Iron
What the European Food Safety Authority and the United States National Institutes of Health have published about iron intake, and what the catalogue records. Reference figures and citations only.
Stacky is an organisational tool, not a medical device. It does not provide medical advice, and nothing on this page says what iron does. Talk to a doctor or pharmacist before starting, stopping or changing what you take.
Published intake references
Each figure is one authority’s published value, with the kind of figure and the people it applies to as that authority stated them. Where the EU and the US differ, both are shown and neither is averaged or converted. Only a tolerable upper intake level sets a ceiling. A recommended or adequate intake is context, not a limit.
EUEuropean Union — EFSA
USUnited States — NIH ODS / IOM
“None established” means that authority examined iron and set no upper limit. What it published instead is below, with its own label.
Also published, and not a limit
These are the authority’s own words for a figure that is not a tolerable upper intake level. The app never compares a dose against one; this page prints it because the authority did.
To cite a figure, cite the authority’s document linked on its card, and this page as where you read it: stacky-app.com/substances/iron, retrieved 13 November 2026. Every card has its own address: add #eu-rda-2 to the page URL for the first one.
Forms of iron with their own page
The figures above are set on iron, the element. A supplement label may declare the element or the whole salt, and the element is a different fraction of each salt’s weight. Each form’s page shows that fraction and reads the label conventions.
Products in Stacky’s catalogue containing Iron
3 products whose label declares iron, listed by brand and drawn as the app draws them. Amounts are the manufacturer’s printed figures; Stacky has measured nothing and ranks nothing.
How it is recorded
What the app records so it can schedule a dose. None of it is advice.
Default time of day in the app: Morning. A person can move it; the app never changes a dose.
Default food note in the app: on an empty stomach.
Recorded interactions
How Stacky summarises what a named source says about iron taken alongside another substance: absorption and nutrient status only. The category and the summary are Stacky’s words; each row links to the source, and the source’s own wording governs. A row without one is not published, and neither is one whose source description names a disease or clinical condition: 5 such rows for Iron stay in the app. None of these says whether a combination is good or bad.
| Stacky’s category | Summary, in Stacky’s words | Source |
|---|---|---|
| Documented relationship with Calcium | Calcium can reduce the bioavailability of both heme and non-heme iron when the two are taken together. NIH ODS notes the effect has not been definitively established, and that calcium supplementation over several weeks has not been shown to change iron status. Scope the source gave: calcium and iron taken at the same time; applies to both heme and non-heme iron. |
NIH ODS Checked 6 Aug 2026 |
| Documented relationship with Green Tea Extract | Flavonoids from tea bind non-heme iron and inhibit its intestinal absorption, and can also inhibit heme iron absorption. Vitamin C greatly enhances iron absorption and can counteract this effect of flavonoids. Scope the source gave: tea flavonoids consumed with a meal or with iron; one cup of tea with a meal decreased non-heme iron absorption from that meal by about 70%. |
Linus Pauling Institute Checked 6 Aug 2026 |
| Increases absorption or status of Vitamin B3 | Iron is one of the nutrients the tryptophan-to-niacin pathway depends on. People with low iron intakes convert less tryptophan to niacin. | NIH ODS Checked 6 Aug 2026 |
| Documented relationship with Vitamin C | Vitamin C improves the absorption of non-heme iron, the form found in plant foods and most iron supplements. The effect is described for vitamin C and iron consumed together. Scope the source gave: non-heme iron, when the two are consumed in the same meal. |
NIH ODS Checked 6 Aug 2026 |
| Reduces absorption or status of Zinc | Supplements containing 25 mg or more of elemental iron taken at the same time as zinc can reduce zinc absorption and plasma zinc concentrations. Iron used to fortify foods does not significantly interfere with zinc absorption. Scope the source gave: supplements containing 25 mg elemental iron or more, taken at the same time as zinc; iron added to fortified foods does not have this effect. |
NIH ODS Checked 6 Aug 2026 |
Indexed studies
A study reaches this page only if its own title names Iron or one of its recorded alternative names, and does not name a disease or clinical condition. The second rule removes papers that are about iron; a title naming a condition beside a substance reads as a claim, and this page makes none. Titles are the studies’ own words, newest first. A study being listed is not a statement that iron does what it set out to test. How this list is built →
| Title | Journal | Year | Reference |
|---|---|---|---|
| Daily oral iron supplementation during pregnancy. | Cochrane Database Syst Rev | 2024 | PubMed 39145520 |
| The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials. | Nutr Rev | 2023 | PubMed 36728680 |
Showing 2 of the 5 papers indexed against iron in Stacky.
About this page
Stacky is a supplement tracking app. It renders what you take and what published sources say about it; it does not tell you what to take. Every figure on this page names the authority that published it and links to that authority’s own page.
Not on this page: a dose of our own, a grade, a verdict on whether iron works, or any statement that it treats, prevents or improves a condition. How these pages are built →
Figures are read from the authorities’ published tables and can go out of date when those tables are revised. If one here is wrong, tell us at support@stacky-app.com and we will check it against the source.