Iron and Vitamin C in a Plant-Based Teenager
A 16-year-old girl follows a strict vegan diet and presents with fatigue. Labs show hemoglobin 10.2 g/dL, ferritin 8 ng/mL, and mean corpuscular volume 74 fL, consistent with iron-deficiency anemia. She drinks tea with most meals and takes a calcium supplement at breakfast. She eats lentils, spinach, and fortified cereal but rarely combines them with vitamin C sources. Her family asks whether she should just take an iron pill or change her diet, and whether the tea and calcium matter. She also has a heavy menstrual period each month.
1. Explain the physiological and dietary factors contributing to her iron deficiency, and evaluate the roles of tea, calcium, and vitamin C.
Read the worked answer
Several factors converge:
- Low bioavailability of non-heme iron. Plant foods contain non-heme iron, which is absorbed less efficiently than heme iron. Her diet relies entirely on non-heme sources (lentils, spinach, fortified cereal).
- Inhibitors at meals. Tannins in tea bind iron and reduce absorption, especially when tea is drunk with meals - she does this at most meals. Calcium also inhibits iron absorption, and her breakfast calcium supplement competes with the fortified cereal. Both are modifiable timing issues.
- Absence of enhancers. Vitamin C converts ferric to ferrous iron and forms a soluble chelate, markedly improving non-heme absorption. She rarely pairs iron foods with vitamin C sources, so she loses this benefit.
- Ongoing losses. Heavy menstrual bleeding increases iron requirements and can exceed absorption even with a good diet, explaining why deficiency developed despite intake.
The conclusion: this is a combination of increased losses (menses), low-bioavailability intake, inhibitor timing, and missing enhancers - not simply "not enough iron in the diet."
2. Recommend a management plan that addresses both diet and supplementation, and explain the reasoning behind the timing advice.
Read the worked answer
Management should combine supplementation and dietary change:
Supplementation: Oral iron (e.g., ferrous sulfate) is appropriate for moderate iron-deficiency anemia, taken on an empty stomach if tolerated. Taking it with a vitamin C source (e.g., orange juice) improves absorption. Alternate-day dosing may be considered because daily dosing can increase hepcidin and reduce fractional absorption; this should be individualized with the clinician. Recheck hemoglobin and ferritin after an appropriate interval.
Dietary changes:
- Pair non-heme iron foods (lentils, spinach, fortified cereal) with vitamin C sources (citrus, peppers, tomatoes) at the same meal.
- Move tea away from meals - drink it between meals, not with iron-containing food.
- Move the calcium supplement away from iron-containing meals (e.g., bedtime), since calcium and iron compete.
- Include other iron-rich foods and consider fortified options.
Address losses: Evaluate and manage heavy menstrual bleeding with the appropriate clinician, since ongoing loss can defeat dietary and supplement efforts.
Monitoring: Repeat labs to confirm response; if there is no response, evaluate for malabsorption or continued blood loss. Emphasize that diet alone may be insufficient while losses are heavy, so supplementation plus timing changes plus gynecologic evaluation is the coordinated plan.