Lactoferrin is an iron-binding protein from the transferrin family. First identified in bovine milk in 1939 and later isolated from human milk, it is a glycoprotein, meaning it is a protein with an attached sugar molecule. This structure is fundamental to its functions. While first found in milk, lactoferrin is also produced by mucosal epithelial cells and is present in various biological fluids.
Natural Sources and Bodily Functions
Lactoferrin is most concentrated in human colostrum, the first milk produced after giving birth, where levels can be as high as 7 grams per liter. This concentration decreases to about 1-2 grams per liter in mature breast milk. The high amount in early milk provides an advantage to newborns, contributing to their initial immune defenses. This protein’s presence is not limited to milk; it is a component of the innate immune system found at various mucosal surfaces.
It is secreted in tears, saliva, nasal secretions, and bronchial fluids, acting as a first line of defense against airborne and ingested pathogens. The protein is also released by neutrophils, a type of white blood cell, at sites of infection.
Immune System Support
The immune-supporting role of lactoferrin is multifaceted, involving direct actions against pathogens and modulation of the body’s own immune responses. Its best-known antimicrobial action is its ability to bind strongly to iron. This process, known as iron sequestration, deprives many species of bacteria of the iron they require to grow and replicate, an effect described as bacteriostatic. By limiting the availability of this nutrient, lactoferrin helps control the proliferation of harmful bacteria.
Beyond this, lactoferrin can exert a direct bactericidal, or bacteria-killing, effect. It can bind to the surface of certain bacteria, specifically to lipopolysaccharides in their outer membranes. This interaction disrupts the membrane’s integrity, leading to the breakdown and death of the bacterial cell. This mechanism is effective against a range of bacteria, including Helicobacter pylori, where bovine lactoferrin has been noted to be particularly potent.
Its activity extends to viruses and fungi as well. Lactoferrin can interfere with the initial stages of a viral infection by binding to viral particles or to the host cell receptors that viruses use to gain entry. This can prevent viruses, such as some herpes viruses, from successfully infecting cells. The protein also exhibits antifungal properties against yeasts like Candida albicans through direct interaction with the fungal cell surface. Lactoferrin also helps regulate the immune system by influencing the activity of immune cells and modulating cytokine expression to prevent excessive inflammation.
Role in Iron Regulation
The “ferrin” in lactoferrin highlights its specific relationship with iron, a function that is distinct from its immune activities but complementary to them. The protein’s structure features two lobes, each capable of binding one iron ion (Fe3+). It has an exceptionally high affinity for iron, approximately 300 times greater than that of transferrin, the primary iron-transport protein in the blood. This strong binding capacity is enhanced in slightly acidic environments, which often occur at sites of inflammation.
Lactoferrin also plays a part in the body’s iron metabolism. It assists in the transport and absorption of iron in the intestine, helping the body’s cells receive the iron they need. This can improve overall iron status and help protect against deficiency. By binding to iron and facilitating its controlled uptake, lactoferrin helps prevent the negative effects of free iron, which can be reactive and contribute to cellular damage if not properly managed.
Commercial Applications and Supplementation
Lactoferrin’s properties have led to its use in commercial products, mainly as bovine lactoferrin derived from cow’s milk. Bovine and human lactoferrin are structurally and functionally similar, with their amino acid sequences sharing a high degree of homology. A primary application is its addition to infant formulas to more closely mimic human breast milk. This provides infants support for immune system development and helps establish a healthy gut microbiome.
For adults, lactoferrin is available as a dietary supplement, marketed for its immune-supporting and gut health benefits. Research has explored its use for health concerns, including skin conditions. Bovine lactoferrin is recognized as safe (GRAS) in the United States for use in supplements and foods. The European Food Safety Authority has also concluded that it is safe for its proposed uses, including in infant formula and food supplements. Dosing for supplements can vary, with recommendations for adults ranging from 250 to 500 mg per day.