A Student's Diet and Iron Absorption
A 15-year-old student, Kenan, feels tired during afternoon PE lessons. He eats cereal with milk for breakfast, a white-bread sandwich with cheese at school, and pasta with tomato sauce for dinner. He drinks tea with most meals and rarely eats meat, beans, or green leafy vegetables. His doctor suspects low iron intake. The biology teacher explains that iron from plant foods is absorbed less efficiently than iron from meat, and that vitamin C improves absorption while tea can reduce it. Kenan wants to change his meals without buying expensive supplements.
1. Explain, using the biology of digestion and absorption, why Kenan's diet may lead to low iron even if he eats enough total food.
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Why total food is not enough: Iron exists in two forms. Haem iron from meat, fish and poultry is absorbed relatively easily. Non-haem iron from plants, cereals and dairy is absorbed poorly because it is bound to compounds (such as phytates in cereals) that the body cannot easily release.
Kenan's diet: His meals are dominated by cereal, bread, pasta and dairy - sources of non-haem iron at best, and dairy contains almost no iron. He rarely eats meat, beans or leafy greens, so both his total iron and the easily absorbed share are low.
Absorption site: Iron is absorbed mainly in the small intestine. If inhibitors are present in the same meal, less iron crosses the intestinal wall into the blood, so even a diet with some iron can leave the body short. Low iron reduces haemoglobin, which carries oxygen, explaining his tiredness in PE.
2. Propose three specific, low-cost changes to Kenan's meals and explain the mechanism by which each should help.
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1. Add a vitamin C source to meals (e.g. a glass of orange juice, a tomato, or peppers with the pasta). Vitamin C keeps iron in a more absorbable form and counters inhibitors, so more non-haem iron crosses the small intestine.
2. Move tea away from meals (drink it between meals instead). Tea contains tannins/polyphenols that bind iron and reduce absorption; separating tea from food removes this inhibition.
3. Add cheap plant iron sources such as beans, lentils or dark leafy vegetables, and combine them with the vitamin C source. Beans and lentils are inexpensive and provide non-haem iron in larger amounts than white bread.
Reasoning: Each change works on a different lever - more iron in the meal, better release of that iron, and fewer inhibitors. Together they raise absorbed iron without supplements, which fits Kenan's budget.
3. Kenan says he will simply drink more milk because "milk is healthy". Evaluate this plan.
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Evaluation: Milk is valuable for calcium and protein, but it is a poor source of iron and can make the iron problem worse if it replaces iron-rich foods. If Kenan drinks more milk instead of eating beans, lentils or meat, his iron intake falls further.
Also: Calcium can compete with iron absorption when consumed in large amounts at the same meal, so loading up on milk at mealtimes is not a good strategy for someone with suspected low iron.
Conclusion: The plan is not sound for this specific problem. Milk should be kept as part of a balanced diet, but the priority is adding iron-rich foods and vitamin C and reducing tea at meals. "Healthy" is not a property of a single food - it depends on what the food replaces and what the body needs.