FMFerric maltolIron held in the ferric state by three maltol ligands, a sugar-derived complex rather than a salt or an amino acid chelate.Trade-off against an intravenous iron it did not meet its non-inferiority margin at week 12, and treatment-emergent adverse events were more frequent (59 against 36 per cent), leading to discontinuation in 10 against 3 per cent
CICarbonyl ironIn female blood donors, 52 percent were still iron deficient at twelve weeks on carbonyl iron, against 80 percent on placebo.Fits Formulations that need a large amount of elemental iron in a small pill, since almost the whole ingredient weight is iron. Its insolubility and low reactivity make it a quiet neighbour in multivitamin blends where soluble ferrous salts can act on other actives, and the gradual dissolution profile is the delivery mechanism the form is chosen for. Well established in over-the-counter iron products with mature pharmacopoeial and supply support.Trade-off At an equal elemental dose the amount of iron reaching body stores is around 70 percent of that from ferrous sulfate. In the donor trial, gastrointestinal complaints were significantly more frequent than with placebo, and about half the treated donors were still iron-deficient at week 12, so an 8-week 45 mg course narrows a deficit rather than closing it.
PIPolysaccharide iron complexFerric iron held inside a partially hydrolysed starch matrix rather than paired with a simple anion. The complex disperses in water without behaving as a free ionic salt, carries a high proportion of iron by weight, and has little of the metallic astringency that dissolved ferrous salts bring. Iron is released from the carbohydrate carrier as the complex breaks down in the gut.Fits Liquid drops, elixirs and other paediatric or taste-sensitive formats, where a near-neutral carrier matters and staining or astringency from a dissolved ferrous salt would be a formulation problem. The complex is stable enough to sit in flavoured liquids, and its high iron content per gram keeps capsule and dose volumes small. Widely used in prescription and over-the-counter paediatric iron products, so sourcing and dosing conventions are established.Trade-off In the head-to-head against ferrous sulfate at the same 3 mg/kg elemental dose, haemoglobin rose 1.0 g/dL less and median ferritin 10.2 ng/mL less over 12 weeks, and diarrhoea was reported by 58 percent of this arm against 35 percent. The haemodialysis finding is a post hoc subgroup analysis whose authors describe it as suggestive and call for prospective study.
HIHeme iron polypeptideHaemoglobin did not differ from monthly IV iron in a 40-person kidney-disease trial, though stored iron ran much lower, and reviewers reported it does not appear to add benefit over standard iron.Fits Products aimed at people who tolerate conventional iron salts poorly, and formulas taken with meals or alongside other minerals, where an iron that is not present as a free ion simplifies the food-timing instructions. The low iron load per dose suits three-times-daily regimens and non-animal-free positioning is a constraint to note since the raw material is animal-derived.
FSFerrous succinateThe iron(II) salt of succinic acid, a four-carbon dicarboxylic acid that is itself an ordinary intermediate of the citric acid cycle. A reddish-brown powder, about a third iron by weight, with modest rather than free water solubility. The counter-ion is a small dietary organic acid rather than a mineral acid such as sulfate.Fits Tablets and capsules where a high elemental share per milligram of raw material keeps the finished dosage form small, which matters when iron shares a tablet with folate, B12 and other actives. The limited water solubility also suits sustained-release matrices and coated tablets, where a formulator wants the iron released along the tract rather than dumped at once in the stomach.Trade-off Ferrous salts as a class carry the familiar gastrointestinal complaints and a metallic taste, and this one is no exception. Its modest solubility makes it awkward in liquids and syrups. It is a less widely traded raw material than sulfate or fumarate, so grade documentation varies between suppliers. No human outcome trial is carried on this row.
