A balanced diet must include a variety of nutrients. Describe the roles of iron and vitamin D in the body, and explain what happens if each of these nutrients is absent from the diet.

Cambridge International IGCSE Biology (0610) — 7.1 Diet · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Iron is required for the production of haemoglobin in red blood cells, which carries oxygen to tissues. A deficiency of iron causes iron‑deficiency anaemia, characterised by tiredness and reduced oxygen delivery.

Vitamin D is essential for the intestinal absorption of calcium and for maintaining healthy bones and teeth. Without sufficient vitamin D, calcium uptake is impaired, leading to rickets in children and osteomalacia in adults, characterised by weak or soft bones and bone deformities.

Examiner tips

  • Use the exact terms "haemoglobin", "iron‑deficiency anaemia", "rickets", "osteomalacia"; link each nutrient to its specific role and the disease that results from deficiency.
  • Show the causal chain: nutrient → function → deficiency disease.
  • Keep the answer concise – 4 marks allow two short sentences per nutrient.

Common mistakes

  • Confusing iron with other minerals (e.g. zinc) or omitting haemoglobin; describing only tiredness without mentioning anaemia; using "vitamin D deficiency causes osteoporosis" instead of rickets/osteomalacia; failing to mention calcium absorption for vitamin D.

Mark scheme (4 marks)

  1. Iron is needed for the production of haemoglobin (in red blood cells).
  2. A lack of iron leads to anaemia, causing tiredness (because insufficient oxygen is transported / insufficient energy is produced).
  3. Vitamin D helps the uptake / absorption of calcium during digestion and is needed to maintain healthy bones (and teeth).
  4. A lack of vitamin D causes rickets, leading to weak / soft bones or bone deformities (or stunted growth in children).

Key terms in this question

iron · vitamin D

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