Whey protein is a source of all 9 of the essential amino acids. They are required from the diet because the body cannot make them. During infection, the body will take these amino acids from tissues like muscle in order to provide those building blocks for synthesis of components of the immune system.
The subset of the essential amino acids, branched chain amino acids, are particularly useful for the immune system. Whey is the richest natural source of the BCAA. They have been shown to be required for immune cells to proliferate and can be oxidised by immune cells. The BCAA can provide nitrogen precursors for the amino acid glutamine.
Whey also contains glutamine itself. It is used as a fuel by the immune system and to make nucleotides, along with other important cellular functions such as amino acid metabolism, heat shock protein (HSP) expression and glutathione mediated antioxidant defence.
Whey proteins are the milk proteins richest in sulfur amino acids (cysteine and methionine). Methionine is an essential amino acid, whereas cysteine is part of the main antioxidant in the body’s cells, glutathione. Methionine can also be converted to cysteine.
Glutathione is oxidised with exercise. Maintaining glutathione levels contributes to the natural internal antioxidant stores that help buffer against the free radicals (oxidative stress) generated by exercise.
Infections can also increase free radical production. Glutathione also plays a role in many cellular processes including those of the immune system, such as the activation of T-lymphocytes and polymorphonuclear leukocytes, cell proliferation and cytokine production.
Whey supplementation has been shown to increase glutathione levels in the body.
Immunoglobulin proteins enable the immune system to recognise specific parts (antigens) of foreign microbes. Antibodies to antigens of pathogenic bacteria and viruses are present in cow’s milk, this functions to provide passive immunity to the calf. But they can also be potentially beneficial for humans. A pool of antibodies that inhibit rotavirus has been found in whey. Bovine immunoglobulins could have effects on inflammation by binding bacteria and bacterial lipopolysaccharide (LPS) in the gut and preventing their interaction with the intestinal epithelium.
Lactoferrin is a multifunctional protein that is not degraded during digestion. It has binding sites that enable it to interact with cells in the gut. It binds iron, which can restrict bacterial growth. It also binds LPS, and viral membranes, preventing entry of viruses into cells.
Together, Igs and lactoferrin may act synergistically to modify immune activation and subsequent inflammation.