A 7-day-old male infant presents to the pediatrician for weight loss. There is no history of excessive crying, irritability, lethargy, or feeding difficulty. The parents deny any history of fast breathing, bluish discoloration of lips/nails, fever, vomiting, diarrhea, or seizures. He was born at full term by vaginal delivery without any perinatal complications and his birth weight was 3.6 kg (8 lb). Since birth he has been exclusively breastfed and passes urine six to eight times a day. His physical examination, including vital signs, is completely normal. His weight is 3.3 kg (7.3 lb); length and head circumference are normal for his age and sex. Which of the following is the next best step in the management of the infant?

Evaluation of the mother for malnutrition

Admission of the infant in the NICU to treat with empiric intravenous antibiotics

Emphasize the need to clothe the infant warmly to prevent hypothermia

Supplementation of breastfeeding with an appropriate infant formula

A 24-year-old woman comes to the physician for preconceptional advice. She has been married for 2 years and would like to conceive within the next year. Menses occur at regular 30-day intervals and last 4 days with normal flow. She does not smoke or drink alcohol and follows a balanced diet. She takes no medications. She is 160 cm (5 ft 3 in) tall and weighs 55 kg (121 lb); BMI is 21.5 kg/m2. Physical examination, including pelvic examination, shows no abnormalities. She has adequate knowledge of the fertile days of her menstrual cycle. Which of the following is most appropriate recommendation for this patient at this time?

Begin high-dose vitamin A supplementation

Begin vitamin B12 supplementation

A 3-month-old African American boy presents to his pediatrician’s office for his routine well visit. He was born full-term from an uncomplicated vaginal delivery. He is exclusively breastfeeding and not receiving any medications or supplements. Today, his parents report no issues or concerns with their child. He is lifting his head for brief periods and smiling. He has received only 2 hepatitis B vaccines. Which of the following is the correct advice for this patient’s parents?

He should start vitamin D supplementation.

He should have his serum lead level checked to screen for lead intoxication.

He needs a 3rd hepatitis B vaccine.

A 17-year-old girl is brought in by her mother due to rapid weight loss over the past month. The patient says she has been having episodes of diarrhea, which she attributes to laxatives she takes regularly to keep her weight down. She also says she has not had her period yet. The patient’s mother adds that the patient has been underperforming at school and acting very strangely at home. Her current BMI is 16.8 kg/m2. On physical examination, the skin on her limbs and around her neck is inflamed and erythematous. Her tongue is bright red and smooth. She states that over the last 2 weeks, she has been eating nothing but small portions of fruit. She is diagnosed with a vitamin deficiency. Which of the following statements is true about the vitamin most likely deficient in this patient?

Synthesis requires vitamin B2 and B6

It increases the GI absorption of iron

Synthesis requires vitamin B1 and B6

It is used to treat hypertension

A 69-year-old man is brought to the emergency room by his daughter due to confusion. She reports that her father did not remember who she was yesterday, and his refrigerator was completely empty when she tried to make him lunch. She states that he was acting like himself when she visited him last week. She also notes that he has struggled with alcoholism for many years and has not seen a doctor in over two decades. She is unsure if he has any other chronic medical conditions. In the emergency room, the patient’s temperature is 101.2°F (38.4°C), pulse is 103/min, respirations are 22/min, and O2 saturation is 92% on room air. His BMI is 17.1 kg/m^2. Physical exam reveals an extremely thin and frail man who is not oriented to person, place, or time. As he is being examined, he becomes unresponsive and desaturates to 84%. He is intubated and admitted to the intensive care unit for what is found to be pneumonia, and the patient is started on total parental nutrition as he is sedated and has a history of aspiration from a prior hospitalization. Two days later, physical exam is notable for new peripheral edema. Laboratory tests at that time reveal the following: Serum: Na+: 133 mEq/L Cl-: 101 mEq/L K+: 2.4 mEq/L HCO3-: 24 mEq/L BUN: 22 mg/dL Glucose: 124 mg/dL Creatinine: 1.1 mg/dL Phosphate: 1.1 mg/dL Mg2+: 1.0 mg/dL Which of the following could have prevented the complication seen in this patient?

