Normal nutritional requirements across childhood: SAQ

This boy is a healthy, normally growing seven-month-old at the point of transition from exclusive breastfeeding to complementary feeding. His weight tracking along the 25th centile confirms that his requirements have been met to date. The clinical task is to advise his mother on micronutrient supplementation, the timing of cow's milk, the prioritisation of iron-rich foods, and how his requirements will change as he grows. [4]

Question 1 (10 marks)

Outline your advice to this mother on complementary feeding and micronutrient supplementation, including the foods to prioritise, the supplements he needs, and the timing for introducing cow's milk. [4]

Complementary feeding is appropriate because he is seven months old, within the window of not before four months and not after six months recommended by the European Society for Paediatric Gastroenterology, Hepatology and Nutrition. The foods should be iron-rich because the iron store laid down at birth is depleted by around six months. Red meat, iron-fortified cereal, legumes and leafy vegetables should be offered alongside continued breastfeeding, with textures progressing from smooth puree to mashed and then to family textures by around one year. [4]

The 2017 ESPGHAN position paper established that there is no evidence that delaying allergenic foods such as egg or peanut prevents allergy, and these should be introduced alongside other solids rather than avoided. This is an important point to make to the mother, as outdated advice to delay allergens is still common. [5]

Two micronutrient supplements are needed. Vitamin D at 400 international units per day is recommended for all infants from the first days of life and should continue, because breast milk does not reliably provide enough. Iron supplementation at 1 milligram per kilogram per day of elemental iron is recommended for exclusively breastfed term infants from about four months, and this boy should have been started on it a month ago if he was not. [6]

Cow's milk should not be introduced as a main drink before twelve months. Before that age it causes occult gastrointestinal blood loss, imposes a high renal solute load, and displaces iron-rich foods. Small amounts in cooked foods are acceptable, but cow's milk as the main drink waits until one year, and intake should then be capped at about 500 millilitres per day to protect iron status. [10]

Question 2 (10 marks)

Describe how this child's energy and protein requirements will change as he grows from infancy through adolescence, and explain the physiological reason for the pattern. [1]

Energy and protein requirements are highest per kilogram in early infancy, when growth is fastest. Infants require about 80 to 120 kilocalories per kilogram per day and about 1.5 grams per kilogram per day of protein, which reflects both the cost of maintaining a metabolically active body and the cost of depositing new tissue. [1]

As he grows, the per-kilogram requirement falls steadily. By school age the energy requirement is about 60 kilocalories per kilogram per day and by late adolescence about 40 to 55 kilocalories per kilogram per day, with protein falling to about 0.85 grams per kilogram per day. The absolute daily intake, however, rises throughout childhood because his body mass increases so substantially. [1]

The physiological reason is that total energy intake partitions into basal metabolism, physical activity, the thermic effect of food, faecal and urinary losses, and the energy deposited as new tissue during growth. The growth component is large in infancy, when up to a third of intake is deposited as new tissue, and shrinks toward the adult value of near zero as growth velocity slows. This falling cost of growth is what lowers the per-kilogram requirement with age. [1]

Basal metabolism remains the largest single component throughout childhood, taking about 50 to 60 percent of total energy. The brain dominates basal metabolism in infancy because it is such a large fraction of body mass, which is why undernutrition in this period is so damaging to neurodevelopment. The practical message for this mother is that his requirement per kilogram will fall but his total food intake will rise, and the focus will shift from the composition of individual feeds to the overall dietary pattern and physical activity. [1]