Normal nutritional requirements across childhood: Case

This girl presents the picture of an adolescent whose dietary change has left her short of several requirements at once. Her fatigue, pallor, microcytic anaemia with a haemoglobin of 92 grams per litre, and ferritin of 6 micrograms per litre establish iron deficiency anaemia. Her weight falling from the 40th to the 15th centile while her height holds on the 50th shows that her energy and protein intake are also failing to meet her requirements. The strict vegan diet begun nine months ago, combined with the onset of menstruation, explains both gaps. ^[7]

Clinical findings

The clinical picture is one of nutritional inadequacy in an adolescent at a high-requirement life stage. The weight falling from the 40th to the 15th centile over a year is downward centile crossing, the single most reliable sign of failing to meet requirements. Her height remaining on the 50th centile shows that the deficit is recent enough to have affected weight before length, consistent with the timeline of her dietary change. ^[1]

The iron deficiency is driven by two converging factors. Her vegan diet removes the most bioavailable source of iron, which is haem iron from meat, and her recently commenced menstruation adds an ongoing iron loss. The recommended dietary allowance for iron in adolescent females is 15 milligrams per day, the highest of any age group in childhood, precisely because menstruation compounds the baseline requirement. Her diet is providing far less than this. ^[7]

Her body mass index on the 12th centile confirms that her energy intake is below her requirement. Adolescence is a period of increased energy and protein need because of the pubertal growth spurt, and a poorly planned vegan diet that is low in energy-dense foods can fall short. The candidate must assess the whole requirement, not only the iron that the blood test revealed. ^[2]