Is lactoferrin a protein?

Yes. It is a glycoprotein of roughly 80 kilodaltons, made of a single polypeptide chain folded into two lobes, with sugar groups attached. It belongs to the transferrin family of iron-binding proteins.

Where does lactoferrin come from?

In the body it is produced by glandular epithelial cells and by neutrophils. It occurs in milk, most abundantly in colostrum, and in tears, saliva, nasal and intestinal secretions. Supplements are made from bovine milk or whey.

What does lactoferrin bind?

Each of its two lobes binds one ferric iron ion, together with a carbonate ion. It holds iron considerably more tightly than serum transferrin does, and retains it in acidic conditions where transferrin would release it.

What is lactoferrin? Structure, sources and function

An iron-binding protein of milk and mucosal secretions, and one of the few proteins most people meet before they are a day old.

Lactoferrin is a glycoprotein of roughly 80 kilodaltons, built from a single polypeptide chain that folds into two lobes of similar architecture. It belongs to the transferrin family, a group of proteins defined by their capacity to bind iron.

What it binds, and how tightly

Each lobe holds one ferric iron ion. The binding also requires a carbonate ion, which sits in the site alongside the metal. What distinguishes lactoferrin from its relatives is the strength of that grip and its persistence: serum transferrin releases its iron as acidity rises, which is how iron is delivered inside cells, whereas lactoferrin holds on well into acidic conditions.

The protein exists in two visible states. Iron-free lactoferrin, called the apo form, is colorless. The iron-saturated holo form carries a distinct salmon color, which is why the earlier literature refers to the red protein of milk.

Where it occurs

Lactoferrin is produced by glandular epithelial cells and released into the fluids those glands secrete: milk, tears, saliva, nasal and bronchial secretions, and intestinal fluid. Concentration in milk is highest in colostrum and falls substantially as lactation continues.

It is also stored in the secondary granules of neutrophils and released when those cells degranulate at a site of inflammation. That second origin is what makes it measurable as a marker of intestinal inflammation, covered in the biomarker section.

What it is understood to do

The best-characterized action follows from the iron binding. By holding iron in a form bacteria cannot use, lactoferrin restricts the growth of organisms that depend on it. Separate work describes actions that do not involve iron, including direct interaction with bacterial surfaces.

What follows from any of that for a person taking a supplement is a different question, and the answer varies considerably by claim. The benefits section takes each one separately and grades it.

This page reports published research. It is general information, not medical advice, and not a recommendation to take anything. Lactoferrin supplements are derived from cow's milk and are unsuitable for anyone with a milk protein allergy. Anyone who is pregnant, breastfeeding, treating an infant, or managing a diagnosed condition should speak to a clinician first.