FAFerrous ascorbateA compound of iron(II) with ascorbic acid, in which ascorbate acts both as the counter-ion and as a reducing partner that holds the iron in its ferrous state instead of letting it oxidise to ferric. Around 14 percent iron by weight, so the printed weight of the compound is far larger than the elemental iron figure beside it. Water-soluble, pale to greyish in colour, and widely traded in India and other Asian markets as syrups, drops and tablets.Fits Liquid formats, drops and syrups, where an unprotected ferrous salt would oxidise in the bottle and darken over shelf life. It also lets a formulator carry vitamin C alongside iron inside one raw material rather than as a second ingredient line, which simplifies a short panel on a small pack.Trade-off The low elemental share makes for a bulky dose, and the ascorbic acid content is fixed by the stoichiometry of the salt, so it cannot be dialled up or down independently of the iron. Ascorbate is heat and light sensitive, which constrains processing and packaging. Ferrous salts as a class carry the usual gastrointestinal complaints and a metallic taste in liquids. No human outcome trial is carried on this row.
IPIron protein succinylateIron(III) bound inside a shell of succinylated casein, a milk protein whose lysine residues have been reacted with succinic anhydride to make the shell strongly acidic in character. Around 5 percent iron by weight. The succinylated protein stays insoluble at the pH of the stomach and dissolves as the pH rises further down the tract, which is the design intent of the material: the iron is not presented as free ions in the stomach.Fits Single-dose liquid vials, sachets and drops aimed at people who find plain ionic ferrous salts hard to take. The protein shell also masks the metallic character of iron, which is why the form is common in flavoured liquids sold across Italy, Spain and Latin America.Trade-off At roughly 5 percent iron by weight this is a large mass of raw material per milligram of iron, which drives dose volume and cost of goods. It is milk-derived, so it closes off vegan positioning and is unsuitable for a milk-allergy line. There is a body of older clinical work on this material, but none is carried on this row, so no outcome is claimed here.
SISucrosomial ironFerric pyrophosphate carried inside a matrix of phospholipids and sucrose esters of fatty acids, produced as a free-flowing powder. The iron is physically enclosed rather than chemically changed, so the underlying salt is still ferric pyrophosphate. The surrounding matrix is what distinguishes the material. It is tasteless, odourless and non-ionic in the pack.Fits Capsules, stick packs, chewables and children's formats where the metallic character of iron is the formulation problem to solve. The neutral taste and the absence of free ionic iron also make it workable alongside sensitive actives such as vitamin C, probiotics and omega oils in the same blend, and it is plant-derived, so it fits vegan positioning.Trade-off It is a proprietary, single-source ingredient, which ties a formula to one supplier for price and continuity. The elemental iron share of the finished powder is low relative to plain salts, so capsule fill runs high. Much of the published work sits with the ingredient owner and none of it is carried on this row, so no outcome is claimed here.
EIElectrolytic ironIron metal deposited from an iron salt solution onto a cathode, then stripped and milled into flaky, dendritic particles of high surface area. Typically 97 percent or more elemental iron, grey, tasteless and magnetic, which is how quality control confirms it is present in a finished flour or cereal.Fits Dry blends, flour and breakfast cereal fortification, and tablet formulas where the material must not react with anything around it during a long shelf life. Its high surface area relative to other metallic iron grades is the reason a formulator picks it over plain reduced iron in a dry matrix.Trade-off Everything about how this material behaves in the body follows from particle size and surface area, and neither number appears on a supplement panel, so two products naming electrolytic iron are not necessarily comparable. Like all metallic iron it depends on stomach acid to dissolve. No human outcome trial is carried on this row.
RIReduced ironIron metal produced by reducing iron oxide with hydrogen or carbon monoxide at high temperature, leaving porous, sponge-like particles. Iron content is typically in the mid to high nineties by percentage, with the balance made up of residual oxide and trace metals from the ore.Fits Long-life dry goods: flour, pasta, breakfast cereals and low-cost tablet blends, where the deciding factors are that the material adds no colour, no taste and no reactivity to a matrix stored for months. It is the cheapest way to put a large elemental iron figure on a panel, which is why it appears so widely in staple food fortification programmes.Trade-off The porous particles vary in size and residual oxide content between suppliers and even between lots, and none of that reaches the label. Like other metallic irons it depends on gastric acid to dissolve at all. No human outcome trial is carried on this row.
