Supplements
vitamin C increases non-heme iron absorption
In plain terms: Does vitamin C help you absorb iron?
Part of: 🧪 vitamin C
Yes—it chemically boosts absorption of non-heme (plant/supplement) iron, the basis for 'take iron with orange juice.'
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: Human trials (RCT / n-of-1)
How the studies fall
What the evidence shows
Mechanistically solid: ascorbate reduces ferric to ferrous iron, and controlled human absorption studies show it substantially raises **acute** non-heme iron uptake (e.g. Fe-ascorbate ~44% vs ~1% for a poorly-absorbed ferric complex). This is the reduction chemistry behind 'take iron with orange juice.' **But** see [[claim-vitamin-c-improves-iron-deficiency-treatment]] — this acute enhancement doe
The evidence (4)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Teucher et al. 2004 · Int J Vitam Nutr Res | observational | supports | moderate | Review of enhancers: ascorbic acid is the most efficient enhancer of non-heme iron absorption (Fe3+->Fe2+ reduction), strongest against inhibitor-rich meals (~2:1 molar ratio). |
| Lonnerdal 2007 | observational | mixed | low | Human + Caco-2: ascorbic acid had LIMITED effect on ferritin-BOUND iron (absorbed via a distinct receptor-mediated route) — AA enhancement applies to ionic non-heme iron, not intact ferritin. |
| Kaltwasser et al. 1987 | observational | supports | moderate | Human absorption study: Fe(II)-ascorbate whole-body retention 43.7% vs 1.2% for Fe(III)-hydroxide-polymaltose complex — ascorbate markedly increases iron bioavailability. |
| Olivares et al. 2016 · Biol Trace Elem Res | RCT | supports | moderate | Controlled human radioisotope study (n=14): ascorbic acid enhanced non-heme Fe absorption (57-64% vs 38.8% for Fe alone), confirming the enhancing effect (paper's twist: Cu at 8:1 blunts it). |
Disagree, or know a study we missed?
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Educational only, not medical advice. Grades and scores reflect published evidence weighted by study design and quality; see the methodology.