Ferric Ammonium Citrate Encyclopedia — Scientific Background

What Is Ferric Ammonium Citrate?

Ferric ammonium citrate (CAS 1185-57-5), also known as ammonium iron(III) citrate, ammonium ferric citrate, or iron ammonium citrate, is a complex salt of ill-defined structure composed of iron, ammonia, and citric acid. It is chemically characterized by the general formula C₆H₈O₇·xFe³⁺·yNH₃ and is available in two distinct forms:

The Two Forms: Brown vs. Green

Ferric ammonium citrate is commercially available in two distinct forms that differ in their iron content and are not interchangeable:

• Brown Ferric Ammonium Citrate — Contains approximately 16.5%–18.5% iron. This form is typically used in pharmaceutical applications and food fortification where higher iron concentration is desired.

• Green Ferric Ammonium Citrate — Contains approximately 14.5%–16.0% iron. This form is used in applications where a lower iron concentration is appropriate.

Physiological Functions of Iron

Iron is an essential trace mineral required for numerous physiological processes:

• Hemoglobin Synthesis — Iron is the central atom in the heme group of hemoglobin, enabling oxygen transport from the lungs to tissues

• Oxygen Transport — Iron-containing myoglobin facilitates oxygen storage and transport in muscle tissue

• Electron Transfer — Iron-sulfur clusters and heme groups participate in mitochondrial electron transport chain reactions

• Enzymatic Reactions — Iron is a cofactor for numerous enzymes involved in DNA synthesis, neurotransmitter production, and immune function

• Energy Metabolism — Iron-containing cytochromes are essential for ATP production

Mechanisms of Action and Absorption

Conventional Iron Absorption Pathway

Iron absorption from ferric ammonium citrate follows the normal physiological pathway for non-heme iron. Ferric iron (Fe³⁺) must first be reduced to ferrous iron (Fe²⁺) by duodenal cytochrome b (DcytB) or dietary reducing agents such as vitamin C before it can be transported across the enterocyte membrane by the divalent metal transporter 1 (DMT1). Once inside the enterocyte, iron is either stored as ferritin or transported across the basolateral membrane by ferroportin into the bloodstream, where it binds to transferrin for distribution to tissues.

The citrate component of ferric ammonium citrate enhances iron absorption by maintaining iron solubility in the alkaline environment of the small intestine and by facilitating iron uptake through the paracellular pathway.

liposomal Absorption Pathway

Liposomal encapsulation provides a fundamentally different absorption mechanism. The liposomal phospholipid bilayer is similar to cell membranes in the human body, which makes them progressively biocompatible. Enclosing iron in liposomes allows effective transport of iron to locations in the body where it is required, resulting in a high absorption rate and helping to reduce stomach upset. The liposomal delivery system bypasses the regulated DMT1 absorption pathway and provides an alternative route of cellular entry.

Brain Iron Delivery

Iron deficiency in children can have significant neurological consequences, and iron supplementation is an effective treatment of choice. However, traditional routes of iron supplementation do not allow efficient iron delivery to the brain due to the presence of the blood-brain barrier. A nanoliposomal formulation of ferric ammonium citrate (FAC-LIP) with 97% encapsulation efficiency and 40 nm particle size significantly increased iron content in the olfactory bulb, cerebral cortex, striatum, cerebellum, and hippocampus following intranasal delivery in rats, and was more efficient at doing so than FAC alone. No signs of apoptosis or abnormal cell morphology were observed in the brain following FAC-LIP administration, suggesting that the formulation was not overtly toxic.

Regulatory Status

Ferric ammonium citrate holds a unique position as an ingredient permissible in both food and pharmaceutical products.

United States (FDA)

In the United States, ferric ammonium citrate is listed in the Code of Federal Regulations (CFR) Title 21. Specifically, 21 CFR 184.1150 affirms it as Generally Recognized as Safe (GRAS) for use as a nutrient supplement. It is also approved as an anti-caking agent in salt for human consumption, with a maximum permitted level of 0.0025% (25 parts per million). The specifications for the food-grade material are outlined in the Food Chemicals Codex (FCC).

