nutrition Policy and Promotion’s ChooseMyPlate.gov Web site.)

Caloric and protein requirements are maximal.
Specific nutrient needs—gender, chronic illness.

Increased physical activity of AYAs makes proper nutrition essential.
Poor eating habits of AYAs contribute to nutritional problems.⁴,⁵
- Missed meals are common.
- High-energy snacks of low nutritional value are popular.
- Peer pressure leads to changes in a range of eating behaviors, including restrictive and overeating patterns and purging behaviors.
- The adolescent’s family may exhibit poor eating habits, and meal preparation may be inadequate.
- Inadequate financial resources to purchase food or to prepare nutritious meals.
In AYAs, dietary choices contribute to increased risk for cardiovascular disease.
- Low fruit and vegetable consumption and high sweetened beverage consumption are independently associated with the prevalence of metabolic syndrome in specific sex-ethnicity populations.
- High-fiber diets may protect against obesity and cardiovascular disease by lowering insulin levels.

NUTRITIONAL ASSESSMENT

Assessing the nutritional status of an adolescent or young adult should be part of a comprehensive health evaluation. This becomes even more important in AYAs who are identified as nutritionally at risk. Such young people include those with nutritionally related medical conditions, dietary deficiencies, or those with conditions that predispose them to inadequate nutrition. Nutritional assessment requires repeated measurements of nutritional status over time. Methods used in the nutritional assessment of adolescents include dietary and clinical evaluation, measurements of body composition, and obtaining laboratory data.

Dietary Data

There is a range of validated strategies used to obtain dietary data from AYAs. These include food records, 24-hour recall of all food consumed, food frequency questionnaires, and other questionnaires (http://appliedresearch.cancer.gov/assess_wc/review/agegroups/adolescents/validation.html?&url=/tools/children/review/agegroups/adolescents/validation.html).

An example of screening questions that are quick and easy to ask includes the following:

How many meals do you usually eat in a day? Any snacks?
Tell me everything you have eaten in the past 24 hours.
Are there any foods that you have eliminated from your diet?
Are you on a diet?
Are you comfortable with your eating habits?
Do you ever eat in secret? Do you ever feel you can’t stop eating?
Have you recently lost or gained weight, or has your weight stayed the same?
Do you feel that your weight is too much, too little, or about right?
What is the most you have ever weighed, and what would you like to weigh?

Helpful screening questions for AYAs (followed by the associated sensitivity and specificity for disordered eating in adolescence) include the following⁶:

How many diets have you been on in the past year? (Two or three diets, 88% sensitivity and 63% specificity; four or five diets, 69% sensitivity and 86% specificity).
Do you feel you should be dieting? (Often, 94% sensitivity and 67% specificity; usually, 87% sensitivity and 82% specificity).
Do you feel dissatisfied with your body size? (Often, 96% sensitivity and 61% specificity; usually, 88% sensitivity and 74% specificity).
Does your weight affect the way you feel about yourself? (Often, 97% sensitivity and 61% specificity; usually, 91% sensitivity and 74% specificity).

Each of these questions appears to have a very high correlation with the score on the Eating Attitudes Test (EAT-26).⁷ This screening test examines attitudes and behaviors regarding food, weight, and body image and has been validated for use in AYAs.

Clinical Signs of Nutritional Deficiencies

Please see Table 6.1.

Anthropometric Measurements

Weight and height: Weight-for-age and height-for-age charts can be obtained from the Centers for Disease Control Prevention (CDC) on their Web site at http://www.cdc.gov/growthcharts/.
Body mass index is a very useful screening tool, but it has its limitations. See Chapter 32 on Obesity.
Skin fold measurements and waist-hip ratio all provide valuable information in a nutritional assessment. These measurements can assist in quantifying obesity and have shown to have predictive value with respect to health outcomes such as cardiovascular disease and insulin resistance. They are not, however, currently recommended for clinical use because they require specific training to perform accurately.

TABLE 6.1 Clinical Signs of Nutritional Deficiency

Body Parts	Nutritional Deficiency	Clinical Signs of Deficiency
Skin	Iron Vitamin A Hyperlipidemia Vitamin C Vitamin K, C, and folate	Pallor Follicular hyperkeratosis Xanthoma Petechiae Bruising and purpura
Eyes	Riboflavin, niacin Vitamin A	Angular palpebritis Night blindness
Lips	Riboflavin, niacin	Angular stomatitis Cheilosis
Tongue	Niacin, folic acid, vitamins B₆ and B₁₂	Glossitis
	Niacin, folic acid, vitamins B₆ and B_12, or iron	Papillary atrophy
	Zinc	Loss of taste
Gums	Vitamin C	Hypertrophy, bleeding
Teeth	Diet high in refined sugars	Cavities
Hair	Protein energy malnutrition	Dry, dull, brittle
Neck	Iodine	Goiter
Nails	Malnutrition, iron, or calcium	Brittle with frayed borders
	Vitamin A	Concave or eggshell
Bones and Joints	Vitamin D Vitamin C	Rickets Scurvy

Laboratory Tests

Laboratory tests helpful in assessing nutritional status include hemoglobin, hematocrit, ferritin, serum protein, albumin, and vitamins D, B₁₂, and folate.

