How does taking vitamin C with ferrous sulfate (iron supplement) affect iron absorption?

Vitamin C Significantly Enhances Iron Absorption from Ferrous Sulfate

Taking vitamin C with ferrous sulfate significantly enhances iron absorption by forming a chelate with iron that prevents formation of insoluble iron compounds and by reducing ferric iron to the more absorbable ferrous form. 1, 2

Mechanism of Action

Vitamin C improves iron absorption through several mechanisms:

• Forms a chelate with iron that prevents formation of insoluble iron compounds
• Reduces ferric (Fe³⁺) iron to ferrous (Fe²⁺) iron, which is more readily absorbed
• Allows iron absorption even when calcium or fiber is present in meals
• Particularly beneficial for non-heme iron (found in plant foods), which has lower bioavailability (1-15%) compared to heme iron (15-40%) 1

Recommended Approach

Optimal Dosing

• Recommended vitamin C dose: 500 mg when taken with ferrous sulfate 1, 2
• Take iron on an empty stomach when possible for best absorption
• If GI side effects occur, iron can be taken with food, but add vitamin C to counteract the reduced absorption 2
• Take iron only once daily rather than in divided doses, as multiple daily doses increase hepcidin levels and reduce absorption from subsequent doses 3
• Consider alternate-day dosing which may improve both tolerance and absorption 1, 3

Timing Considerations

• Avoid taking iron with tea or coffee, as these are powerful inhibitors of iron absorption
• Wait at least one hour after consuming tea or coffee before taking iron supplements 1
• If taking with food, combining with meat protein can further improve absorption 1

Clinical Benefits

• Vitamin C supplementation is a practical approach to lower the risk of iron deficiency and minimize iron-deficiency anemia 1
• Particularly beneficial for those consuming primarily plant-based diets, where non-heme iron predominates 1
• Helps overcome the inhibitory effects of phytates, polyphenols, and calcium on iron absorption 2, 4

Cautions and Contraindications

• Avoid vitamin C supplementation in patients with hemochromatosis or iron overload conditions, as it may accelerate iron deposition in tissues 1, 5
• If vitamin C must be used in patients with iron overload, limit to 500 mg daily 1
• In patients with thalassemia major, high-dose vitamin C has been associated with acute deterioration of cardiac function 1

Common Side Effects of Ferrous Sulfate

• Constipation (12% of patients)
• Diarrhea (8% of patients)
• Nausea (11% of patients) 1

Practical Implementation

1. First-line approach: Ferrous sulfate with 500 mg vitamin C taken once daily on an empty stomach
2. If GI side effects occur: Take with small amounts of food plus vitamin C
3. If poor response: Consider alternate-day dosing with vitamin C
4. Monitor response: Hemoglobin should increase by 1 g/dL within 2 weeks of supplementation 1
5. If no improvement: Consider IV iron if oral iron with vitamin C fails after 1 month of adherent use 1

By following these evidence-based recommendations, vitamin C can significantly enhance iron absorption from ferrous sulfate supplements, improving outcomes in patients with iron deficiency anemia while minimizing side effects.