Lactoferrin

Lactoferrin is a globular glycoprotein of roughly 80 kilodaltons that belongs to the transferrin family of iron-binding proteins ^[1]. Its single chain folds into two lobes, each able to hold an iron ion very tightly, and this structure gives the protein an unusually high affinity for iron along with the ability to bind and release it in response to conditions in the body ^[1]. It is present in many secretions, reaching its highest concentrations in colostrum and milk and appearing also in tears, saliva, and nasal fluid, and it is stored in the granules of neutrophils, where it takes part in the innate immune response ^[1][3].

The protein was first noted in milk in the late 1930s and characterized in detail around 1960, when its antibacterial action was linked to its capacity to bind iron ^[1][2]. Two broad kinds of activity have made it a focus of research. First, by sequestering iron it deprives many bacteria of a nutrient they need to grow, and it can also disrupt microbial membranes directly; fragments released when it is digested, known as lactoferricins, are even more strongly antimicrobial, and activity has been described against bacteria, fungi, and viruses ^[2][3]. Second, lactoferrin modulates the immune system and inflammation, and it can bind to surfaces and receptors that some pathogens use to enter cells ^[3][5].

These properties underlie a wide range of investigation into lactoferrin as a supplement and functional-food ingredient. A meta-analysis of randomized trials reported that lactoferrin supplementation was associated with a reduced risk of respiratory tract infections, and the protein has been studied in newborn care, iron status, and, more recently, as a candidate adjunct in viral illness ^[4][5]. Commercially, bovine lactoferrin is added to some infant formulas, yogurts, and other products and sold as a dietary supplement; because supplements are not held to the same manufacturing standards as medicines, the purity and content of such products can vary ^[4].

Generally well tolerated, with occasional mild GI complaints. Most products are derived from cow's milk, so people with dairy protein allergy should be careful. Long-term high-dose safety data in humans is still limited.