Slow initiation of total parenteral nutrition (TPN)

Initiation of intermittent dialysis

A 66-year-old man weighing 50 kg (110 lb) is admitted to the hospital because of sepsis complicated by acute respiratory distress syndrome. The physician decides to initiate total parenteral nutrition and prescribes short-term hypocaloric intake of 20 kcal/kg/day with 20% of the total energy requirement provided by proteins and 30% provided by fats. The physician calculates that a total volume of 1100 mL/day should be infused during the parenteral nutrition therapy to maintain fluid balance. A colloid containing 10 g/dL of albumin and an emulsion with a fat concentration of 33 g/dL are used to prepare parenteral nutrition modules. Which of the following is the most appropriate module to meet the carbohydrate requirement in this patient over the next 24 hours?

500 mL of 25% dextrose solution

750 mL of 25% dextrose solution

750 mL of 10% dextrose solution

500 mL of 10% dextrose solution

250 mL of 50% dextrose solution

Childhood nutrition requirements by age for USMLE Step 2 CK: High-Yield Pediatrics Lessons

Infant Nutrition (0-12mo) - Foundation Fuel

Energy: Approx. 100 kcal/kg/day.
- 0-6 mo: 108 kcal/kg/day
- 6-12 mo: 98 kcal/kg/day
Protein: 2.2 g/kg/day (0-6mo) → 1.2 g/kg/day (6-12mo).
Supplementation (for exclusively breastfed infants):
- Vitamin D: 400 IU/day starting from birth.
- Iron: 1 mg/kg/day from 4 months until iron-rich complementary foods are introduced.

⭐ Human milk and most formulas provide 65-70 kcal/100ml. Colostrum is lower in calories but richer in protein and secretory IgA.

Infant Feeding Guidelines: Birth to 12 Months

Feeding Flow:

Toddler/Preschool (1-5y) - Picky Eater Playbook

Energy: Approx. 80 kcal/kg/day.
Protein: 1.2 g/kg/day.
Picky Eating (Neophobia) is common. Management principles:
- Offer small, nutrient-dense portions.
- Repeat exposure to new foods (10-15 times).
- Avoid force-feeding; maintain a positive mealtime environment.
- Limit milk intake to <500 mL/day to prevent displacing iron-rich foods.

Picky Eater Swaps: Vegetable Alternatives and Tips

⭐ Physiologic Anorexia: A normal decrease in appetite around 1 year of age due to a slower growth rate. Reassure parents.

School-Age Child (6-12y) - Growth & Grind

Growth Pattern: Steady, latent period before the adolescent spurt. Average gain: ~3-3.5 kg/year and ~6-7 cm/year.
Caloric Needs: 1600-2200 kcal/day, varying with physical activity.
Macronutrients:
- Protein: ~0.95 g/kg/day.
- Carbohydrates: Main energy source for active lifestyles.
Key Micronutrients:
- Calcium: Crucial for bone mineralization; requirement is 1000 mg/day.
- Iron & Iodine: Essential for cognition, attention, and preventing deficiency anemia.

⭐ Iron deficiency, even without anemia, is linked to poor concentration and reduced academic performance in this age group.

Food groups for a balanced diet

Adolescent Nutrition (13-18y) - The Final Spurt

Final growth spurt demands peak nutritional support. Requirements diverge significantly based on gender due to differences in body composition and physiological changes.

Macronutrient Needs: Gender-specific recommendations reflect differing metabolic rates and muscle mass development.

Nutrient	Boys (14-18y)	Girls (14-18y)
Energy	~2800 kcal/d	~2200 kcal/d
Protein	~52 g/d	~46 g/d
Iron	11 mg/d	15 mg/d
Calcium	1300 mg/d	1300 mg/d

-   **Calcium:** Essential for attaining peak bone mass. **~45%** of adult skeletal mass is built during adolescence.
-   **Zinc:** Vital for sexual maturation & protein synthesis.

⭐ Iron needs for adolescent girls (15 mg/d) are higher than for boys (11 mg/d) primarily to replace menstrual losses, making them a high-risk group for iron-deficiency anemia.

Exclusive breastfeeding is recommended for the first 6 months of life, continuing alongside complementary foods.

Initiate complementary feeding at 6 months; not before 4 months or after 6 months.

Infant energy needs are the highest (~100 kcal/kg/day), which gradually decrease with age.

Protein requirement is highest in infancy (~1.5 g/kg/day) and then declines.

Iron supplementation is vital after 6 months, especially in breastfed infants.

Routine Vitamin D (400 IU/day) is recommended for all infants, particularly those who are breastfed.

Avoid cow's milk before 1 year due to its low iron content and high renal solute load.

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