Iron 101: RDA, Heme vs Non‑Heme, Absorption Boosters & How to Beat Fatigue
Pair lentils with bell‑pepper salsa and skip tea at meals—small tweaks can double your non‑heme iron uptake and keep ferritin levels in the sweet spot.
Hook
**One in three women worldwide is iron‑deficient, yet 70 % of cases could be prevented with simple dietary tweaks.**
TL;DR
- RDA: 18 mg (women 19‑50 y), 8 mg (men & ≥ 51 y)
- Heme iron (meat, fish) absorbs 15‑35 %; non‑heme (plants) 2‑20 %
- Vitamin C ×3 uptake; tea/coffee ↓ 40 %
- Ferritin goal: 30–150 µg L⁻¹
What is iron & why we need it?
Iron forms **haemoglobin** (oxygen transport), **myoglobin** (muscle oxygen) and is a co‑factor for DNA synthesis and immune enzymes.
RDA & upper limit
| Group | RDA | UL |
|-------|-----|----|
| Women 19‑50 y | 18 mg | 45 mg |
| Pregnant | 27 mg | 45 mg |
| Men 19+ y | 8 mg | 45 mg |
| Post‑menopausal | 8 mg | 45 mg |
Top food sources (per portion)
| Food | Iron (mg) | Type |
|------|-----------|------|
| Beef liver 85 g | 5.4 | Heme |
| Canned sardines 90 g | 2.5 | Heme |
| Cooked lentils 1 cup | 6.6 | Non‑heme |
| Firm tofu 100 g | 3.3 | Non‑heme |
| Pumpkin seeds 30 g | 2.7 | Non‑heme |
Absorption boosters & blockers
- **Boosters**: 50 mg vit C (½ bell pepper) with meal ↑ non‑heme x3; heme iron in same meal ↑ non‑heme 1.5× (meat‑factor).
- **Blockers**: phytate (bran), polyphenols (tea/coffee), calcium ≥ 300 mg (dairy) compete.
- **Tip**: Drink tea/coffee ≥ 1 h after meals; sprout/soak beans to cut phytate 30 %.
Deficiency & excess
- **Deficiency**: low ferritin < 15 µg L⁻¹ → fatigue, brittle nails, pica.
- **Excess**: hereditary haemochromatosis or > 45 mg/day supplements → oxidative damage, liver overload.
Practical tips
- Combine plant iron with vit C‑rich veg (e.g. lentil‑tomato stew).
- Cast‑iron skillet cooking adds 1‑2 mg Fe per portion.
- Space calcium & iron supplements by 2 h.
Myth vs fact
| Myth | Fact |
|------|------|
| “Spinach is an iron powerhouse.” | Only 2 mg/100 g + high oxalate ↓ absorption.
| “Vegans can’t meet iron needs.” | Well‑planned vegan diets often hit 18‑20 mg; absorption optimized with vit C.
| “Iron supplements work instantly.” | It takes 4–6 wks to raise ferritin appreciably.
Take‑home message
Hit the RDA with a mix of heme and vitamin C‑paired plant sources, time tea/coffee carefully, and check ferritin yearly—your energy levels will thank you.
References
1. WHO. *Global Anaemia Report* 2024.
2. Hurrell RF. *Am J Clin Nutr* 2023.
3. NIH ODS Iron Fact Sheet, 2024.