Plant-Based Endurance Athlete with Low Ferritin
Dev, 29, trains for half-marathons (55–70 km/week) and has followed a vegan diet for two years. He complains of heavy legs, breathlessness on easy runs, and a resting heart rate up 8 bpm. Labs: ferritin 18 ng/mL (reference 30–300), hemoglobin 132 g/L, MCV 78 fL, B12 180 pmol/L (reference 200–900), CRP 8 mg/L, and no celiac screening. He takes a multivitamin with 10 mg iron, drinks black tea with every meal, and eats 60–70 g protein/day at 72 kg. He is 178 cm tall and has lost 2 kg unintentionally since increasing mileage. He has no GI symptoms but occasionally takes omeprazole for heartburn. He wants to know whether to take a 65-mg iron tablet twice daily, start B12 injections, and add an 'iron absorption booster.'
1. Interpret Dev's labs and symptoms. What is your working hypothesis, and what additional information or referrals are needed before recommending iron?
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The picture suggests iron deficiency with possible early microcytic change plus low B12, but it is not a simple 'take iron' case. Ferritin 18 ng/mL is low, MCV 78 fL is microcytic, and hemoglobin 132 g/L is low-normal for a male endurance athlete. However, CRP 8 mg/L is elevated, and ferritin is an acute-phase reactant-inflammation can falsely raise it, so his true iron status may be worse. B12 at 180 pmol/L is below reference and could contribute to fatigue and neurological symptoms.
Before recommending iron, I would want repeat CBC, transferrin saturation, TIBC, and possibly methylmalonic acid or homocysteine. Celiac screening (tTG-IgA with total IgA) is important in a vegan with iron and B12 deficiency. I would ask about bleeding, heavy training loads, GI symptoms, and omeprazole use, which reduces iron absorption. I would refer to his GP for iron studies and B12 evaluation. High-dose iron and B12 injections are medical decisions, not coaching prescriptions.
2. Describe the dietary and supplement education you would provide to improve iron and B12 status while respecting his vegan diet.
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I would focus on absorption and adequacy, not just total iron. Non-heme iron from lentils, tofu, tempeh, fortified cereals, pumpkin seeds, and dark leafy greens should be paired with vitamin C (citrus, pepper, tomato) at meals. Tea and coffee should be moved at least one hour away from iron-containing meals because polyphenols inhibit absorption. Cast-iron cookware can add small amounts. His protein intake of 60–70 g/day at 72 kg is about 0.9 g/kg-low for endurance training; I would discuss 1.4–1.8 g/kg, distributed across meals, using tofu, tempeh, seitan, legumes, and plant protein blends.
For B12, fortified foods are helpful but dose is uncertain; a cyanocobalamin supplement of 25–100 mcg daily or 1,000 mcg two to three times weekly is common, but I would have his GP confirm the regimen. I would not rely on a multivitamin with 10 mg iron to correct deficiency, and I would not recommend a proprietary 'absorption booster' without evidence.
3. He asks you to prescribe 65 mg elemental iron twice daily and to arrange B12 injections so he can avoid a GP visit. How do you respond?
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I would explain that prescribing iron and arranging injections are outside my scope. A 65-mg elemental iron tablet twice daily is 130 mg/day, which can cause constipation, nausea, and dark stools, and in the wrong situation can mask GI bleeding or contribute to iron overload. Absorption is also affected by omeprazole, tea, and timing. B12 injections require a diagnosis and a medical plan; oral high-dose B12 may be appropriate for some people, but that is a clinical decision.
I would offer to help him prepare for the GP visit: symptom log, training load, diet recall, supplement list, and questions about iron studies, celiac screening, and B12. I can coach meal timing and iron pairing, and I can monitor adherence and side effects once a clinician has set the plan. If he refuses medical care, I would document that I advised evaluation and did not prescribe.