Ferrous fumarate vs ferrous sulphate: choosing an iron source for fortification

Ferrous fumarate and ferrous sulphate are the two iron salts most often used to fortify flour and foods, and both are on the list of iron compounds the WHO recommends for low-extraction (white) wheat flour. Choosing between them comes down to the food you are fortifying, how it is stored, and the rules in your market.

This guide compares them on the points that matter to a formulator or a buyer.

At a glance

	Ferrous fumarate	Ferrous sulphate (dried)	Ferrous sulphate heptahydrate
Formula	C4H2FeO4	FeSO4·H2O	FeSO4·7H2O
Elemental iron	32.9%	32.9%	20.1%
Appearance	Reddish-brown powder	Greyish-white to buff powder	Light green crystals
Water solubility	Slightly soluble	Freely soluble (slowly)	Freely soluble
Effect on food	Fewer colour and flavour changes	More likely to cause changes	More likely to cause changes
WHO-recommended for white wheat flour	Yes	Yes	Yes

Iron percentages are calculated from each compound's molecular weight.

Iron content: the same, if you compare like with like

Ferrous fumarate and dried ferrous sulphate carry almost exactly the same amount of iron: about 32.9% by weight. The common belief that ferrous fumarate is "stronger" comes from comparing it with ferrous sulphate heptahydrate, which carries seven molecules of water and only about 20% iron.

So for the same iron, you need roughly 1.6 times as much heptahydrate as either of the other two. For dry premixes and flour, where iron is bought and dosed by content, that difference shows up in material, packing and freight.

Solubility and what it does to food

This is the biggest practical difference.

Ferrous sulphate dissolves freely in water. That makes it easy to use in liquids and solutions, but in stored cereal foods soluble iron is more reactive: it can cause colour changes and off-flavours, a known issue with soluble iron compounds in fortified cereals.

Ferrous fumarate is only slightly soluble in water. It dissolves in dilute acid, such as stomach acid, which is how the body still takes up its iron. In food, its low solubility means it causes fewer changes to colour and flavour during storage. That is why it has been used in products such as infant cereals and maize flour.

It is not perfect for every product: in cocoa-based drink powders, ferrous fumarate can discolour the drink when it is made with boiling liquid. Always test the finished product.

Absorption

In adults, the iron in ferrous fumarate is absorbed about as well as the iron in ferrous sulphate, which is the reference compound researchers measure other iron salts against.

In young children, absorption from ferrous fumarate has been measured lower, probably because of lower stomach acid. Even so, complementary foods fortified with ferrous fumarate have been shown to improve infants' iron status. Adding ascorbic acid (vitamin C) improves absorption from both.

Fortification levels

The WHO and its partners recommend the same added iron levels for ferrous fumarate and ferrous sulphate in low-extraction wheat flour, set by how much flour people eat:

Average flour intake per person	Added iron
Less than 75 g a day	60 ppm
75–149 g a day	60 ppm
150–300 g a day	30 ppm
More than 300 g a day	20 ppm

National standards set their own levels. In India, FSSAI permits both ferrous fumarate and ferrous sulphate for fortified atta and maida (28–42.5 mg of iron per kg) and for double fortified salt (850–1100 ppm of iron). Ferrous sulphate is not a permitted iron source for fortified rice.

Regulatory status

Both are well established. In the US, both are affirmed as Generally Recognized as Safe: ferrous fumarate under 21 CFR 184.1307d and ferrous sulphate under 21 CFR 184.1315. In the EU, both are permitted forms of iron for fortified foods and food supplements.

How to choose

Dry foods with a long shelf life (cereals, flour, noodles, bakery mixes): ferrous fumarate usually keeps colour and flavour better.
Liquids, solutions and syrups: ferrous sulphate dissolves readily.
Dry premixes and feed, bought by iron content: dried ferrous sulphate or ferrous fumarate, both at about 32.9% iron, rather than the heptahydrate.
A mandated programme: check which compounds your national standard permits for that food first.

Whichever you choose, run a storage trial on the finished product and confirm the grade your market requires: IP, BP, EP or USP for medicines, FCC for food, or Feed.

Agarwal Life Sciences manufactures Ferrous Fumarate, Ferrous Sulphate Monohydrate and Ferrous Sulphate Heptahydrate, so we can supply whichever suits your product, with samples and a certificate of analysis on request.

Frequently asked questions

Is ferrous fumarate better than ferrous sulphate?

Neither is better in every case. Ferrous fumarate causes fewer colour and flavour changes in dry foods during storage; ferrous sulphate dissolves freely, which suits liquids and solutions. In adults their iron is absorbed about equally well.

Which has more iron, ferrous fumarate or ferrous sulphate?

Ferrous fumarate and dried ferrous sulphate (the monohydrate) both carry about 32.9% iron by weight. Ferrous sulphate heptahydrate carries about 20.1%, because of its extra water.

Can ferrous fumarate and ferrous sulphate be used in the same flour?

The WHO recommends the same added iron levels for both in low-extraction wheat flour, so a mill can choose either to meet a standard. National regulations, such as FSSAI in India, list the permitted sources for each food.

Is ferrous sulphate allowed in fortified rice in India?

No. FSSAI permits ferrous sulphate for fortified atta, maida, double fortified salt and cereal products, but fortified rice must use ferric pyrophosphate or sodium iron EDTA.