Does Cooking on Cast Iron Increase Iron Intake?
Yes, cooking on cast iron cookware does increase the iron content of food, and when combined with dietary strategies to enhance absorption (particularly vitamin C), it can serve as a practical adjunct intervention to improve iron status, especially in children.
Evidence for Iron Leaching from Cast Iron Cookware
Cast iron cookware does leach iron into food during cooking, increasing the iron content of prepared meals 1, 2, 3. However, the clinical effectiveness of this approach shows mixed results depending on the population studied and compliance with cookware use 1, 3, 4.
Effectiveness in Different Populations
Children show the most consistent benefit:
- 50% of studies in children (ages 4 months-11 years) demonstrated statistically significant increases in hemoglobin levels (ranging from -0.4 to 1.20 g/dL improvement) when cast iron pots were used regularly 4
- A systematic review found that four studies reported significant increases in blood hemoglobin levels with iron cookware use 1
Females of reproductive age show less consistent results:
- Only 28.6% of studies in females of reproductive age (12-51 years) showed significant improvements in iron status 4
- One high-quality randomized trial in young women with mild iron deficiency found that increased use of cast-iron cookware as part of a comprehensive dietary intervention led to a 26% increase in serum ferritin, though this did not reach statistical significance (p=0.068) 2
Critical Limitation: Bioavailability Concerns
A major caveat is that iron leached from cookware may not be highly bioavailable:
- One randomized clinical trial in Benin found no evidence that iron cooking pots were effective against iron deficiency anemia, with the control group (receiving iron supplements) showing significantly higher serum ferritin concentrations (p<0.0001) compared to those using iron pots 5
- This study raised important questions about whether the iron leached from pots is actually bioavailable for absorption 5
Maximizing Effectiveness: The Vitamin C Strategy
To optimize any potential benefit from cast iron cookware, you must combine it with vitamin C-rich foods at the same meal:
- Vitamin C is the most potent enhancer of non-heme iron absorption, which is the type of iron that leaches from cookware 6, 7
- A minimum of 80 mg of vitamin C should accompany iron-containing meals 6, 7
- Vitamin C-rich foods include citrus fruits, potatoes, vegetables, and salads 7
Foods to Avoid at Iron-Rich Meals
Critical inhibitors that will negate the benefit of cast iron cookware:
- Tea should be consumed between meals, not with meals, as tannins powerfully inhibit iron absorption 6, 7
- Calcium from dairy products inhibits iron absorption—avoid milk, yogurt, or cheese with iron-rich meals 6, 7
- Phytates in bran and whole grains decrease bioavailability 8, 7
Compliance and Practical Considerations
Compliance with cast iron cookware use varies considerably:
- Daily use of pots ranged from only 26.7-71.4% in studies, while iron ingots showed better compliance at 90-93.9% daily use 4
- Compliance depends on pot size, whether it replaces or supplements existing cookware, and cultural familiarity with cast iron 3
Clinical Recommendation Algorithm
For populations at risk of iron deficiency:
Primary strategy: Prioritize dietary iron from meat, poultry, and fish (15-40% absorption) over plant-based sources (1-15% absorption) 7
Adjunct strategy: Use cast iron cookware as a complementary intervention, particularly for children, but never as the sole intervention 4
Essential co-intervention: Always pair meals cooked in cast iron with vitamin C-rich foods (minimum 80 mg) 6, 7
Avoid inhibitors: Consume tea, coffee, and dairy products at least 1-2 hours away from iron-rich meals 6, 7
Monitor effectiveness: If using cast iron cookware as part of an iron-boosting strategy, monitor hemoglobin and ferritin levels to ensure adequacy, as the bioavailability of leached iron remains uncertain 5
Bottom Line
Cast iron cookware can increase food iron content and may improve iron status in children when used consistently and combined with vitamin C-rich foods 1, 2, 4. However, it should be viewed as a cost-effective complementary strategy rather than a standalone solution, given the mixed evidence on bioavailability and the superior effectiveness of dietary heme iron sources and iron supplementation when clinically indicated 5, 4.