The Curious Case of the Nail in the Onion: A Forgotten Folk Remedy, Rediscovered
- Rust (iron oxide) slowly leaches into the acidic environment of the cooking onion.
- The onion’s natural acids (like ascorbic acid) help convert this iron into a more bioavailable form—non-heme iron, which the body can absorb more readily when paired with vitamin C (which onions contain!).
Traditional use:
A single onion with a nail, cooked in broth for 30+ minutes, can increase iron content by 2–5 mg—meaningful for those with marginal intake. It was never a cure, but a gentle, food-based support—especially for postpartum women or growing children.
NOTE: MODERN STUDIES (LIKE A 2012 LANCET TRIAL IN CAMBODIA) CONFIRM IRON INGOTS IN POTS SIGNIFICANTLY REDUCE ANEMIA. THE NAIL-IN-ONION IS THE HOME-KITCHEN COUSIN OF THIS PRACTICE.
2. A Gardener’s Secret for Stronger Plants
Leftover onion scraps? Stick a nail in them before composting or burying. Why?
- Iron is essential for chlorophyll synthesis—the green pigment in plants.
- In iron-poor soils, this slow-release method helps prevent chlorosis (yellowing leaves) in tomatoes, peppers, and roses.
- The onion acts as a carrier, delivering iron directly to the root zone as it decomposes.