European Union (EFSA)

In the European Union, ferric ammonium citrate is an authorized food additive with the designated E-number E381. The European Food Safety Authority (EFSA) has evaluated its safety and established an Acceptable Daily Intake (ADI) for iron from all sources. Its use is permitted in specific food categories and at maximum levels as defined in Regulation (EC) No 1333/2008.

China

In China, ferric ammonium citrate is used as a food additive and nutritional fortificant (iron source) for cereal products, beverages, dairy products, and other foods to supplement trace element iron. The addition amount must comply with relevant food regulations and standards (such as GB 14880 or the Codex Alimentarius), typically expressed as a mass fraction (e.g., 0.05%–0.3%), adjusted according to the food matrix.

Liposomal Ferric Ammonium Citrate

Liposomal encapsulation of ferric ammonium citrate provides a fundamentally different delivery mechanism from conventional forms. The phospholipid bilayer surrounds the iron-citrate complex, forming a shield that protects it from gastric acid degradation and prevents premature reactions with food components. This delivery system:

• Protects iron from substances within the digestive system that may degrade the active ingredient and reduce absorption

• Achieves high encapsulation efficiency (97%) and small particle size (40 nm)

• Enhances intestinal absorption through lipid-mediated pathways

• Reduces gastrointestinal side effects by minimizing direct mucosal contact

• Enables efficient brain iron delivery following intranasal administration

Clinical Evidence

Nanoliposomal Ferric Ammonium Citrate for Brain Iron Delivery

A study published in the Journal of Nanobiotechnology (2017) developed and characterized a nanovesicular formulation of ferric ammonium citrate (FAC-LIP) and demonstrated that it can increase brain iron levels in rats following nasal administration. FAC was incorporated into liposomes with high efficiency (97%) and the liposomes were small (40 nm) and stable. Following intranasal delivery in rats, FAC-LIP significantly increased the iron content in the olfactory bulb, cerebral cortex, striatum, cerebellum, and hippocampus, and was more efficient at doing so than FAC alone. No signs of apoptosis or abnormal cell morphology were observed in the brain following FAC-LIP administration, and there were no significant changes in the levels of SOD and MDA, except in the cerebellum and hippocampus. No obvious morphological changes were observed in lung epithelial cells or tracheal mucosa after nasal delivery, suggesting that the formulation was not overtly toxic.

Iron Liposomes for Exercise-Induced Anemia

A study published in 2014 evaluated the encapsulation of iron in liposomes for improving the efficiency of iron supplementation in strenuously exercised rats. Rats with confirmed anemia were exercised for two weeks while receiving iron supplements by intragastric administration of ferric ammonium citrate (FAC) liposomes or heme iron liposomes. The results demonstrated that iron liposomes can efficiently relieve iron deficiency in strenuously exercised rats and may potentially be used as an effective iron supplement.

Safety and Regulatory

Ferric ammonium citrate has a favorable safety profile based on available data. According to safety data sheets, the compound is classified as having no significant hazard based on available data, and the classification criteria are not met under Regulation (EC) No 1907/2006. The European Food Safety Authority (EFSA) has evaluated its safety and established an Acceptable Daily Intake (ADI) for iron from all sources.

Liposomal encapsulation helps reduce the gastrointestinal side effects commonly associated with conventional iron salts, including nausea, cramping, and constipation. Iron status should be monitored through hemoglobin, ferritin, and transferrin saturation to guide dosing, as even well-tolerated forms should not be supplemented without confirmed deficiency due to the risks of iron overload.

Ferric ammonium citrate is widely commercialized as a dietary supplement ingredient, pharmaceutical agent, and food additive. It is Generally Recognized As Safe (GRAS) by the FDA for use as a nutrient supplement and is an authorized food additive (E381) in the European Union. Testing protocols must adhere to international standards including USP, Food Chemicals Codex (FCC), European Pharmacopoeia, and FAO/WHO Codex Alimentarius. Formulators should verify local regulatory requirements prior to market entry.

This product is intended for research, nutraceutical, and functional food applications. Not intended to diagnose, treat, cure, or prevent any disease.

69$/KG

69$/KG

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