FAFerric ammonium citrateA mixed iron(III) ammonium salt of citric acid, traded in a brown grade and a green grade that differ in iron content and ammonia share. Roughly 16 to 18 percent iron by weight in the brown grade. Unlike most ferric compounds it is freely and quickly soluble in water, because citrate keeps the iron in solution as a complex rather than letting it drop out as hydroxide.Fits Clear liquids, fortified beverages, effervescent tablets and any format where the iron has to go fully into solution and stay there at drinking pH. The citrate complex is also less prone to interacting with proteins in a beverage than a simple ferric salt would be.Trade-off It is hygroscopic and light sensitive, so it needs protective packaging, and both grades add a distinct colour and a metallic edge to a clear drink at higher inclusion levels. The ammonium content is a flavour and labelling consideration in its own right. No human outcome trial is carried on this row.
IPIron polymaltose complexA ferric hydroxide core wrapped in a shell of polymaltose, a partly hydrolysed dextrin. The whole particle behaves as one large, water-soluble, non-ionic unit, so no free ferric ion is released in the stomach. Brown in colour, near-neutral in taste, and stable in solution across a wide pH range.Fits Chewable tablets, syrups and drops sold across Europe, Australia and much of Asia, particularly children's and pregnancy formats where taste and staining are the design constraints. The non-ionic character means it does not blacken teeth or react with tannins in tea and coffee the way a ferrous salt does.Trade-off Like other polymer-shelled irons it is defined by its process, so specifications differ between manufacturers. It is a bulky material per milligram of iron, which sets a practical ceiling on the dose that fits in one chewable. No human outcome trial is carried on this row.
SFSodium feredetateIron(III) locked into the six-armed chelate EDTA with sodium as the counter-ion, roughly 13 percent iron by weight. The chelate is unusually stable: it holds the iron across a wide pH range, keeps it out of reach of phytate and polyphenols in a food matrix, and stops it acting as a catalyst for fat oxidation in the pack.Fits Fortification of high-phytate staples such as soy sauce, fish sauce, curry powder and wheat flour, where a plain iron salt would bind up with phytate or turn the product dark. In supplements it appears in liquids and syrups that also carry plant material, since the chelate does not react with the polyphenols around it. EDTA in the same molecule doubles as a stabiliser for the rest of the formula.Trade-off Regulators cap EDTA intake, so the amount of iron that can be delivered this way is limited by the chelator rather than by the iron, and some markets restrict the ingredient to named food categories. Low elemental share makes it bulky. No human outcome trial is carried on this row.Active and formulation aid
FOFerric orthophosphateIron(III) phosphate, FePO4, an off-white to buff powder that is practically insoluble in water, with roughly 29 percent iron by weight in the hydrated grade sold for foods. Being insoluble and near-colourless, it sits in a food matrix without tinting it and without catalysing the oxidation reactions that a soluble iron salt drives.Fits Flour, cereal, pasta and infant food fortification, and dry supplement blends where colour stability over a long shelf life is the governing constraint. It is the sort of material a formulator reaches for when the finished product is pale, fatty or stored for a year.Trade-off The properties that make it inert in the pack also mean it depends entirely on stomach acid to release any iron at all, and particle size, which is not on the label, governs how readily that happens. It is a fortification material more than a therapeutic-dose one. No human outcome trial is carried on this row.
IEIron-enriched yeastSaccharomyces cerevisiae grown in a medium rich in an iron salt, then washed, inactivated and dried, so that the iron ends up carried within the yeast biomass and associated with its proteins and other cell constituents rather than sitting in the capsule as a free salt. The finished powder is a low-percentage iron material with the colour, smell and taste of dried yeast.Fits Whole-food and food-state positioning lines, low-dose daily multivitamins and prenatal formats aimed at shoppers who prefer a food matrix on the panel. The yeast base also brings B vitamins and protein with it, which some brands count as part of the story rather than as a diluent.Trade-off The elemental iron share is low, so a therapeutic-size dose is impractical in this form and these products sit at maintenance levels. Yeast-derived material is a consideration for anyone avoiding yeast, and the iron content is set by a fermentation process that varies between producers. No human outcome trial is carried on this row.