Vitamin C for Iron Absorption
100 mg vitamin C with an iron-containing meal can double or triple non-haem iron uptake.
Overview
Verdict
Mechanistically well established and consistently reproduced in meal-absorption studies; whole-diet and longer-term iron status effects are more modest.
How It Works
Key mechanistic steps
Dosing & Protocol
Practical pairing amounts
| Setting | Vitamin C | Timing | Notes |
|---|---|---|---|
| Plant-based meal | 50-100 mg | With the meal | Roughly one orange, half a bell pepper or 120 mL orange juice |
| Iron tablet | 100-250 mg | Same time as the tablet | Ascorbic acid is often already included in iron formulas |
| Meal with tea or coffee | 100 mg or more | With the meal | Better still, move the drink 1-2 hours away from the meal |
| Overweight or obesity | 100-250 mg | With the meal | Enhancement is about half as large; do not assume a fixed multiplier |
Ascorbic acid must be present in the same meal. Taken hours apart it does nothing for that meal.
Vitamin C does not replace iron
If ferritin is low, the limiting factor is iron intake, not absorption efficiency. Vitamin C makes an adequate iron dose work harder; it cannot make an inadequate one sufficient.
Evidence
Studies linked to this pairing.
Effect of ascorbic acid intake on nonheme-iron absorption from a complete diet
Cook JD, Reddy MB
There was no significant difference in mean iron absorption among the 3 dietary periods despite a range of mean daily intakes of dietary vitamin C of 51-247 mg/d.
In overweight and obese women, dietary iron absorption is reduced and the enhancement of iron absorption by ascorbic acid is one-half that in normal-weight women
Cepeda-Lopez AC, Melse-Boonstra A, Zimmermann MB +1 more
Geometric mean iron absorptions were 29.5% in normal-weight and 16.6% in overweight and obese women from meals with ascorbic acid.
Safety
Do not force absorption with iron overload
In haemochromatosis or transfusional iron overload, high-dose vitamin C can mobilise iron and worsen tissue loading. Pair only under medical supervision.
Interactions & Conflicts
Interactions and competing factors
| Interacts with | Severity | Mechanism | Action |
|---|---|---|---|
| Calcium supplements or dairy | moderate | Calcium inhibits non-heme iron absorption and blunts the ascorbic acid effect | Separate calcium from the iron-containing meal by at least two hours |
| Tea, coffee, red wine | moderate | Polyphenols chelate iron into unabsorbable complexes | Move drinks 1-2 hours from the meal; extra vitamin C only partly compensates |
| Proton pump inhibitors | moderate | Reduced gastric acid lowers iron solubility before ascorbate acts | Expect a smaller gain; discuss iron status monitoring |
| Levothyroxine, tetracyclines, quinolones | moderate | Iron binds these drugs and reduces their absorption | Keep the iron dose at least four hours from these medicines |
| Haemochromatosis or iron overload | high | Enhanced absorption and iron mobilisation add to tissue loading | Avoid deliberate pairing; specialist supervision required |
References
Medical Disclaimer
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