Nutritional Requirements & Micronutrients

Forfar & Arneil 7th Edition · Dietary reference values · Energy · Proteins · Fats · Carbohydrates · Vitamins (A, B, C, D, E, K) · Minerals (iron, calcium, zinc, iodine, selenium)
📌 Key principles: Growth and development depend on adequate macro- and micronutrients. Energy needs vary by age, activity, growth rate. Protein quality matters (essential amino acids). Fat provides essential fatty acids and energy. Vitamins and minerals have specific functions; deficiencies cause distinct clinical syndromes.

📖 Nutritional requirements & micronutrients in children

📊 Dietary Reference Values (DRVs)
Estimated Average Requirement (EAR), Reference Nutrient Intake (RNI), Lower Reference Nutrient Intake (LRNI). RNI meets needs of 97.5% of population. Used for planning diets.
⚡ Energy requirements
Infants: ~85-100 kcal/kg/day. Children: decrease with age. Adolescents: increase during growth spurt. Factors: BMR, physical activity, growth, thermogenesis.
🥩 Protein & amino acids
Essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine. Children need higher protein per kg than adults (1.0-1.5 g/kg/day).
🧈 Fats (lipids)
Essential fatty acids: linoleic acid (omega-6), alpha-linolenic acid (omega-3). Required for brain development, retinal function. Long-chain PUFA (DHA, AA) in breast milk.
🍞 Carbohydrates
Primary energy source. Complex > simple sugars. Fibre important for bowel health. Lactose main carb in milk. Avoid added sugars <2 years.
📊 Key vitamins & minerals: Vitamin A (vision, immunity), D (bone, calcium absorption), E (antioxidant), K (clotting), B complex (energy metabolism), C (collagen, antioxidant), Iron (Hb, cognition), Calcium (bone), Zinc (growth, immunity), Iodine (thyroid), Selenium (antioxidant).

🔍 Clinical approach to assessing nutritional status

1
Anthropometric measurements – Weight, length/height, head circumference (<2y), MUAC. Calculate weight-for-length (under 2y) or BMI (≥2y). Plot on WHO growth standards.
2
Dietary assessment – 24-hour recall, food diary (3-7 days), breastfeeding frequency, formula amounts, portion sizes. Identify energy, protein, micronutrient gaps.
3
Clinical examination for deficiencies – Pallor (iron/B12), glossitis/angular stomatitis (B vitamins/iron), koilonychia (iron), rickets (vitamin D), xerophthalmia (vitamin A), bleeding (vitamin K), periorificial rash (zinc).
4
Laboratory investigations – FBC, ferritin, iron studies, zinc, 25-OHD, B12, folate, vitamin A (retinol). CRP to interpret acute phase reactants.
5
Identify risk factors – Prematurity, low birth weight, exclusive breastfeeding >6 months without supplements, restrictive diets (vegan, dairy-free), malabsorption (celiac, CF), chronic disease.
6
Growth monitoring – Serial measurements. Faltering growth: weight crossing >2 centile lines. Rapid weight gain: crossing >2 centile lines upward (obesity risk).
📌 Clinical pearl: The Reference Nutrient Intake (RNI) is the amount sufficient for 97.5% of the population. For iron, RNI for infants 6-12 months is 7.7 mg/day (UK). Breast milk iron is low but bioavailable; supplementation recommended after 4-6 months.

📋 Stepwise management of nutritional deficiencies & optimisation

1
Iron deficiency anaemia – Oral ferrous sulphate 3-6 mg/kg/day (elemental iron). Continue for 3 months after Hb normalises. Dietary advice: red meat, fortified cereals, legumes; limit cow's milk.
2
Vitamin D deficiency – Stoss therapy: 150,000-300,000 IU vitamin D orally once, or 2000-4000 IU/day for 3 months. Maintenance 400 IU/day. Treat hypocalcaemia with calcium.
3
Vitamin A deficiency (xerophthalmia) – High-dose vitamin A: 200,000 IU (12-59 months) orally immediately, next day, then at least 2 weeks later. Prevent with 6-monthly supplementation in endemic areas.
4
Zinc deficiency – Oral zinc sulphate 1-2 mg/kg/day (elemental zinc). Treat underlying malabsorption (acrodermatitis enteropathica requires lifelong zinc).
5
Protein-energy malnutrition (PEM) – Severe acute malnutrition: WHO 10 steps, F-75 then F-100/RUTF. Marasmus: high-energy feeds. Kwashiorkor: cautious protein reintroduction.
6
Breastfeeding & complementary feeding advice – Exclusive breastfeeding 6 months. Introduce iron-rich complementary foods from 6 months. Vitamin D for all breastfed infants. Limit added sugar and salt.
⚠️ Important definitions: EAR = Estimated Average Requirement (meets 50%). RNI = Reference Nutrient Intake (97.5%). LRNI = Lower Reference Nutrient Intake (2.5%). Safe intake used when insufficient data.

🧠 Reflex prompts: nutritional requirements & micronutrients

🍼 A 6-month-old exclusively breastfed infant. What supplements are recommended?
Vitamin D 400 IU daily. Iron 1 mg/kg/day from 4-6 months (AAP). Continue breastfeeding alongside solids.
🩸 A 9-month-old with microcytic anaemia, pica. Which nutrient deficiency?
Iron deficiency. Most common micronutrient deficiency worldwide. Ferrous sulphate 3-6 mg/kg/day.
🦴 A 12-month-old with bowed legs, rachitic rosary, hypocalcaemia. Which vitamin deficiency?
Vitamin D deficiency rickets. Low 25-OHD. Stoss vitamin D + calcium.
👁️ A 3-year-old with night blindness, Bitot spots, corneal xerosis. Which deficiency?
Vitamin A deficiency. High-dose vitamin A (200,000 IU) stat, next day, then 2 weeks later.
🧪 A 2-year-old vegan child with macrocytic anaemia, developmental regression. Most likely deficiency?
Vitamin B12 deficiency. B12 injections or high-dose oral B12. Also check iron, zinc, calcium.
🩸 A 4-year-old with bruising, bleeding gums, petechiae. Deficiency?
Vitamin C deficiency (scurvy). Rare; occurs in severely restricted diets (autism, ARFID).
🦷 A newborn with bleeding from umbilical stump. Deficiency?
Vitamin K deficiency (haemorrhagic disease of the newborn). Prophylaxis at birth.
🍗 What are the 9 essential amino acids?
Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
🐟 Which long-chain polyunsaturated fatty acids are important for brain development?
DHA (docosahexaenoic acid, omega-3) and AA (arachidonic acid, omega-6). Present in breast milk; added to some formulas.
📊 What is the difference between RNI and EAR?
EAR: meets needs of 50% of population. RNI: meets needs of 97.5% (EAR + 2 SD). Used for individual dietary planning.