Nutritional Requirements

Dietary reference intakes (DRIs) represent quantitative estimates of nutrients used to plan and evaluate diets for healthy people, including AYAs. The DRIs are a set of four nutrient reference values.

Recommended dietary allowance (RDA): This is the dietary intake level that is sufficient to meet the nutrient requirements of almost all healthy individuals (97% to 98%) in the United States.
Adequate intake (AI): This is the value based on observed or experimentally determined approximations of nutrient intake by a group—used when RDA cannot be determined.
Estimated average requirement (EAR): This is the intake value that is estimated to meet the requirement defined by a specified indicator of adequacy in 50% of an age- and gender-specific group. At this level of intake, the remaining 50% of the specified group would not have its needs met.
Tolerable upper intake level (UL): This is the maximum level of daily nutrient intake that is unlikely to pose risks of adverse health effects to almost all of the individuals in the group for whom it is designed.

The DRIs cover the following groups of nutrients:

Calcium, vitamin D, phosphorus, magnesium, and fluoride
Folate and other B vitamins
Antioxidants (e.g., vitamin C, vitamin E, selenium)
Macronutrients (e.g., proteins, fats, carbohydrates)
Trace elements (e.g., iron, zinc)
Electrolytes and water
Other food components (e.g., fiber, phytoestrogens)

The requirements are reported to differ slightly between AYAs (between 19 and 30 years of age). Details of the recommended DRIs definitions are available at http://www.hc-sc.gc.ca/fn-an/alt_formats/hpfb-dgpsa/pdf/nutrition/dri_tables-eng.pdf.

Energy Requirements

Energy requirements are determined by basal metabolic rate, growth status, physical activity, and body composition. Energy requirements of adolescents vary depending on the timing of growth and pubertal development. As such, energy needs are based on height because it provides a better estimate of total daily caloric recommendations. Suggested caloric intakes are listed in Table 6.2.

Protein

Protein provides 4 kcal of energy in each gram. Protein requirements are based on the amount of protein needed to maintain existing lean body mass and the increase in additional lean body mass with growth and development. Protein requirements are highest during the peak height velocity. In the populations surveyed in the United States, most AYA diets exceed the RDA for protein.

Carbohydrates

Carbohydrates provide 4 kcal of energy in each gram. Carbohydrates should make up approximately 50% of the daily caloric intake. However, no more than 10% to 25% of calories should come from sweeteners (sucrose and high-fructose corn syrup). Nearly, 12% of carbohydrates consumed by AYAs come from the added sweeteners in soft drinks.

Carbohydrate-containing foods include grain products, fruits, and vegetables. Approximately 25 to 35 g of fiber should be consumed daily. Fiber is found in whole grain foods, fruits, vegetables, legumes, nuts, and seeds.

Glycemic index (GI) classifies carbohydrate foods on the basis of the effect on blood glucose. The index ranges from 0 to 100, with glucose or other reference standard being 100. Hence, the lower the GI, the lower the expected rise in blood sugar for a given food. In general, foods are classified into low GI (<40), moderate GI (40 to 70), and high GI (>70).

TABLE 6.2 Recommended Dietary Allowances for AYAs

		Male (y)			Female (y)
Category		11-14	15-18	19-24	11-14	15-18	19-24	Pregnancy	Lactating (first 6 mo)	Lactating (second 6 mo)
Weight (kg)		45	66	72	46	55	58
Height (cm)		157	176	177	157	163	164
Energy (cal)		2,500	3,000	2,900	2,200	2,200	2,200	+300	+500	+500
Protein (g)		45	59	58	46	44	46	60	65	62
Minerals
	Iron (mg/d)	12	12	10	15	15	15	30	15	15
	Zinc (mg/d)	15	15	15	12	12	12	15	19	16
	Iodine (µg/d)	150	150	150	150	150	150	175	200	200
Vitamins
	Vitamin A (IU)	10	10	10	10	10	10	10	10	10
Adapted from Food and Nutrition Board, National Research Council. Recommended dietary allowances. 10th ed. Washington, DC: National Academy Press, 1989.