How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Iron
The oxygen transport mineral. Its deficiency is the most widespread in the world, but excess is toxic: this is the supplement you do not take blindly.
Benefits
- Delays fatigue in non-anemic but deficient women: clear effect as early as one month, versus placebo
- Improves attention and concentration, including in non-anemic individuals (meta-analysis in children and adults)
- Prevents anemia and deficiency during pregnancy (review involving 43,274 women)
- In the deficient child, catches up on motor and language development delays
Precautions
Do not supplement without blood testing: the body has no way of eliminating an excess of iron, which accumulates in the liver. Digestive disorders and very black stools are very frequent. Take away from tea, coffee, and calcium, which reduce absorption. Also good to know: in a pregnant woman who is neither anemic nor deficient, systematic supplementation provides no proven benefit, and a hemoglobin level that is too high is associated with the same risks as a level that is too low.
Recommended dosage
30 to 100 mg of iron per day in trials in adults, after testing: the benefits are seen in deficient or anemic individuals.
How to take it
- First a blood test: benefits are seen in deficient or anemic individuals. In children without deficiency, iron even slowed down weight gain or growth.
- Trial doses in adults: 30 to 100 mg of iron per day, for example 80 mg of ferrous sulfate against fatigue.
- Fatigue without anemia: in non-anemic women, 80 mg per day reduced fatigue in one month, especially when ferritin was low (50 µg/l or less).
- How long: 8 weeks of ferrous sulfate were enough to correct the iron status of deficient adolescent girls.
- During pregnancy: daily intake reduces anemia and deficiency, but too much iron could also be harmful: the risk for the baby follows a U-shaped curve depending on the mother's hemoglobin.
- If your gut cannot handle it: in one trial, intravenous iron was better tolerated than oral iron. This is a medical decision.
What the studies say
This systematic review and meta-analysis examined the efficacy and safety of daily oral iron supplementation in children aged 4 to 23 months. Iron supplementation effectively reduces the risk of anaemia and iron deficiency. However, the effects on mental and psychomotor development, growth and the adverse effect profile (vomiting, more frequent fever) remain uncertain and require more robust studies.
Pasricha SR, Hayes E, Kalumba K, Biggs BA. — The Lancet. Global health (2013) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more